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  • Calculating rotation in > 360 deg. situations

    - by danglebrush
    I'm trying to work out a problem I'm having with degrees. I have data that is a list of of angles, in standard degree notation -- e.g. 26 deg. Usually when dealing with angles, if an angle exceeds 360 deg then the angle continues around and effectively "resets" -- i.e. the angle "starts again", e.g. 357 deg, 358 deg, 359 deg, 0 deg, 1 deg, etc. What I want to happen is the degree to continue increasing -- i.e. 357 deg, 358 deg, 359 deg, 360 deg, 361 deg, etc. I want to modify my data so that I have this converted data in it. When numbers approach the 0 deg limit, I want them to become negative -- i.e. 3 deg, 2 deg, 1 deg, 0 deg, -1 deg, -2 deg, etc. With multiples of 360 deg (both positive and negative), I want the degrees to continue, e.g. 720 deg, etc. Any suggestions on what approach to take? There is, no doubt, a frustratingly simple way of doing this, but my current solution is kludgey to say the least .... ! My best attempt to date is to look at the percentage difference between angle n and angle n - 1. If this is a large difference -- e.g. 60% -- then this needs to be modified, by adding or subtracting 360 deg to the current value, depending on the previous angle value. That is, if the previous angle is negative, substract 360, and add 360 if the previous angle is positive. Any suggestions on improving this? Any improvements?

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  • Simple Physics Simulation in java not working.

    - by Static Void Main
    Dear experts, I wanted to implement ball physics and as i m newbie, i adapt the code in tutorial http://adam21.web.officelive.com/Documents/JavaPhysicsTutorial.pdf . i try to follow that as i much as i can, but i m not able to apply all physical phenomenon in code, can somebody please tell me, where i m mistaken or i m still doing some silly programming mistake. The balls are moving when i m not calling bounce method and i m unable to avail the bounce method and ball are moving towards left side instead of falling/ending on floor**, Can some body recommend me some better way or similar easy compact way to accomplish this task of applying physics on two ball or more balls with interactivity. here is code ; import java.awt.*; public class AdobeBall { protected int radius = 20; protected Color color; // ... Constants final static int DIAMETER = 40; // ... Instance variables private int m_x; // x and y coordinates upper left private int m_y; private double dx = 3.0; // delta x and y private double dy = 6.0; private double m_velocityX; // Pixels to move each time move() is called. private double m_velocityY; private int m_rightBound; // Maximum permissible x, y values. private int m_bottomBound; public AdobeBall(int x, int y, double velocityX, double velocityY, Color color1) { super(); m_x = x; m_y = y; m_velocityX = velocityX; m_velocityY = velocityY; color = color1; } public double getSpeed() { return Math.sqrt((m_x + m_velocityX - m_x) * (m_x + m_velocityX - m_x) + (m_y + m_velocityY - m_y) * (m_y + m_velocityY - m_y)); } public void setSpeed(double speed) { double currentSpeed = Math.sqrt(dx * dx + dy * dy); dx = dx * speed / currentSpeed; dy = dy * speed / currentSpeed; } public void setDirection(double direction) { m_velocityX = (int) (Math.cos(direction) * getSpeed()); m_velocityY = (int) (Math.sin(direction) * getSpeed()); } public double getDirection() { double h = ((m_x + dx - m_x) * (m_x + dx - m_x)) + ((m_y + dy - m_y) * (m_y + dy - m_y)); double a = (m_x + dx - m_x) / h; return a; } // ======================================================== setBounds public void setBounds(int width, int height) { m_rightBound = width - DIAMETER; m_bottomBound = height - DIAMETER; } // ============================================================== move public void move() { double gravAmount = 0.02; double gravDir = 90; // The direction for the gravity to be in. // ... Move the ball at the give velocity. m_x += m_velocityX; m_y += m_velocityY; // ... Bounce the ball off the walls if necessary. if (m_x < 0) { // If at or beyond left side m_x = 0; // Place against edge and m_velocityX = -m_velocityX; } else if (m_x > m_rightBound) { // If at or beyond right side m_x = m_rightBound; // Place against right edge. m_velocityX = -m_velocityX; } if (m_y < 0) { // if we're at top m_y = 0; m_velocityY = -m_velocityY; } else if (m_y > m_bottomBound) { // if we're at bottom m_y = m_bottomBound; m_velocityY = -m_velocityY; } // double speed = Math.sqrt((m_velocityX * m_velocityX) // + (m_velocityY * m_velocityY)); // ...Friction stuff double fricMax = 0.02; // You can use any number, preferably less than 1 double friction = getSpeed(); if (friction > fricMax) friction = fricMax; if (m_velocityX >= 0) { m_velocityX -= friction; } if (m_velocityX <= 0) { m_velocityX += friction; } if (m_velocityY >= 0) { m_velocityY -= friction; } if (m_velocityY <= 0) { m_velocityY += friction; } // ...Gravity stuff m_velocityX += Math.cos(gravDir) * gravAmount; m_velocityY += Math.sin(gravDir) * gravAmount; } public Color getColor() { return color; } public void setColor(Color newColor) { color = newColor; } // ============================================= getDiameter, getX, getY public int getDiameter() { return DIAMETER; } public double getRadius() { return radius; // radius should be a local variable in Ball. } public int getX() { return m_x; } public int getY() { return m_y; } } using adobeBall: import java.awt.*; import java.awt.event.*; import javax.swing.*; public class AdobeBallImplementation implements Runnable { private static final long serialVersionUID = 1L; private volatile boolean Play; private long mFrameDelay; private JFrame frame; private MyKeyListener pit; /** true means mouse was pressed in ball and still in panel. */ private boolean _canDrag = false; private static final int MAX_BALLS = 50; // max number allowed private int currentNumBalls = 2; // number currently active private AdobeBall[] ball = new AdobeBall[MAX_BALLS]; public AdobeBallImplementation(Color ballColor) { frame = new JFrame("simple gaming loop in java"); frame.setSize(400, 400); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); pit = new MyKeyListener(); pit.setPreferredSize(new Dimension(400, 400)); frame.setContentPane(pit); ball[0] = new AdobeBall(34, 150, 7, 2, Color.YELLOW); ball[1] = new AdobeBall(50, 50, 5, 3, Color.BLUE); frame.pack(); frame.setVisible(true); frame.setBackground(Color.white); start(); frame.addMouseListener(pit); frame.addMouseMotionListener(pit); } public void start() { Play = true; Thread t = new Thread(this); t.start(); } public void stop() { Play = false; } public void run() { while (Play == true) { // bounce(ball[0],ball[1]); runball(); pit.repaint(); try { Thread.sleep(mFrameDelay); } catch (InterruptedException ie) { stop(); } } } public void drawworld(Graphics g) { for (int i = 0; i < currentNumBalls; i++) { g.setColor(ball[i].getColor()); g.fillOval(ball[i].getX(), ball[i].getY(), 40, 40); } } public double pointDistance (double x1, double y1, double x2, double y2) { return Math.sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1)); } public void runball() { while (Play == true) { try { for (int i = 0; i < currentNumBalls; i++) { for (int j = 0; j < currentNumBalls; j++) { if (pointDistance(ball[i].getX(), ball[i].getY(), ball[j].getX(), ball[j].getY()) < ball[i] .getRadius() + ball[j].getRadius() + 2) { // bounce(ball[i],ball[j]); ball[i].setBounds(pit.getWidth(), pit.getHeight()); ball[i].move(); pit.repaint(); } } } try { Thread.sleep(50); } catch (Exception e) { System.exit(0); } } catch (Exception e) { e.printStackTrace(); } } } public static double pointDirection(int x1, int y1, int x2, int y2) { double H = Math.sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1)); // The // hypotenuse double x = x2 - x1; // The opposite double y = y2 - y1; // The adjacent double angle = Math.acos(x / H); angle = angle * 57.2960285258; if (y < 0) { angle = 360 - angle; } return angle; } public static void bounce(AdobeBall b1, AdobeBall b2) { if (b2.getSpeed() == 0 && b1.getSpeed() == 0) { // Both balls are stopped. b1.setDirection(pointDirection(b1.getX(), b1.getY(), b2.getX(), b2 .getY())); b2.setDirection(pointDirection(b2.getX(), b2.getY(), b1.getX(), b1 .getY())); b1.setSpeed(1); b2.setSpeed(1); } else if (b2.getSpeed() == 0 && b1.getSpeed() != 0) { // B1 is moving. B2 is stationary. double angle = pointDirection(b1.getX(), b1.getY(), b2.getX(), b2 .getY()); b2.setSpeed(b1.getSpeed()); b2.setDirection(angle); b1.setDirection(angle - 90); } else if (b1.getSpeed() == 0 && b2.getSpeed() != 0) { // B1 is moving. B2 is stationary. double angle = pointDirection(b2.getX(), b2.getY(), b1.getX(), b1 .getY()); b1.setSpeed(b2.getSpeed()); b1.setDirection(angle); b2.setDirection(angle - 90); } else { // Both balls are moving. AdobeBall tmp = b1; double angle = pointDirection(b2.getX(), b2.getY(), b1.getX(), b1 .getY()); double origangle = b1.getDirection(); b1.setDirection(angle + origangle); angle = pointDirection(tmp.getX(), tmp.getY(), b2.getX(), b2.getY()); origangle = b2.getDirection(); b2.setDirection(angle + origangle); } } public static void main(String[] args) { javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { new AdobeBallImplementation(Color.red); } }); } } *EDIT:*ok splitting the code using new approach for gravity from this forum: this code also not working the ball is not coming on floor: public void mymove() { m_x += m_velocityX; m_y += m_velocityY; if (m_y + m_bottomBound > 400) { m_velocityY *= -0.981; // setY(400 - m_bottomBound); m_y = 400 - m_bottomBound; } // ... Bounce the ball off the walls if necessary. if (m_x < 0) { // If at or beyond left side m_x = 0; // Place against edge and m_velocityX = -m_velocityX; } else if (m_x > m_rightBound) { // If at or beyond right side m_x = m_rightBound - 20; // Place against right edge. m_velocityX = -m_velocityX; } if (m_y < 0) { // if we're at top m_y = 1; m_velocityY = -m_velocityY; } else if (m_y > m_bottomBound) { // if we're at bottom m_y = m_bottomBound - 20; m_velocityY = -m_velocityY; } } thanks a lot for any correction and help. jibby

