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• Eculidean space and vector magnitude

  - by Starkers

  Below we have distances from the origin calculated in two different ways, giving the Euclidean distance, the Manhattan distance and the Chebyshev distance. Euclidean distance is what we use to calculate the magnitude of vectors in 2D/3D games, and that makes sense to me: Let's say we have a vector that gives us the range a spaceship with limited fuel can travel. If we calculated this with Manhattan metric, our ship could travel a distance of X if it were travelling horizontally or vertically, however the second it attempted to travel diagonally it could only tavel X/2! So like I say, Euclidean distance does make sense. However, I still don't quite get how we calculate 'real' distances from the vector's magnitude. Here are two points, purple at (2,2) and green at (3,3). We can take two points away from each other to derive a vector. Let's create a vector to describe the magnitude and direction of purple from green: |d| = purple - green |d| = (purple.x, purple.y) - (green.x, green.y) |d| = (2, 2) - (3, 3) |d| = <-1,-1> Let's derive the magnitude of the vector via Pythagoras to get a Euclidean measurement: euc_magnitude = sqrt((x*x)+(y*y)) euc_magnitude = sqrt((-1*-1)+(-1*-1)) euc_magnitude = sqrt((1)+(1)) euc_magnitude = sqrt(2) euc_magnitude = 1.41 Now, if the answer had been 1, that would make sense to me, because 1 unit (in the direction described by the vector) from the green is bang on the purple. But it's not. It's 1.41. 1.41 units is the direction described, to me at least, makes us overshoot the purple by almost half a unit: So what do we do to the magnitude to allow us to calculate real distances on our point graph? Worth noting I'm a beginner just working my way through theory. Haven't programmed a game in my life!

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• How many vertices are needed to draw reasonably good-looking terrain?

  - by bobbaluba

  I have some pretty expensive code in my terrain vertex shader, and I am trying to figure out if it will still be fast enough. I haven't yet developed a level-of-detail system for my terrain rendering, but I can easily benchmark my code by just drawing mock triangles. My problem is, how do I know how many vertices to test with? Are there for example rendering engines that will tell me how many terrain vertices are currently on-screen? Or maybe it is possible to create a formula that will give me an estimate based on screen resolution?

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• Implementing Light Volume Front Faces

  - by cubrman

  I recently read an article about light indexed deferred rendering from here: http://code.google.com/p/lightindexed-deferredrender/ It explains its ideas in a clear way, but there was one point that I failed to understand. It in fact is one of the most interesting ones, as it explains how to implement transparency with this approach: Typically when rendering light volumes in deferred rendering, only surfaces that intersect the light volume are marked and lit. This is generally accomplished by a “shadow volume like” technique of rendering back faces – incrementing stencil where depth is greater than – then rendering front faces and only accepting when depth is less than and stencil is not zero. By only rendering front faces where depth is less than, all future lookups by fragments in the forward rendering pass will get all possible lights that could hit the fragment. Can anyone explain how exactly you need to render only front faces? Another question is why do you need the front faces at all? Why can't we simply render all the lights and store the ones that overlap at this pixel in a texture? Does this approach serves as a cut-off plane to discard lights blocked by opaque geometry?

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• How can I solve this SAT edge case?

  - by ssb

  I have an SAT implementation that basically works, and the fact that it works is what's giving me a few headaches. Basically there are some situations where using the SAT doesn't quite give me my intended result. One of these involves movement across multiple collision objects. Or to put it another way, if I have several collision boxes lined up next to each other such as to create something like a wall or a floor, movement along that surface while constantly applying force into that surface sometimes causes hangups, i.e. the player stops moving. This illustration shows what I mean: The 2 boxes on the bottom represent a floor, and the box on top/in the middle represents what my player is doing. There are several squares lined up as world obstacles to create some kind of wall, and if I move to the left across this surface while holding the down key then the issue arises. It only happens at the exact dividing point between two blocks. It only happens when moving to the left. At any rate I think I know why it happens, but I don't know how to solve it. Basically when I update my player movement I consider which directions are pressed, naturally, so if down is pressed I will add the speed to the Y component, and so on. But due to the way my SAT is implemented, when the penetration into the shape is the same from both sides it just goes with the smallest axis that it finds first, and it checks collisions against objects in the order that they were created because it goes through a foreach loop on the list of collidable objects. So this all adds up to the effect of if I'm moving to the left over a series of boxes while holding down, it will resolve me back to the right out of the first box and then up out of the box to the right of it, and this continues as long as the penetration is the same. The odd part is that this doesn't happen every time, which I am going to attribute to some oddity regarding multiplying velocity by the game time and causing some minor discrepancies between the lengths. Ultimately what this boils down to is that it will keep resolving me to the right and up, but this is technically expected behavior. All the solutions I can think of only address the symptoms of this problem and not the actual cause, such as not using many blocks to create walls or shapes, which is an option I'd like to keep open. I could also change which axis my algorithm defaults to, but that would just cause problems when going up/down along the walls. What can I do to fix this?