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  • My raycaster is putting out strange results, how do I fix it?

    - by JamesK89
    I'm working on a raycaster in ActionScript 3.0 for the fun of it, and as a learning experience. I've got it up and running and its displaying me output as expected however I'm getting this strange bug where rays go through corners of blocks and the edges of blocks appear through walls. Maybe somebody with more experience can point out what I'm doing wrong or maybe a fresh pair of eyes can spot a tiny bug I haven't noticed. Thank you so much for your help! Screenshots: http://i55.tinypic.com/25koebm.jpg http://i51.tinypic.com/zx5jq9.jpg Relevant code: function drawScene() { rays.graphics.clear(); rays.graphics.lineStyle(1, rgba(0x00,0x66,0x00)); var halfFov = (player.fov/2); var numRays:int = ( stage.stageWidth / COLUMN_SIZE ); var prjDist = ( stage.stageWidth / 2 ) / Math.tan(toRad( halfFov )); var angStep = ( player.fov / numRays ); for( var i:int = 0; i < numRays; i++ ) { var rAng = ( ( player.angle - halfFov ) + ( angStep * i ) ) % 360; if( rAng < 0 ) rAng += 360; var ray:Object = castRay(player.position, rAng); drawRaySlice(i*COLUMN_SIZE, prjDist, player.angle, ray); } } function drawRaySlice(sx:int, prjDist, angle, ray:Object) { if( ray.distance >= MAX_DIST ) return; var height:int = int(( TILE_SIZE / (ray.distance * Math.cos(toRad(angle-ray.angle))) ) * prjDist); if( !height ) return; var yTop = int(( stage.stageHeight / 2 ) - ( height / 2 )); if( yTop < 0 ) yTop = 0; var yBot = int(( stage.stageHeight / 2 ) + ( height / 2 )); if( yBot > stage.stageHeight ) yBot = stage.stageHeight; rays.graphics.moveTo( (ray.origin.x / TILE_SIZE) * MINI_SIZE, (ray.origin.y / TILE_SIZE) * MINI_SIZE ); rays.graphics.lineTo( (ray.hit.x / TILE_SIZE) * MINI_SIZE, (ray.hit.y / TILE_SIZE) * MINI_SIZE ); for( var x:int = 0; x < COLUMN_SIZE; x++ ) { for( var y:int = yTop; y < yBot; y++ ) { buffer.setPixel(sx+x, y, clrTable[ray.tile-1] >> ( ray.horz ? 1 : 0 )); } } } function castRay(origin:Point, angle):Object { // Return values var rTexel = 0; var rHorz = false; var rTile = 0; var rDist = MAX_DIST + 1; var rMap:Point = new Point(); var rHit:Point = new Point(); // Ray angle and slope var ra = toRad(angle) % ANGLE_360; if( ra < ANGLE_0 ) ra += ANGLE_360; var rs = Math.tan(ra); var rUp = ( ra > ANGLE_0 && ra < ANGLE_180 ); var rRight = ( ra < ANGLE_90 || ra > ANGLE_270 ); // Ray position var rx = 0; var ry = 0; // Ray step values var xa = 0; var ya = 0; // Ray position, in map coordinates var mx:int = 0; var my:int = 0; var mt:int = 0; // Distance var dx = 0; var dy = 0; var ds = MAX_DIST + 1; // Horizontal intersection if( ra != ANGLE_180 && ra != ANGLE_0 && ra != ANGLE_360 ) { ya = ( rUp ? TILE_SIZE : -TILE_SIZE ); xa = ya / rs; ry = int( origin.y / TILE_SIZE ) * ( TILE_SIZE ) + ( rUp ? TILE_SIZE : -1 ); rx = origin.x + ( ry - origin.y ) / rs; mx = 0; my = 0; while( mx >= 0 && my >= 0 && mx < world.size.x && my < world.size.y ) { mx = int( rx / TILE_SIZE ); my = int( ry / TILE_SIZE ); mt = getMapTile(mx,my); if( mt > 0 && mt < 9 ) { dx = rx - origin.x; dy = ry - origin.y; ds = ( dx * dx ) + ( dy * dy ); if( rDist >= MAX_DIST || ds < rDist ) { rDist = ds; rTile = mt; rMap.x = mx; rMap.y = my; rHit.x = rx; rHit.y = ry; rHorz = true; rTexel = int(rx % TILE_SIZE) } break; } rx += xa; ry += ya; } } // Vertical intersection if( ra != ANGLE_90 && ra != ANGLE_270 ) { xa = ( rRight ? TILE_SIZE : -TILE_SIZE ); ya = xa * rs; rx = int( origin.x / TILE_SIZE ) * ( TILE_SIZE ) + ( rRight ? TILE_SIZE : -1 ); ry = origin.y + ( rx - origin.x ) * rs; mx = 0; my = 0; while( mx >= 0 && my >= 0 && mx < world.size.x && my < world.size.y ) { mx = int( rx / TILE_SIZE ); my = int( ry / TILE_SIZE ); mt = getMapTile(mx,my); if( mt > 0 && mt < 9 ) { dx = rx - origin.x; dy = ry - origin.y; ds = ( dx * dx ) + ( dy * dy ); if( rDist >= MAX_DIST || ds < rDist ) { rDist = ds; rTile = mt; rMap.x = mx; rMap.y = my; rHit.x = rx; rHit.y = ry; rHorz = false; rTexel = int(ry % TILE_SIZE); } break; } rx += xa; ry += ya; } } return { angle: angle, distance: Math.sqrt(rDist), hit: rHit, map: rMap, tile: rTile, horz: rHorz, origin: origin, texel: rTexel }; }

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  • PHP mtChart (new pChart): how do i control the angle of x-axis labels?

    - by gsquare567
    i am trying to graph the results of a survey, where the question is multiple choice. eg. How would you describe this website? format: option | number of times selected | percentage of users who selected that option Informative 1 50% All of the above 1 50% Interesting 0 0% Intelligent 0 0% Cool 0 0% Incredible 0 0% Sleek 0 0% Amazing the graph is a bar graph, where each bar represents one of those options, and the height of the bar depends on the number of times selected. however, the labels are slanted at a 45 degree angle and are barely readable! here is my code: <?php require_once ("includes/common.php"); require_once ("graph/mtChart.min.php"); // type must be specified $type = $_GET['type']; if($type == "surveys_report_MC_or_CB") { // PARAMS $surveyID = $_GET['surveyID']; $questionID = $_GET['questionID']; // END PARAMS $question = SurveyQuestions::getSingle($questionID); $answers = SurveyAnswers::getAll($questionID); $options = SurveyQuestionOptions::getAll($question[SurveyQuestions::surveyQuestionID]); $others = SurveyAnswers::setOptionCounts($options, $answers); $printedOthers = false; // set graph $values = array(); $axisLabels = array(); foreach($options as $option) { $values[$option[SurveyQuestionOptions::optionText]] = $option['count']; $axisLabels[] = $option[SurveyQuestionOptions::optionText]; } $graphs = array(); $graphs[0] = $values; $xName = "Option"; $yName = "Number of Times Selected"; $graphTitle = $question[SurveyQuestions::question]; $series = array("Total"); $showLegend = false; $tall = false; } drawGraph($graphs, $axisLabels, $xName, $yName, $graphTitle, $series, $showLegend, $tall); function drawGraph($graphs, $axisLabels, $xName, $yName, $graphTitle, $series, $showLegend, $tall) { $Graph = ($tall) ? new mtChart(575,375) : new mtChart(575,275); // Dataset definition $avg = 0; $i = 0; foreach ($graphs as $key => $value) { $Graph->AddPoint($value,"series" . $key); $Graph->SetSerieName($series[$key],"series" . $key); // Get average $avg += array_sum($value); $size = sizeof($value); $i += $size; // Calculate x-axis tick interval $step = ceil($size / 25); } $Graph->AddPoint($axisLabels,"XLabel"); $Graph->AddAllSeries(); $Graph->RemoveSerie("XLabel"); $Graph->SetAbsciseLabelSerie("XLabel"); $Graph->SetXAxisName($xName); $Graph->SetYAxisName($yName); // Get from cache if it exists $Graph->enableCaching(NULL, 'graph/cache/'); $Graph->GetFromCache(); // Initialize the graph $Graph->setInterval($step); $Graph->setFontProperties("graph/tahoma.ttf",8); ($showLegend) ? $Graph->setGraphArea(45,30,475,200) : $Graph->setGraphArea(75,30,505,200); $Graph->drawGraphArea(255,255,255,TRUE); $Graph->drawScale(SCALE_START0,100,100,100,TRUE,55,1,TRUE); $Graph->drawGrid(4,TRUE,230,230,230,50); // Draw the 0 line $Graph->setFontProperties("graph/tahoma.ttf",6); $Graph->drawTreshold(0,143,55,72,TRUE,TRUE); // Draw the bar graph $Graph->drawBarGraph(); // Draw average line $Graph->drawTreshold($avg/$i, 0, 0, 0, FALSE, FALSE, 5); // Finish the graph $Graph->setFontProperties("graph/tahoma.ttf",8); if ($showLegend) { $Graph->drawLegend(482,30,255,255,255,255,255,255,100,100,100); } $Graph->setFontProperties("graph/tahoma.ttf",10); $Graph->drawTitle(0,22,$graphTitle,100,100,100,555); // Draw Graph $Graph->Stroke(); } and here is where i use it on the page: <div class="graph_container"> <img src="drawGraph.php?type=surveys_report_MC_or_CB&surveyID=<?php echo $survey[Surveys::surveyID] ?>&questionID=<?php echo $question[SurveyQuestions::surveyQuestionID] ?>" /> is there a setting i can apply to the graph which will make the text look nicer, or at least let me set the angle to 90 degrees so people can read it if they cock their head to the left? thanks! btw, mtchart is located here: http://code.google.com/p/mtchart/ and pchart (the original, which has mainly the same code) is here: http://pchart.sourceforge.net/documentation.php

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  • Drawing text at an angle (e.g. upside down) in Android

    - by Damian
    I'm trying to build a custom clock view in Android. See image http://twitpic.com/1devk7 So far to draw the time and hour markers I have been using the Canvas.rotate method to get the desired effect. However, notice that it is difficult to interpret the numbers in the lower half of the clock (e.g. 6 or 9?) because of the angle in which they are drawn. When using drawText, is it possible to draw the text at 45/90/180 degrees so that all text appears upright when my onDraw method has finished?

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  • Understanding CABasicAnimation when spinning an object from a random angle....

    - by user157733
    I have spent ages trying to figure this out and I am still having problems. I want to rotate an image a random number of time - say 5 and a bit - then have it stop. I then want to rotate it again FROM ITS STOPPED POSITION. I am having difficulty with this so maybe someone can advise me on the right way to do it. Ok so I am using a CABasicAnimation for the spin like this... CABasicAnimation* rotationAnimation; rotationAnimation = [NSNumber numberWithFloat: 0.0]; rotationAnimation.toValue = [NSNumber numberWithFloat: M_PI * 1.0]; rotationAnimation.duration = 100; rotationAnimation.cumulative = YES; rotationAnimation.repeatCount = 5.2; rotationAnimation.removedOnCompletion = NO; rotationAnimation.fillMode = kCAFillModeForwards; [myView.layer addAnimation:rotationAnimation forKey:@"rotationAnimation"]; This works fine. I use a animationDidStop function to transform the image to the new angle so that it actually in the new position (not just appearing that way). This is where my problems start. I have tried the following... removing the toValue line which means the animation starts from where it currently is but when the animation block is repeated it jumps back to this start position every time the block is run storing the value of the end rotation and using this in the toValue so the 2 lines of code become... rotationAnimation = [NSNumber numberWithFloat: previousVal]; rotationAnimation.toValue = [NSNumber numberWithFloat: (M_PI * 1.0)+previousVal]; when I do this the animation still jumps because it is flicking back to the previousVal everytime the block is repeated Therefore my final thought is to check to see if the image is at zero, if not then rotate it to zero, then impliment the block of code to spin multiple times. This seems complicated but is this the ONLY way to achieve this? I am concerned about getting the timings smooth with this method. Any suggestions would be amazing! Thanks

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  • Help Understanding Function