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• TileMapRenderer in libGDX not drawing anything

  - by Benjamin Dengler

  So I followed the tutorial on the libGDX wiki to draw Tiled maps but it doesn't seem to render anything. Here's how I setup my OrthographicCamera and load the map: camera = new OrthographicCamera(Gdx.graphics.getWidth(), Gdx.graphics.getHeight()); map = TiledLoader.createMap(Gdx.files.internal("maps/test.tmx")); atlas = new TileAtlas(map, Gdx.files.internal("maps")); tileMapRenderer = new TileMapRenderer(map, atlas, 8, 8); And here is my render function: Gdx.gl.glClearColor(0, 0, 0, 1); Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT); camera.update(); tileMapRenderer.render(camera); Also I did pack the tile map using the TiledMapPacker. I'm completely stumped... am I missing anything obvious here? EDIT: While debugging I noticed that the TileAtlas seems to be empty, which I guess shouldn't be the case, but I have no idea why it's empty.

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• Model View Control Issue: Null Pointer Initialization Question

  - by David Dimalanta

  Good morning again. This is David. Please, I need an urgent help regarding control model view where I making a code that uniquely separating into groups: An Activity Java Class to Display the Interface A View and Function Java Class for Drawing Cards and Display it on the Activity Class The problem is that the result returns a Null Pointer Exception. I have initialize for the ID for Text View and Image View. Under this class "draw_deck.java". Please help me. Here's my code for draw_deck.java: package com.bodapps.inbetween.model; import android.content.Context; import android.view.View; import android.widget.ImageView; import android.widget.TextView; import com.bodapps.inbetween.R; public class draw_deck extends View { public TextView count_label; public ImageView draw_card; private int count; public draw_deck(Context context) { super(context); // TODO Auto-generated constructor stub //I have initialized two widgets for ID. I still don't get it why I got forced closed by Null Pointer Exception thing. draw_card = (ImageView) findViewById(R.id.IV_Draw_Card); count_label = (TextView) findViewById(R.id.Text_View_Count_Card); } public void draw(int s, int c, String strSuit, String strValue, Pile pile, Context context) { //super(context); //Just printing the card drawn from pile int suit, value = 1; draw_card = (ImageView) findViewById(R.id.IV_Draw_Card); count_label = (TextView) findViewById(R.id.Text_View_Count_Card); Card card; if(!pile.isEmpty()) //Setting it to IF statement displays the card one by one. { card = pile.drawFromPile(); //Need to check first if card is null. if (card != null) { //draws an extra if (card != null) { //Get suit of card to print out. suit = card.getSuit(); switch (suit) { case CardInfo.DIAMOND: strSuit = "DIAMOND"; s=0; break; case CardInfo.HEART: strSuit = "HEART"; s=1; break; case CardInfo.SPADE: strSuit = "SPADE"; s=2; break; case CardInfo.CLUB: strSuit = "CLUB"; s=3; break; } //Get value of card to print out. value = card.getValue(); switch (value) { case CardInfo.ACE: strValue = "ACE"; c=0; break; case CardInfo.TWO: c=1; break; case CardInfo.THREE: strValue = "THREE"; c=2; break; case CardInfo.FOUR: strValue = "FOUR"; c=3; break; case CardInfo.FIVE: strValue = "FIVE"; c=4; break; case CardInfo.SIX: strValue = "SIX"; c=4; break; case CardInfo.SEVEN: strValue = "SEVEN"; c=4; break; case CardInfo.EIGHT: strValue = "EIGHT"; c=4; break; case CardInfo.NINE: strValue = "NINE"; c=4; break; case CardInfo.TEN: strValue = "TEN"; c=4; break; case CardInfo.JACK: strValue = "JACK"; c=4; break; case CardInfo.QUEEN: strValue = "QUEEN"; c=4; break; case CardInfo.KING: strValue = "KING"; c=4; break; } } } }// //Below two lines of code, this is where issued the Null Pointer Exception. draw_card.setImageResource(deck[s][c]); count_label.setText(new StringBuilder(strValue).append(" of ").append(strSuit).append(String.valueOf(" " + count++)).toString()); } //Choice of Suits in a Deck public Integer[][] deck = { //Array Group 1 is [0][0] (No. of Cards: 4 - DIAMOND) { R.drawable.card_dummy_1, R.drawable.card_dummy_2, R.drawable.card_dummy_4, R.drawable.card_dummy_5, R.drawable.card_dummy_3 }, //Array Group 2 is [1][0] (No. of Cards: 4 - HEART) { R.drawable.card_dummy_1, R.drawable.card_dummy_2, R.drawable.card_dummy_4, R.drawable.card_dummy_5, R.drawable.card_dummy_3 }, //Array Group 3 is [2][0] (No. of Cards: 4 - SPADE) { R.drawable.card_dummy_1, R.drawable.card_dummy_2, R.drawable.card_dummy_4, R.drawable.card_dummy_5, R.drawable.card_dummy_3 }, //Array Group 4 is [3][0] (No. of Cards: 4 - CLUB) { R.drawable.card_dummy_1, R.drawable.card_dummy_2, R.drawable.card_dummy_4, R.drawable.card_dummy_5, R.drawable.card_dummy_3 }, }; } And this one of the activity class, Player_Mode_2.java: package com.bodapps.inbetween; import java.util.Random; import android.app.Activity; import android.app.Dialog; import android.content.Context; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.ImageView; import android.widget.TextView; import android.widget.Toast; import com.bodapps.inbetween.model.Card; import com.bodapps.inbetween.model.Pile; import com.bodapps.inbetween.model.draw_deck; /* * * Public class for Two-Player mode. * */ public class Player_Mode_2 extends Activity { //Image Views private ImageView draw_card; private ImageView player_1; private ImageView player_2; private ImageView icon; //Buttons private Button set_deck; //Edit Texts private EditText enter_no_of_decks; //text Views private TextView count_label; //Integer Data Types private int no_of_cards, count; private int card_multiplier; //Contexts final Context context = this; //Pile Model public Pile pile; //Card Model public Card card; //create View @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.play_2_player_mode); //-----[ Search for Views ]----- //Initialize for Image View draw_card = (ImageView) findViewById(R.id.IV_Draw_Card); player_1 = (ImageView) findViewById(R.id.IV_Player_1_Card); player_2 = (ImageView) findViewById(R.id.IV_Player_2_Card); //Initialize for Text view or Label count_label = (TextView) findViewById(R.id.Text_View_Count_Card); //-----[ Adding Values ]----- //Integer Values count = 0; no_of_cards = 0; //-----[ Adding Dialog ]----- //Initializing Dialog final Dialog deck_dialog = new Dialog(context); deck_dialog.setContentView(R.layout.dialog); deck_dialog.setTitle("Deck Dialog"); //-----[ Initializing Views for Dialog's Contents ]----- //Initialize for Edit Text enter_no_of_decks = (EditText) deck_dialog.findViewById(R.id.Edit_Text_Set_Number_of_Decks); //Initialize for Button set_deck = (Button) deck_dialog.findViewById(R.id.Button_Deck); //-----[ Setting onClickListener() ]----- //Set Event Listener for Image view draw_card.setOnClickListener(new Draw_Card_Model()); //Set Event Listener for Setting the Deck set_deck.setOnClickListener(new OnClickListener() { public void onClick(View v) { if(card_multiplier <= 8) { //Use "Integer.parseInt()" method to instantly convert from String to int value. card_multiplier = Integer.parseInt(enter_no_of_decks.getText().toString()); //Shuffling cards... pile = new Pile(card_multiplier); //Multiply no. of decks //Dismiss or close the dialog. deck_dialog.dismiss(); } else { Toast.makeText(getApplicationContext(), "Please choose a number from 1 to 8.", Toast.LENGTH_SHORT).show(); } } }); //Show dialog. deck_dialog.show(); } //Shuffling the Array public void Shuffle_Cards(Integer[][] Shuffle_Deck) { Random random = new Random(); for(int i = Shuffle_Deck[no_of_cards].length - 1; i >=0; i--) { int Index = random.nextInt(i + 1); //Simple Swapping Integer swap = Shuffle_Deck[card_multiplier-1][Index]; Shuffle_Deck[card_multiplier-1][Index] = Shuffle_Deck[card_multiplier-1][i]; Shuffle_Deck[card_multiplier-1][i] = swap; } } //Private Class for Random Card Draw private class Draw_Card_Model implements OnClickListener { public void onClick(View v) { //Just printing the card drawn from pile int suit = 0, value = 0; String strSuit = "", strValue = ""; draw_deck draw = new draw_deck(context); //This line is where issued the Null Pointer Exception. if (count == card_multiplier*52) { // A message shows up when all cards are draw out. Toast.makeText(getApplicationContext(), "All cards have been used up.", Toast.LENGTH_SHORT).show(); draw_card.setEnabled(false); } else { draw.draw(suit, value, strSuit, strValue, pile, context); count_label.setText(count); //This is where I got force closed error, although "int count" have initialized the number. This was supposed to accept in the setText() method. count++; } } } } Take note that the issues on Null Pointer Exception is the Image View and the Edit Text. I got to test it. Thanks. If you have any info about my question, let me know it frankly.

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• DirectWrite Producing Strange Artifacts?

  - by smoth190

  I've written the basis to my UI system around Direct2D. I like it because it's fast and easy to use (even if I had to do some messy work to get it to work with DirectX11). However, I notice when using DirectWrite I'm getting strange problems with my text. As you can see, the e is a little screwwed up, and it overall looks a little bumpy. This only happens with certain fonts in certain sizes, and with certain arrangements of letters. This particular example is Verdana in size 16.0 font. Can I fix this? It's pretty annoying to change all my words and fonts because of this problem.

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• Creating a newspaper that effects the game's economy?

  - by zardon

  I am writing a game in Objective C/cocos2d where a newspaper is a central part of what controls or rather effects the game's world economy as well as what a city might do (such as increase X, reduce Y) The newspaper is a bit like a "Chance card" in Monopoly, it has an effect on something. My question is, what is the best way to do write a newspaper that has both a random and specific effect within the game. Would the best strategy be to write out all the things a newspaper can affect, a PLIST of headlines (with placeholders). I think Tiny Tower uses a PLIST of events and it randomly picks an event, but I'm not sure how it actually parses it because certain events do different things. But then how do I parse all the scenarios that a newspaper can deliver? A big switch statement seems very long and complicated to do. I am wondering if there is a simpler way to handle this kind of thing. Related to this is that there might be no news that day and I'm not sure what the newspaper should display, should it just display the last headline? So, in summary. 1) A newspaper generates a headline, it affects different things, such as the world economy, prices, how city reacts 2) I need the newspaper to generate headlines (although there may be days when there are no headlines at all), but I am not sure how to parse it without using a big-ass switch statement. Thanks in advance.

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• Component-wise GLSL vector branching

  - by Gustavo Maciel

  I'm aware that it usually is a BAD idea to operate separately on GLSL vec's components separately. For example: //use instrinsic functions, they do the calculation on 4 components at a time. float dot = v1.x*v2.x + v1.y * v2.y + v1.z * v2.z; //NEVER float dot = dot(v1, v2); //YES //Multiply one by one is not good too, since the ALU can do the 4 components at a time too. vec3 mul = vec3(v1.x * v2.x, v1.y * v2.y, v1.z * v2.z); //NEVER vec3 mul = v1 * v2; I've been struggling thinking, are there equivalent operations for branching? For example: vec4 Overlay(vec4 v1, vec4 v2, vec4 opacity) { bvec4 less = lessThan(v1, vec4(0.5)); vec4 blend; for(int i = 0; i < 4; ++i) { if(less[i]) blend[i] = 2.0 * v1[i]*v2[i]; else blend[i] = 1.0 - 2.0 * (1.0 - v1[i])*(1.0 - v2[i]); } return v1 + (blend-v1)*opacity; } This is a Overlay operator that works component wise. I'm not sure if this is the best way to do it, since I'm afraid these for and if can be a bottleneck later. Tl;dr, Can I branch component wise? If yes, how can I optimize that Overlay function with it?