    - by Fred F.
    What does the following function perform? public static double CleanAngle(double angle) { while (angle < 0) angle += 2 * System.Math.PI; while (angle > 2 * System.Math.PI) angle -= 2 * System.Math.PI; return angle; } This is how it is used with ATan2. I believe the actually values passed to ATan2 are always positive. static void Main(string[] args) { int q = 1; //'x- and y-coordinates will always be positive values //'therefore, do i need to "clean"? foreach (Point oPoint in new Point[] { new Point(8,20), new Point(-8,20), new Point(8,-20), new Point(-8,-20)}) { Debug.WriteLine(Math.Atan2(oPoint.Y, oPoint.X), "unclean " + q.ToString()); Debug.WriteLine(CleanAngle(Math.Atan2(oPoint.Y, oPoint.X)), "cleaned " + q.ToString()); q++; } //'output //'unclean 1: 1.19028994968253 //'cleaned 1: 1.19028994968253 //'unclean 2: 1.95130270390726 //'cleaned 2: 1.95130270390726 //'unclean 3: -1.19028994968253 //'cleaned 3: 5.09289535749705 //'unclean 4: -1.95130270390726 //'cleaned 4: 4.33188260327232 }

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  • Rotate on hover using Jquery

    - by Ian34
    I can't figure out how to set up a jquery rotate function that would only rotate on hover. Here is the code that I am using: $('div.settingsButton').hover(function() { var angle = 0; setInterval(function() { angle += 4; $(this).rotate(angle); }, 50); }, function() { var angle = 0; setInterval(function() { angle = 0; $(this).rotate(angle); }, 50); }); The rotate is a plugin found here: http://code.google.com/p/jqueryrotate/

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  • Applications: The mathematics of movement, Part 1

    - by TechTwaddle
    Before you continue reading this post, a suggestion; if you haven’t read “Programming Windows Phone 7 Series” by Charles Petzold, go read it. Now. If you find 150+ pages a little too long, at least go through Chapter 5, Principles of Movement, especially the section “A Brief Review of Vectors”. This post is largely inspired from this chapter. At this point I assume you know what vectors are, how they are represented using the pair (x, y), what a unit vector is, and given a vector how you would normalize the vector to get a unit vector. Our task in this post is simple, a marble is drawn at a point on the screen, the user clicks at a random point on the device, say (destX, destY), and our program makes the marble move towards that point and stop when it is reached. The tricky part of this task is the word “towards”, it adds a direction to our problem. Making a marble bounce around the screen is simple, all you have to do is keep incrementing the X and Y co-ordinates by a certain amount and handle the boundary conditions. Here, however, we need to find out exactly how to increment the X and Y values, so that the marble appears to move towards the point where the user clicked. And this is where vectors can be so helpful. The code I’ll show you here is not ideal, we’ll be working with C# on Windows Mobile 6.x, so there is no built-in vector class that I can use, though I could have written one and done all the math inside the class. I think it is trivial to the actual problem that we are trying to solve and can be done pretty easily once you know what’s going on behind the scenes. In other words, this is an excuse for me being lazy. The first approach, uses the function Atan2() to solve the “towards” part of the problem. Atan2() takes a point (x, y) as input, Atan2(y, x), note that y goes first, and then it returns an angle in radians. What angle you ask. Imagine a line from the origin (0, 0), to the point (x, y). The angle which Atan2 returns is the angle the positive X-axis makes with that line, measured clockwise. The figure below makes it clear, wiki has good details about Atan2(), give it a read. The pair (x, y) also denotes a vector. A vector whose magnitude is the length of that line, which is Sqrt(x*x + y*y), and a direction ?, as measured from positive X axis clockwise. If you’ve read that chapter from Charles Petzold’s book, this much should be clear. Now Sine and Cosine of the angle ? are special. Cosine(?) divides x by the vectors length (adjacent by hypotenuse), thus giving us a unit vector along the X direction. And Sine(?) divides y by the vectors length (opposite by hypotenuse), thus giving us a unit vector along the Y direction. Therefore the vector represented by the pair (cos(?), sin(?)), is the unit vector (or normalization) of the vector (x, y). This unit vector has a length of 1 (remember sin2(?) + cos2(?) = 1 ?), and a direction which is the same as vector (x, y). Now if I multiply this unit vector by some amount, then I will always get a point which is a certain distance away from the origin, but, more importantly, the point will always be on that line. For example, if I multiply the unit vector with the length of the line, I get the point (x, y). Thus, all we have to do to move the marble towards our destination point, is to multiply the unit vector by a certain amount each time and draw the marble, and the marble will magically move towards the click point. Now time for some code. The application, uses a timer based frame draw method to draw the marble on the screen. The timer is disabled initially and whenever the user clicks on the screen, the timer is enabled. The callback function for the timer follows the standard Update and Draw cycle. private double totLenToTravelSqrd = 0; private double startPosX = 0, startPosY = 0; private double destX = 0, destY = 0; private void Form1_MouseUp(object sender, MouseEventArgs e) {     destX = e.X;     destY = e.Y;     double x = marble1.x - destX;     double y = marble1.y - destY;     //calculate the total length to be travelled     totLenToTravelSqrd = x * x + y * y;     //store the start position of the marble     startPosX = marble1.x;     startPosY = marble1.y;     timer1.Enabled = true; } private void timer1_Tick(object sender, EventArgs e) {     UpdatePosition();     DrawMarble(); } Form1_MouseUp() method is called when ever the user touches and releases the screen. In this function we save the click point in destX and destY, this is the destination point for the marble and we also enable the timer. We store a few more values which we will use in the UpdatePosition() method to detect when the marble has reached the destination and stop the timer. So we store the start position of the marble and the square of the total length to be travelled. I’ll leave out the term ‘sqrd’ when speaking of lengths from now on. The time out interval of the timer is set to 40ms, thus giving us a frame rate of about ~25fps. In the timer callback, we update the marble position and draw the marble. We know what DrawMarble() does, so here, we’ll only look at how UpdatePosition() is implemented; private void UpdatePosition() {     //the vector (x, y)     double x = destX - marble1.x;     double y = destY - marble1.y;     double incrX=0, incrY=0;     double distanceSqrd=0;     double speed = 6;     //distance between destination and current position, before updating marble position     distanceSqrd = x * x + y * y;     double angle = Math.Atan2(y, x);     //Cos and Sin give us the unit vector, 6 is the value we use to magnify the unit vector along the same direction     incrX = speed * Math.Cos(angle);     incrY = speed * Math.Sin(angle);     marble1.x += incrX;     marble1.y += incrY;     //check for bounds     if ((int)marble1.x < MinX + marbleWidth / 2)     {         marble1.x = MinX + marbleWidth / 2;     }     else if ((int)marble1.x > (MaxX - marbleWidth / 2))     {         marble1.x = MaxX - marbleWidth / 2;     }     if ((int)marble1.y < MinY + marbleHeight / 2)     {         marble1.y = MinY + marbleHeight / 2;     }     else if ((int)marble1.y > (MaxY - marbleHeight / 2))     {         marble1.y = MaxY - marbleHeight / 2;     }     //distance between destination and current point, after updating marble position     x = destX - marble1.x;     y = destY - marble1.y;     double newDistanceSqrd = x * x + y * y;     //length from start point to current marble position     x = startPosX - (marble1.x);     y = startPosY - (marble1.y);     double lenTraveledSqrd = x * x + y * y;     //check for end conditions     if ((int)lenTraveledSqrd >= (int)totLenToTravelSqrd)     {         System.Console.WriteLine("Stopping because destination reached");         timer1.Enabled = false;     }     else if (Math.Abs((int)distanceSqrd - (int)newDistanceSqrd) < 4)     {         System.Console.WriteLine("Stopping because no change in Old and New position");         timer1.Enabled = false;     } } Ok, so in this function, first we subtract the current marble position from the destination point to give us a vector. The first three lines of the function construct this vector (x, y). The vector (x, y) has the same length as the line from (marble1.x, marble1.y) to (destX, destY) and is in the direction pointing from (marble1.x, marble1.y) to (destX, destY). Note that marble1.x and marble1.y denote the center point of the marble. Then we use Atan2() to get the angle which this vector makes with the positive X axis and use Cosine() and Sine() of that angle to get the unit vector along that same direction. We multiply this unit vector with 6, to get the values which the position of the marble should be incremented by. This variable, speed, can be experimented with and determines how fast the marble moves towards the destination. After this, we check for bounds to make sure that the marble stays within the screen limits and finally we check for the end condition and stop the timer. The end condition has two parts to it. The first case is the normal case, where the user clicks well inside the screen. Here, we stop when the total length travelled by the marble is greater than or equal to the total length to be travelled. Simple enough. The second case is when the user clicks on the very corners of the screen. Like I said before, the values marble1.x and marble1.y denote the center point of the marble. When the user clicks on the corner, the marble moves towards the point, and after some time tries to go outside of the screen, this is when the bounds checking comes into play and corrects the marble position so that the marble stays inside the screen. In this case the marble will never travel a distance of totLenToTravelSqrd, because of the correction is its position. So here we detect the end condition when there is not much change in marbles position. I use the value 4 in the second condition above. After experimenting with a few values, 4 seemed to work okay. There is a small thing missing in the code above. In the normal case, case 1, when the update method runs for the last time, marble position over shoots the destination point. This happens because the position is incremented in steps (which are not small enough), so in this case too, we should have corrected the marble position, so that the center point of the marble sits exactly on top of the destination point. I’ll add this later and update the post. This has been a pretty long post already, so I’ll leave you with a video of how this program looks while running. Notice in the video that the marble moves like a bot, without any grace what so ever. And that is because the speed of the marble is fixed at 6. In the next post we will see how to make the marble move a little more elegantly. And also, if Atan2(), Sine() and Cosine() are a little too much to digest, we’ll see how to achieve the same effect without using them, in the next to next post maybe. Ciao!

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  • rotate player based off of joystick

    - by pengume
    Hey everyone I have this game that i am making in android and I have a touch screen joystick that moves the player around based on the joysticks position. I cant figure out how to also get the player to rotate at the same angle of the joystick. so when the joystick is to the left the players bitmap is rotated to the left as well. Maybe someone here has some sample code I could look at here is the joysticks class that I am using. `public class GameControls implements OnTouchListener { public float initx = DroidzActivity.screenWidth - 45; //255; // 320 og 425 public float inity = DroidzActivity.screenHeight - 45;//425; // 480 og 267 public Point _touchingPoint = new Point( DroidzActivity.screenWidth - 45, DroidzActivity.screenHeight - 45); public Point _pointerPosition = new Point(DroidzActivity.screenWidth - 100, DroidzActivity.screenHeight - 100); // ogx 220 ogy 150 private Boolean _dragging = false; private boolean attackMode = false; @Override public boolean onTouch(View v, MotionEvent event) { update(event); return true; } private MotionEvent lastEvent; public boolean ControlDragged; private static double angle; public void update(MotionEvent event) { if (event == null && lastEvent == null) { return; } else if (event == null && lastEvent != null) { event = lastEvent; } else { lastEvent = event; } // drag drop if (event.getAction() == MotionEvent.ACTION_DOWN) { if ((int) event.getX() > 0 && (int) event.getX() < 50 && (int) event.getY() > DroidzActivity.screenHeight - 160 && (int) event.getY() < DroidzActivity.screenHeight - 0) { setAttackMode(true); } else { _dragging = true; } } else if (event.getAction() == MotionEvent.ACTION_UP) { if(isAttackMode()){ setAttackMode(false); } _dragging = false; } if (_dragging) { ControlDragged = true; // get the pos _touchingPoint.x = (int) event.getX(); _touchingPoint.y = (int) event.getY(); // Log.d("GameControls", "x = " + _touchingPoint.x + " y = " //+ _touchingPoint.y); // bound to a box if (_touchingPoint.x < DroidzActivity.screenWidth - 75) { // og 400 _touchingPoint.x = DroidzActivity.screenWidth - 75; } if (_touchingPoint.x > DroidzActivity.screenWidth - 15) {// og 450 _touchingPoint.x = DroidzActivity.screenWidth - 15; } if (_touchingPoint.y < DroidzActivity.screenHeight - 75) {// og 240 _touchingPoint.y = DroidzActivity.screenHeight - 75; } if (_touchingPoint.y > DroidzActivity.screenHeight - 15) {// og 290 _touchingPoint.y = DroidzActivity.screenHeight - 15; } // get the angle setAngle(Math.atan2(_touchingPoint.y - inity, _touchingPoint.x - initx) / (Math.PI / 180)); // Move the ninja in proportion to how far // the joystick is dragged from its center _pointerPosition.y += Math.sin(getAngle() * (Math.PI / 180)) * (_touchingPoint.x / 70); // og 180 70 _pointerPosition.x += Math.cos(getAngle() * (Math.PI / 180)) * (_touchingPoint.x / 70); // make the pointer go thru if (_pointerPosition.x > DroidzActivity.screenWidth) { _pointerPosition.x = 0; } if (_pointerPosition.x < 0) { _pointerPosition.x = DroidzActivity.screenWidth; } if (_pointerPosition.y > DroidzActivity.screenHeight) { _pointerPosition.y = 0; } if (_pointerPosition.y < 0) { _pointerPosition.y = DroidzActivity.screenHeight; } } else if (!_dragging) { ControlDragged = false; // Snap back to center when the joystick is released _touchingPoint.x = (int) initx; _touchingPoint.y = (int) inity; // shaft.alpha = 0; } } public void setAttackMode(boolean attackMode) { this.attackMode = attackMode; } public boolean isAttackMode() { return attackMode; } public void setAngle(double angle) { this.angle = angle; } public static double getAngle() { return angle; } }` I should also note that the player has animations based on when he is moving or attacking.

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  • Relative cam movement and momentum on arbitrary surface