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• What is the best way to "carve" a terrain created from a heightmap?

  - by tigrou

  I have a 3d landscape created from a heightmap. I'd like to "carve" some holes in that terrain. That will allow me to create bridges, caverns and tunnels inside it. That operation will be done in the game editor so it doesn't need to be realtime. In the end, rendering is done using traditional polygons. What would be the best/easiest way to do that ? I already think about several solutions : Solution 1 1) Create voxels from the heightmap (very easy). In other words, fill a 3D array like this : voxels[32][32][32] from the heightmap values. 2) Carve holes in the voxels as i want (easy too). 3) Convert voxels to polygons using some iso-surface extraction technique (like marching cubes). 4) Reduce (decimate) polygons created in 3). This technique seems to be the most promising for giving good results (untested). However the problem with marching cubes is that they tends to produce lots of polygons thus reducing them is mandatory. Implementing 4) also seems not trivial, i have read several papers on the web and it seems pretty complex. I was also unable to find an example, code snippet or something to start writing an algorithm for triangle mesh decimation. Maybe there is a special decimation algorithm (simpler) for meshes created from marching cubes ? Solution 2 1) Create some triangle mesh from the heighmap (easy). 2) Apply severals 3D boolean operation (eg: subtraction with a sphere) to carve the mesh. 3) apply some procedure to reduce polygons (optional). Operation 2) seems to be very complex and to be honest i have no idea how to do that. Also applying many boolean operation seems to be slow and will maybe degrade the triangle mesh every time a boolean operation is applied.

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• Narrow-phase collision detection algorithms

  - by Marian Ivanov

  There are three phases of collision detection. Broadphase: It loops between all objecs that can interact, false positives are allowed, if it would speed up the loop. Narrowphase: Determines whether they collide, and sometimes, how, no false positives Resolution: Resolves the collision. The question I'm asking is about the narrowphase. There are multiple algorithms, differing in complexity and accuracy. Hitbox intersection: This is an a-posteriori algorithm, that has the lowest complexity, but also isn't too accurate, Color intersection: Hitbox intersection for each pixel, a-posteriori, pixel-perfect, not accuratee in regards to time, higher complexity Separating axis theorem: This is used more often, accurate for triangles, however, a-posteriori, as it can't find the edge, when taking last frame in account, it's more stable Linear raycasting: A-priori algorithm, useful for semi-realistic-looking physics, finds the intersection point, even more accurate than SAT, but with more complexity Spline interpolation: A-priori, even more accurate than linear rays, even more coplexity. There are probably many more that I've forgot about. The question is, in when is it better to use SAT, when rays, when splines, and whether there is anything better.

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• What's a good way to programmatically manage a cloneable entity?

  - by bobobobo

  Say you have missiles or rockets that a player can fire. What's a good way to programmatically manage the cloning of a base rocket, for example? I can think of 2 ways to do it: Player has a currently selected weapon (which is an int) When player shoots, the selectedWeapon member is looked at, and the correct instance of rocket is created (with some base parameters) Or Player has a currently selected weapon (which is a pointer, to a "base instance" of the rocket object) When player shoots, the base instance rocket is cloned, transformed, and shot into the game world

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• Friction not working for Vehicle in BulletPhysics