    - by user29244
    I have been working on a game for quite long, think sonic classic physics in 3D or tony hawk psx, with unity3D. However I'm stuck at the most fundamental aspect of movement. The requirement is that I need to move the character in mario 64 fashion (or sonic adventure) aka relative cam input: the camera's forward direction always point input forward the screen, left or right input point toward left or right of the screen. when input are resting, the camera direction is independent from the character direction and the camera can orbit the character when input are pressed the character rotate itself until his direction align with the direction the input is pointing at. It's super easy to do as long your movement are parallel to the global horizontal (or any world axis). However when you try to do this on arbitrary surface (think moving along complex curved surface) with the character sticking to the surface normal (basically moving on wall and ceiling freely), it seems harder. What I want is to achieve the same finesse of movement than in mario but on arbitrary angled surfaces. There is more problem (jumping and transitioning back to the real world alignment and then back on a surface while keeping momentum) but so far I didn't even take off the basics. So far I have accomplish moving along the curved surface and the relative cam input, but for some reason direction fail all the time (point number 3, the character align slowly to the input direction). Do you have an idea how to achieve that? Here is the code and some demo so far: The demo: https://dl.dropbox.com/u/24530447/flash%20build/litesonicengine/LiteSonicEngine5.html Camera code: using UnityEngine; using System.Collections; public class CameraDrive : MonoBehaviour { public GameObject targetObject; public Transform camPivot, camTarget, camRoot, relcamdirDebug; float rot = 0; //---------------------------------------------------------------------------------------------------------- void Start() { this.transform.position = targetObject.transform.position; this.transform.rotation = targetObject.transform.rotation; } void FixedUpdate() { //the pivot system camRoot.position = targetObject.transform.position; //input on pivot orientation rot = 0; float mouse_x = Input.GetAxisRaw( "camera_analog_X" ); // rot = rot + ( 0.1f * Time.deltaTime * mouse_x ); // wrapAngle( rot ); // //when the target object rotate, it rotate too, this should not happen UpdateOrientation(this.transform.forward,targetObject.transform.up); camRoot.transform.RotateAround(camRoot.transform.up,rot); //debug the relcam dir RelativeCamDirection() ; //this camera this.transform.position = camPivot.position; //set the camera to the pivot this.transform.LookAt( camTarget.position ); // } //---------------------------------------------------------------------------------------------------------- public float wrapAngle ( float Degree ) { while (Degree < 0.0f) { Degree = Degree + 360.0f; } while (Degree >= 360.0f) { Degree = Degree - 360.0f; } return Degree; } private void UpdateOrientation( Vector3 forward_vector, Vector3 ground_normal ) { Vector3 projected_forward_to_normal_surface = forward_vector - ( Vector3.Dot( forward_vector, ground_normal ) ) * ground_normal; camRoot.transform.rotation = Quaternion.LookRotation( projected_forward_to_normal_surface, ground_normal ); } float GetOffsetAngle( float targetAngle, float DestAngle ) { return ((targetAngle - DestAngle + 180)% 360) - 180; } //---------------------------------------------------------------------------------------------------------- void OnDrawGizmos() { Gizmos.DrawCube( camPivot.transform.position, new Vector3(1,1,1) ); Gizmos.DrawCube( camTarget.transform.position, new Vector3(1,5,1) ); Gizmos.DrawCube( camRoot.transform.position, new Vector3(1,1,1) ); } void OnGUI() { GUI.Label(new Rect(0,80,1000,20*10), "targetObject.transform.up : " + targetObject.transform.up.ToString()); GUI.Label(new Rect(0,100,1000,20*10), "target euler : " + targetObject.transform.eulerAngles.y.ToString()); GUI.Label(new Rect(0,100,1000,20*10), "rot : " + rot.ToString()); } //---------------------------------------------------------------------------------------------------------- void RelativeCamDirection() { float input_vertical_movement = Input.GetAxisRaw( "Vertical" ), input_horizontal_movement = Input.GetAxisRaw( "Horizontal" ); Vector3 relative_forward = Vector3.forward, relative_right = Vector3.right, relative_direction = ( relative_forward * input_vertical_movement ) + ( relative_right * input_horizontal_movement ) ; MovementController MC = targetObject.GetComponent<MovementController>(); MC.motion = relative_direction.normalized * MC.acceleration * Time.fixedDeltaTime; MC.motion = this.transform.TransformDirection( MC.motion ); //MC.transform.Rotate(Vector3.up, input_horizontal_movement * 10f * Time.fixedDeltaTime); } } Mouvement code: using UnityEngine; using System.Collections; public class MovementController : MonoBehaviour { public float deadZoneValue = 0.1f, angle, acceleration = 50.0f; public Vector3 motion ; //-------------------------------------------------------------------------------------------- void OnGUI() { GUILayout.Label( "transform.rotation : " + transform.rotation ); GUILayout.Label( "transform.position : " + transform.position ); GUILayout.Label( "angle : " + angle ); } void FixedUpdate () { Ray ground_check_ray = new Ray( gameObject.transform.position, -gameObject.transform.up ); RaycastHit raycast_result; Rigidbody rigid_body = gameObject.rigidbody; if ( Physics.Raycast( ground_check_ray, out raycast_result ) ) { Vector3 next_position; //UpdateOrientation( gameObject.transform.forward, raycast_result.normal ); UpdateOrientation( gameObject.transform.forward, raycast_result.normal ); next_position = GetNextPosition( raycast_result.point ); rigid_body.MovePosition( next_position ); } } //-------------------------------------------------------------------------------------------- private void UpdateOrientation( Vector3 forward_vector, Vector3 ground_normal ) { Vector3 projected_forward_to_normal_surface = forward_vector - ( Vector3.Dot( forward_vector, ground_normal ) ) * ground_normal; transform.rotation = Quaternion.LookRotation( projected_forward_to_normal_surface, ground_normal ); } private Vector3 GetNextPosition( Vector3 current_ground_position ) { Vector3 next_position; // //-------------------------------------------------------------------- // angle = 0; // Vector3 dir = this.transform.InverseTransformDirection(motion); // angle = Vector3.Angle(Vector3.forward, dir);// * 1f * Time.fixedDeltaTime; // // if(angle > 0) this.transform.Rotate(0,angle,0); // //-------------------------------------------------------------------- next_position = current_ground_position + gameObject.transform.up * 0.5f + motion ; return next_position; } } Some observation: I have the correct input, I have the correct translation in the camera direction ... but whenever I attempt to slowly lerp the direction of the character in direction of the input, all I get is wild spin! Sad Also discovered that strafing to the right (immediately at the beginning without moving forward) has major singularity trapping on the equator!! I'm totally lost and crush (I have already done a much more featured version which fail at the same aspect)

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  • CW/CCW Rotation of a Vector

    - by user23132
    Considering that I have a vector A, and after an arbitrary rotation I get vector B. I want to use this rotation operation in others vectors as well, but I'm having problems in doing that. My idea do that is to calculate the perpendicular vector C of the plane AB (by calculating AxB). This vector C is the axis that I'll need to rotate. To discover the angle I used the dot product between A and B, the acos of the dot product will return the lowest angle between A and B, the angle ang. The rotation I need to do is then: -rotate *ang*º around the C axis. The problem is that I dont know if this rotation is a CW or CCW rotation, since the cos of the dot product does not give me information of the sign of the angle. There's a tip discover that in 2D ( A.x * B.y - A.y * B.x) that you can use to discover if the vector A is at left/right of vector B. But I dont know how to do this in 3D space. Can anyone help me?

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  • Bump mapping Problem GLSL

    - by jmfel1926
    I am having a slight problem with my Bump Mapping project. Although everything works OK (at least from what I know) there is a slight mistake somewhere and I get incorrect shading on the brick wall when the light goes to the one side or the other as seen in the picture below: The light is on the right side so the shading on the wall should be the other way. I have provided the shaders to help find the issue (I do not have much experience with shaders). Shaders: varying vec3 viewVec; varying vec3 position; varying vec3 lightvec; attribute vec3 tangent; attribute vec3 binormal; uniform vec3 lightpos; uniform mat4 cameraMat; void main() { gl_TexCoord[0] = gl_MultiTexCoord0; gl_Position = ftransform(); position = vec3(gl_ModelViewMatrix * gl_Vertex); lightvec = vec3(cameraMat * vec4(lightpos,1.0)) - position ; vec3 eyeVec = vec3(gl_ModelViewMatrix * gl_Vertex); viewVec = normalize(-eyeVec); } uniform sampler2D colormap; uniform sampler2D normalmap; varying vec3 viewVec; varying vec3 position; varying vec3 lightvec; vec3 vv; uniform float diffuset; uniform float specularterm; uniform float ambientterm; void main() { vv=viewVec; vec3 normals = normalize(texture2D(normalmap,gl_TexCoord[0].st).rgb * 2.0 - 1.0); normals.y = -normals.y; //normals = (normals * gl_NormalMatrix).xyz ; vec3 distance = lightvec; float dist_number =length(distance); float final_dist_number = 2.0/pow(dist_number,diffuset); vec3 light_dir=normalize(lightvec); vec3 Halfvector = normalize(light_dir+vv); float angle=max(dot(Halfvector,normals),0.0); angle= pow(angle,specularterm); vec3 specular=vec3(angle,angle,angle); float diffuseterm=max(dot(light_dir,normals),0.0); vec3 diffuse = diffuseterm * texture2D(colormap,gl_TexCoord[0].st).rgb; vec3 ambient = ambientterm *texture2D(colormap,gl_TexCoord[0].st).rgb; vec3 diffusefinal = diffuse * final_dist_number; vec3 finalcolor=diffusefinal+specular+ambient; gl_FragColor = vec4(finalcolor, 1.0); }

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  • C++: Checking if an object faces a point (within a certain range)

    - by bojoradarial
    I have been working on a shooter game in C++, and am trying to add a feature whereby missiles shot must be within 90 degrees (PI/2 radians) of the direction the ship is facing. The missiles will be shot towards the mouse. My idea is that the ship's angle of rotation is compared with the angle between the ship and the mouse (std::atan2(mouseY - shipY, mouseX - shipX)), and if the difference is less than PI/4 (45 degrees) then the missile can be fired. However, I can't seem to get this to work. The ship's angle of rotation is increased and decreased with the A and D keys, so it is possible that it isn't between 0 and 2*PI, hence the use of fmod() below. Code: float userRotation = std::fmod(user->Angle(), 6.28318f); if (std::abs(userRotation - missileAngle) > 0.78f) return; Any help would be appreciated. Thanks!