  - by Manmohan Bishnoi

  I am creating a vehicle using bullet-physics engine (v 2.82). I created a ground ( btBoxShape ), a box and a vehicle (following the demo). But friction between ground and vehicle wheels seems not working. As soon as the vehicle is placed in 3d world, it starts moving forward. START : Steering works for the vehicle, but engineForce and brakingForce does not work (i.e. I cannot speed-up or stop the vehicle) : I create physics world like this : void initPhysics() { broadphase = new btDbvtBroadphase(); collisionConfiguration = new btDefaultCollisionConfiguration(); dispatcher = new btCollisionDispatcher(collisionConfiguration); solver = new btSequentialImpulseConstraintSolver(); dynamicsWorld = new btDiscreteDynamicsWorld(dispatcher, broadphase, solver, collisionConfiguration); dynamicsWorld->setGravity(btVector3(0, -9.81, 0)); // Debug Drawer bulletDebugugger.setDebugMode(btIDebugDraw::DBG_DrawWireframe); dynamicsWorld->setDebugDrawer(&bulletDebugugger); //groundShape = new btStaticPlaneShape(btVector3(0, 1, 0), 1); groundShape = new btBoxShape(btVector3(50, 3, 50)); fallShape = new btBoxShape(btVector3(1, 1, 1)); // Orientation and Position of Ground groundMotionState = new btDefaultMotionState(btTransform(btQuaternion(0, 0, 0, 1), btVector3(0, -3, 0))); btRigidBody::btRigidBodyConstructionInfo groundRigidBodyCI(0, groundMotionState, groundShape, btVector3(0, 0, 0)); groundRigidBody = new btRigidBody(groundRigidBodyCI); dynamicsWorld->addRigidBody(groundRigidBody); /////////////////////////////////////////////////////////////////////// // Vehicle Setup /////////////////////////////////////////////////////////////////////// vehicleChassisShape = new btBoxShape(btVector3(1.f, 0.5f, 2.f)); vehicleBody = new btCompoundShape(); localTrans.setIdentity(); localTrans.setOrigin(btVector3(0, 1, 0)); vehicleBody->addChildShape(localTrans, vehicleChassisShape); localTrans.setOrigin(btVector3(3, 0.f, 0)); vehicleMotionState = new btDefaultMotionState(localTrans); //vehicleMotionState = new btDefaultMotionState(btTransform(btQuaternion(0, 0, 0, 1), btVector3(3, 0, 0))); btVector3 vehicleInertia(0, 0, 0); vehicleBody->calculateLocalInertia(vehicleMass, vehicleInertia); btRigidBody::btRigidBodyConstructionInfo vehicleRigidBodyCI(vehicleMass, vehicleMotionState, vehicleBody, vehicleInertia); vehicleRigidBody = new btRigidBody(vehicleRigidBodyCI); dynamicsWorld->addRigidBody(vehicleRigidBody); wheelShape = new btCylinderShapeX(btVector3(wheelWidth, wheelRadius, wheelRadius)); { vehicleRayCaster = new btDefaultVehicleRaycaster(dynamicsWorld); vehicle = new btRaycastVehicle(vehicleTuning, vehicleRigidBody, vehicleRayCaster); // never deactivate vehicle vehicleRigidBody->setActivationState(DISABLE_DEACTIVATION); dynamicsWorld->addVehicle(vehicle); float connectionHeight = 1.2f; bool isFrontWheel = true; vehicle->setCoordinateSystem(rightIndex, upIndex, forwardIndex); // 0, 1, 2 // add wheels // front left btVector3 connectionPointCS0(CUBE_HALF_EXTENT-(0.3*wheelWidth), connectionHeight, 2*CUBE_HALF_EXTENT-wheelRadius); vehicle->addWheel(connectionPointCS0, wheelDirectionCS0, wheelAxleCS, suspensionRestLength, wheelRadius, vehicleTuning, isFrontWheel); // front right connectionPointCS0 = btVector3(-CUBE_HALF_EXTENT+(0.3*wheelWidth), connectionHeight, 2*CUBE_HALF_EXTENT-wheelRadius); vehicle->addWheel(connectionPointCS0, wheelDirectionCS0, wheelAxleCS, suspensionRestLength, wheelRadius, vehicleTuning, isFrontWheel); isFrontWheel = false; // rear right connectionPointCS0 = btVector3(-CUBE_HALF_EXTENT+(0.3*wheelWidth), connectionHeight, -2*CUBE_HALF_EXTENT+wheelRadius); vehicle->addWheel(connectionPointCS0, wheelDirectionCS0, wheelAxleCS, suspensionRestLength, wheelRadius, vehicleTuning, isFrontWheel); // rear left connectionPointCS0 = btVector3(CUBE_HALF_EXTENT-(0.3*wheelWidth), connectionHeight, -2*CUBE_HALF_EXTENT+wheelRadius); vehicle->addWheel(connectionPointCS0, wheelDirectionCS0, wheelAxleCS, suspensionRestLength, wheelRadius, vehicleTuning, isFrontWheel); for (int i = 0; i < vehicle->getNumWheels(); i++) { btWheelInfo& wheel = vehicle->getWheelInfo(i); wheel.m_suspensionStiffness = suspensionStiffness; wheel.m_wheelsDampingRelaxation = suspensionDamping; wheel.m_wheelsDampingCompression = suspensionCompression; wheel.m_frictionSlip = wheelFriction; wheel.m_rollInfluence = rollInfluence; } } /////////////////////////////////////////////////////////////////////// // Orientation and Position of Falling body fallMotionState = new btDefaultMotionState(btTransform(btQuaternion(0, 0, 0, 1), btVector3(-1, 5, 0))); btScalar mass = 1; btVector3 fallInertia(0, 0, 0); fallShape->calculateLocalInertia(mass, fallInertia); btRigidBody::btRigidBodyConstructionInfo fallRigidBodyCI(mass, fallMotionState, fallShape, fallInertia); fallRigidBody = new btRigidBody(fallRigidBodyCI); dynamicsWorld->addRigidBody(fallRigidBody); } I step physics world like this : // does not work vehicle->applyEngineForce(maxEngineForce, WHEEL_REARLEFT); vehicle->applyEngineForce(maxEngineForce, WHEEL_REARRIGHT); // these also do not work vehicle->setBrake(gBreakingForce, WHEEL_REARLEFT); vehicle->setBrake(gBreakingForce, WHEEL_REARRIGHT); // this works vehicle->setSteeringValue(gVehicleSteering, WHEEL_FRONTLEFT); vehicle->setSteeringValue(gVehicleSteering, WHEEL_FRONTRIGHT); dynamicsWorld->stepSimulation(1 / 60.0f, 10); However If I apply brakingForce to all 4 wheels (i.e. including WHEEL_FRONTLEFT and WHEEL_FRONTRIGHT), then my vehicle stops, but keeps sliding/moving forward very very slowly. How do I fix this ?