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  • How to Point sprite's direction towards Mouse or an Object [duplicate]

    - by Irfan Dahir
    This question already has an answer here: Rotating To Face a Point 1 answer I need some help with rotating sprites towards the mouse. I'm currently using the library allegro 5.XX. The rotation of the sprite works but it's constantly inaccurate. It's always a few angles off from the mouse to the left. Can anyone please help me with this? Thank you. P.S I got help with the rotating function from here: http://www.gamefromscratch.com/post/2012/11/18/GameDev-math-recipes-Rotating-to-face-a-point.aspx Although it's by javascript, the maths function is the same. And also, by placing: if(angle < 0) { angle = 360 - (-angle); } doesn't fix it. The Code: #include <allegro5\allegro.h> #include <allegro5\allegro_image.h> #include "math.h" int main(void) { int width = 640; int height = 480; bool exit = false; int shipW = 0; int shipH = 0; ALLEGRO_DISPLAY *display = NULL; ALLEGRO_EVENT_QUEUE *event_queue = NULL; ALLEGRO_BITMAP *ship = NULL; if(!al_init()) return -1; display = al_create_display(width, height); if(!display) return -1; al_install_keyboard(); al_install_mouse(); al_init_image_addon(); al_set_new_bitmap_flags(ALLEGRO_MIN_LINEAR | ALLEGRO_MAG_LINEAR); //smoother rotate ship = al_load_bitmap("ship.bmp"); shipH = al_get_bitmap_height(ship); shipW = al_get_bitmap_width(ship); int shipx = width/2 - shipW/2; int shipy = height/2 - shipH/2; int mx = width/2; int my = height/2; al_set_mouse_xy(display, mx, my); event_queue = al_create_event_queue(); al_register_event_source(event_queue, al_get_mouse_event_source()); al_register_event_source(event_queue, al_get_keyboard_event_source()); //al_hide_mouse_cursor(display); float angle; while(!exit) { ALLEGRO_EVENT ev; al_wait_for_event(event_queue, &ev); if(ev.type == ALLEGRO_EVENT_KEY_UP) { switch(ev.keyboard.keycode) { case ALLEGRO_KEY_ESCAPE: exit = true; break; /*case ALLEGRO_KEY_LEFT: degree -= 10; break; case ALLEGRO_KEY_RIGHT: degree += 10; break;*/ case ALLEGRO_KEY_W: shipy -=10; break; case ALLEGRO_KEY_S: shipy +=10; break; case ALLEGRO_KEY_A: shipx -=10; break; case ALLEGRO_KEY_D: shipx += 10; break; } }else if(ev.type == ALLEGRO_EVENT_MOUSE_AXES) { mx = ev.mouse.x; my = ev.mouse.y; angle = atan2(my - shipy, mx - shipx); } // al_draw_bitmap(ship,shipx, shipy, 0); //al_draw_rotated_bitmap(ship, shipW/2, shipH/2, shipx, shipy, degree * 3.142/180,0); al_draw_rotated_bitmap(ship, shipW/2, shipH/2, shipx, shipy,angle, 0); //I directly placed the angle because the allegro library calculates radians, and if i multiplied it by 180/3. 142 the rotation would go hawire, not would, it actually did. al_flip_display(); al_clear_to_color(al_map_rgb(0,0,0)); } al_destroy_bitmap(ship); al_destroy_event_queue(event_queue); al_destroy_display(display); return 0; } EDIT: This was marked duplicate by a moderator. I'd like to say that this isn't the same as that. I'm a total beginner at game programming, I had a view at that other topic and I had difficulty understanding it. Please understand this, thank you. :/ Also, while I was making a print of what the angle is I got this... Here is a screenshot:http://img34.imageshack.us/img34/7396/fzuq.jpg Which is weird because aren't angles supposed to be 360 degrees only?

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  • Rotation matrix for a 3D vector

    - by Shashwat
    I have a direction vector on which I have to apply some rotation to align it to positive z-axis. To use Matrix.CreateRotationX(angle) of XNA, I need the angle for which I'd have to compute cos or tan inverse. I think this is a complex task to do. Also, eventually those are also converted to sin(angle) and cos(angle) in the matrix. Is there any inbuilt way to create rotation matrix from a 3D vector? However, I can write the function but still asking if there is one already there.

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  • FPS camera specification

    - by user1095108
    I remember I once composed a FPS viewing transformation, as a composition of 3 rotations, each with an angle as a parameter. The first angle specified the left/right rotation around the y-axis, the second angle the up/down rotation around the x-axis, and the third around the z-axis. The viewing transformation was therefore specified by 3 angles. Naturally, this transformation had a gimbal lock, depending in what order the transformation were performed. What should I look at to derive my viewing transformation without the gimbal lock? I know the "lookAt" method already, but I consider that cumbersome. EDIT: MY first guess is to do the first 2 transformations to get a viewing direction and then the axis-angle rotation on this axis.

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  • Issues implementing arcball viewer

    - by Pris
    My scene has a simple cube, and a camera built with the lookAt function (I'm using OpenGL). The scene renders fine, and I'm sure I have my model/view/projection matrices set up correctly. Now I'm trying to implement arcball rotation for my camera, but I'm having some trouble. I've got it down to calculating the angle/axis rotation for a virtual sphere in normalized screen coordinates. That means when I move my mouse left to right, I get an angle around the Y axis... and moving my mouse up/down will get me an angle about X. I'm not sure where to go from here -- what do I need to do with my axis so I can apply the angle to simulate camera rotation about its viewpoint? If I try directly applying the axis/angle rotation the camera/view transform I get what you'd expect. The view is rotated about the world axes which the mouse moving over the virtual sphere on the screen corresponds to. So if I move the mouse up/down the view rotates about the world's X axis (what I get reminds me of a first-person view)... but this isn't what I want. I think I need the axis I get to be transformed so it passes through the camera viewpoint and is oriented correct in reference to the camera... but I don't know if that's right or how to do that.

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  • what's wrong with my lookAt and move forward code?

    - by alaslipknot
    so am still in the process of getting familiar with libGdx and one of the fun things i love to do is to make basics method for reusability on future projects, and for now am stacked on getting a Sprite rotate toward target (vector2) and then move forward based on that rotation the code am using is this : // set angle public void lookAt(Vector2 target) { float angle = (float) Math.atan2(target.y - this.position.y, target.x - this.position.x); angle = (float) (angle * (180 / Math.PI)); setAngle(angle); } // move forward public void moveForward() { this.position.x += Math.cos(getAngle())*this.speed; this.position.y += Math.sin(getAngle())*this.speed; } and this is my render method : @Override public void render(float delta) { // TODO Auto-generated method stub Gdx.gl.glClearColor(0, 0, 0.0f, 1); Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT); // groupUpdate(); Vector3 mousePos = new Vector3(Gdx.input.getX(), Gdx.input.getY(), 0); camera.unproject(mousePos); ball.lookAt(new Vector2(mousePos.x, mousePos.y)); // if (Gdx.input.isTouched()) { ball.moveForward(); } batch.begin(); batch.draw(ball.getSprite(), ball.getPos().x, ball.getPos().y, ball .getSprite().getOriginX(), ball.getSprite().getOriginY(), ball .getSprite().getWidth(), ball.getSprite().getHeight(), .5f, .5f, ball.getAngle()); batch.end(); } the goal is to make the ball always look at the mouse cursor, and then move forward when i click, am also using this camera : // create the camera and the SpriteBatch camera = new OrthographicCamera(); camera.setToOrtho(false, 800, 480); aaaand the result was so creepy lol Thank you

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  • This codes in Actionscript-2, Can anyone help me translate it into AS-3 please ?.......a newby pulli

    - by Spux
    this.createEmptyMovieClip('mask_mc',0); bg_mc.setMask(mask_mc); var contor:Number=0; // function drawCircle draws a circle on mask_mc MovieClip of radius r and having center to mouse coordinates function drawCircle(mask_mc:MovieClip):Void{ var r:Number = 20; var xcenter:Number = _xmouse; var ycenter:Number = _ymouse; var A:Number = Math.tan(22.5 * Math.PI/180); var endx:Number; var endy:Number; var cx:Number; var cy:Number; mask_mc.beginFill(0x000000, 100); mask_mc.moveTo(xcenter+r, ycenter); for (var angle:Number = Math.PI/4; angle<=2*Math.PI; angle += Math.PI/4) { xend = r*Math.cos(angle); yend = r*Math.sin(angle); xbegin =xend + r* A *Math.cos((angle-Math.PI/2)); ybegin =yend + r* A *Math.sin((angle-Math.PI/2)); mask_mc.curveTo(xbegin+xcenter, ybegin+ycenter, xend+xcenter, yend+ycenter); } mask_mc.endFill(); } // contor variable is used to hold if the mouse is pressed (contor is 1) or not (contor is 0) this.onMouseDown=function(){ drawCircle(mask_mc); contor=1; } // if the mouse is hold and moved then we draw a circle on the mask_mc this.onMouseMove=this.onEnterFrame=function(){ if (contor==1){ drawCircle(mask_mc); } } this.onMouseUp=function(){ contor=0; }

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  • Drawing an honeycomb with as3

    - by vitto
    Hi, I'm trying to create an honeycomb with as3 but I have some problem on cells positioning. I've already created the cells (not with code) and for cycled them to a funcion and send to it the parameters which what I thought was need (the honeycomb cell is allready on a sprite container in the center of the stage). to see the structure of the cycle and which parameters passes, please see the example below, the only thing i calculate in placeCell is the angle which I should obtain directly inside tha called function Note: the angle is reversed but it isn't important, and the color are useful in example only for visually divide cases. My for cycle calls placeCell and passes cell, current_case, counter (index) and the honeycomb cell_lv (cell level). I thought it was what i needed but I'm not skilled in geometry and trigonometry, so I don't know how to position cells correctly: function placeCell (cell:Sprite, current_case:int, counter:int, cell_lv:int):void { var margin:int = 2; var angle:Number = (360 / (cell_lv * 6)) * (current_case + counter); var radius:Number = (cell.width + margin) * cell_lv; cell.x = radius * Math.cos (angle); cell.y = radius * Math.sin (angle); trace ("LV " + cell_lv + " current_case " + current_case + " counter " + counter + " angle " + angle + " radius " + radius) } how can I do to solve it?

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  • How can I correctly calculate the direction for a moving object?

    - by Jakub Hampl
    I'm solving the following problem: I have an object and I know its position now and its position 300ms ago. I assume the object is moving. I have a point to which I want the object to get. What I need is to get the angle from my current object to the destination point in such a format that I know whether to turn left or right. The idea is to assume the current angle from the last known position and the current position. I'm trying to solve this in MATLAB. I've tried using several variations with atan2 but either I get the wrong angle in some situations (like when my object is going in circles) or I get the wrong angle in all situations. Examples of code that screws up: a = new - old; b = dest - new; alpha = atan2(a(2) - b(2), a(1) - b(1); where new is the current position (eg. x = 40; y = 60; new = [x y];), old is the 300ms old position and dest is the destination point. Edit Here's a picture to demonstrate the problem with a few examples: In the above image there are a few points plotted and annotated. The black line indicates our estimated current facing of the object. If the destination point is dest1 I would expect an angle of about 88°. If the destination point is dest2 I would expect an angle of about 110°. If the destination point is dest3 I would expect an angle of about -80°.

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  • How can I scale movement physics functions to frames per second (in a game engine)?

    - by Richard
    I am working on a game in Javascript (HTML5 Canvas). I implemented a simple algorithm that allows an object to follow another object with basic physics mixed in (a force vector to drive the object in the right direction, and the velocity stacks momentum, but is slowed by a constant drag force). At the moment, I set it up as a rectangle following the mouse (x, y) coordinates. Here's the code: // rectangle x, y position var x = 400; // starting x position var y = 250; // starting y position var FPS = 60; // frames per second of the screen // physics variables: var velX = 0; // initial velocity at 0 (not moving) var velY = 0; // not moving var drag = 0.92; // drag force reduces velocity by 8% per frame var force = 0.35; // overall force applied to move the rectangle var angle = 0; // angle in which to move // called every frame (at 60 frames per second): function update(){ // calculate distance between mouse and rectangle var dx = mouseX - x; var dy = mouseY - y; // calculate angle between mouse and rectangle var angle = Math.atan(dy/dx); if(dx < 0) angle += Math.PI; else if(dy < 0) angle += 2*Math.PI; // calculate the force (on or off, depending on user input) var curForce; if(keys[32]) // SPACE bar curForce = force; // if pressed, use 0.35 as force else curForce = 0; // otherwise, force is 0 // increment velocty by the force, and scaled by drag for x and y velX += curForce * Math.cos(angle); velX *= drag; velY += curForce * Math.sin(angle); velY *= drag; // update x and y by their velocities x += velX; y += velY; And that works fine at 60 frames per second. Now, the tricky part: my question is, if I change this to a different framerate (say, 30 FPS), how can I modify the force and drag values to keep the movement constant? That is, right now my rectangle (whose position is dictated by the x and y variables) moves at a maximum speed of about 4 pixels per second, and accelerates to its max speed in about 1 second. BUT, if I change the framerate, it moves slower (e.g. 30 FPS accelerates to only 2 pixels per frame). So, how can I create an equation that takes FPS (frames per second) as input, and spits out correct "drag" and "force" values that will behave the same way in real time? I know it's a heavy question, but perhaps somebody with game design experience, or knowledge of programming physics can help. Thank you for your efforts. jsFiddle: http://jsfiddle.net/BadDB

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  • Angle between two 2d vectors, diff between two methods?

    - by Sean Ochoa
    Hey all. I've got this code snippet, and I'm wondering why the results of the first method differ from the results of the second method, given the same input? public double AngleBetween_1(vector a, vector b) { var dotProd = a.Dot(b); var lenProd = a.Len*b.Len; var divOperation = dotProd/lenProd; return Math.Acos(divOperation) * (180.0 / Math.PI); } public double AngleBetween_2(vector a, vector b) { var dotProd = a.Dot(b); var lenProd = a.Len*b.Len; var divOperation = dotProd/lenProd; return (1/Math.Cos(divOperation)) * (180.0 / Math.PI); }

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