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• Javascript A* path finding ENEMY MOVEMENT in 3D environment

  - by faiz

  iam trying to implement pathfinding algorithm using PATHFINDING.JS in 3D world using webgl. iam have made a matrix of 200x200. and placed my enemy(swat) in it .iam confused in implmenting the path. i have tried implementing the path by compparing the value of each array value with swat's position . it works ! but ** THE ENEMY KEEPS GOING FROM THE UNWALKABLE AREA OF MY MATRIX....like the enemy should not move from 119,100(x=119,z=100) but its moving from that co-ordinate too ..... can any one help me out in this regard .. *prob facing :* enemy (swat character keeps moving from the wall /unwalkable area) wanted solution : enemy does not move from the unwalkable path.. ** function draw() { grid = new PF.Grid(200, 200); grid.setWalkableAt( 119,100, false); grid.setWalkableAt( 107,100, false); grid.setWalkableAt( 103,104, false); grid.setWalkableAt( 103,100, false); grid.setWalkableAt( 135,100, false); grid.setWalkableAt( 103,120, false); grid.setWalkableAt( 103,112, false); grid.setWalkableAt( 127,100, false); grid.setWalkableAt( 123,100, false); grid.setWalkableAt( 139,100, false); grid.setWalkableAt( 103,124, false); grid.setWalkableAt( 103,128, false); grid.setWalkableAt( 115,100, false); grid.setWalkableAt( 131,100, false); grid.setWalkableAt( 103,116, false); grid.setWalkableAt( 103,108, false); grid.setWalkableAt( 111,100, false); grid.setWalkableAt( 103,132, false); finder = new PF.AStarFinder(); f1=Math.abs(first_person_controller.position.x); f2=Math.abs(first_person_controller.position.z); ff1=Math.round(f1); ff2=Math.round(f2); s1=Math.abs(swat.position.x); s2=Math.abs(swat.position.z); ss1=Math.round(s1); ss2=Math.round(s1); path = finder.findPath(ss1,ss2,ff1,ff2, grid); size=path.length-1; Ai(); } function Ai(){ if (i<size) { if (swat.position.x >= path[i][0]) { swat.position.x -= 0.3; if(Math.floor(swat.position.x) == path[i][0]) { i=i+1; } } else if(swat.position.x <= path[i][0]) { swat.position.x += 0.3; if(Math.floor(swat.position.x) == path[i][0]) { i=i+1; } } } if (j<size) { if((Math.abs(swat.position.z)) >= path[j][1]) { swat.position.z -= 0.3; if(Math.floor(Math.abs(swat.position.z)) == path[j][1]) { j=j+1; } } else if((Math.abs(swat.position.z)) <= path[j][1]) { swat.position.z += 0.3; if(Math.floor(Math.abs(swat.position.z)) == path[j][1]) { j=j+1; } } } }

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• Artifacts when using SamplerState.LinearClamp in SpriteBatch

  - by Raymond Holmboe

  I'm using XNA 4.0 and VS2010 Express for Windows Phone and Windows Phone SDK 7.1. This is a platform game and I have a map made up of 16x16 textures that is drawn dynamically, tile by tile. When using SpriteBatch to draw my map with LinearClamp, I get artifacts that looks like blurry thin lines. They become visible when the camera moves from one pixel to another and when the camera is still, the artifacts disappear. Here's a small sample of what I mean: Here's how I draw with the spritebatch: SBWorld.Begin(SpriteSortMode.Deferred, BlendState.NonPremultiplied, SamplerState.LinearClamp, DepthStencilState.Default, RasterizerState.CullNone, null, camera.View); When using SamplerState.PointClamp the game just plays horribly (IMHO), so I cannot use that. Why do these lines appear and how do I get rid of those?

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• What's the proper way to calculate probability for a card game?

  - by Milan Babuškov

  I'm creating AI for a card game, and I run into problem calculating the probability of passing/failing the hand when AI needs to start the hand. Cards are A, K, Q, J, 10, 9, 8, 7 (with A being the strongest) and AI needs to play to not take the hand. Assuming there are 4 cards of the suit left in the game and one is in AI's hand, I need to calculate probability that one of the other players would take the hand. Here's an example: AI player has: J Other 2 players have: A, K, 7 If a single opponent has AK7 then AI would lose. However, if one of the players has A or K without 7, AI would survive. Now, looking at possible distribution, I have: P1 P2 AI --- --- --- AK7 loses AK 7 survives A7 K survives K7 A survives A 7K survives K 7A survives 7 KA survives AK7 loses Looking at this, it seems that there is 75% chance of survival. However, I skipped the permutations that mirror the ones from above. It should be the same, but somehow when I write them all down, it seems that chance is only 50%: P1 P2 AI --- --- --- AK7 loses A7K loses K7A loses KA7 loses 7AK loses 7KA loses AK 7 survives A7 K survives K7 A survives KA 7 survives 7A K survives 7K A survives A K7 survives A 7K survives K 7A survives K A7 survives 7 AK survives 7 KA survives AK7 loses A7K loses K7A loses KA7 loses 7AK loses 7KA loses 12 loses, 12 survivals = 50% chance. Obviously, it should be the same (shouldn't it?) and I'm missing something in one of the ways to calculate. Which one is correct?

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• Need ideas for an algorithm to draw irregular blotchy shapes

  - by Yttermayn

  I'm looking to draw irregular shapes on an x,y grid, and I'd like to come up with a simple, fast method if possible. My only idea so far is to draw a bunch of circles of random sizes very near each other, but at a random distance apart from a more or less central coordinate, then fill in any blank spaces. I realize this is a clunky, inelegant method, hopefully it will give you a rough idea of the kinds of rounded, random blotchy shapesI'm shooting for. Please suggest methods to accomplish this, I'm not so much interested in code. I can noodle that part out myself. Thanks!

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• Developing an ELO like point system for a multiplayer gaming site

  - by Alejandro Piad

  I'm currently working on a gaming site where users will submit virtual players for different games, like Chess, Nash, Backgammon, Go, etc. The idea is that users don't compete themselves, but through their virtual players. There will be leagues, tournaments, and other competition formats. The question is which would be a good rating system for users in this environment. Take into account that every user may have many different virtual players playing in many different games. As a general guideline I would like to guarantee the following properties: Users who have a lot of mediocre players should not score higher than users with a few very good players. A user with a high rating should not be penalized if he adds a new bad player, until he has had enough time to improve his player. Users who don't play often should not score higher than users who play every day. Thanks in advance.

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• Hero/Character sprite size in comparison to tile size?

  - by Kid

  So I'm making this simple platformer where the Hero is 16x16 in size, but also, the tile size is 16x16. Which sounds fine right? But my game window/world is 800x416, which makes the Hero is really really tiny in comparison. This really surprised me, but given Ive never made a platformer before it is also a new discovery. Is there a rule set for scale in platformer games? I'd like to have my game window remain the size it is (800x416), cause the game involves large levels. But how big should my hero be? I hope I was clear with the question, and I appreciate any insight. Thanks

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• C# creating a simple snake game

  - by Guy David

  I was thinking about creating a snake game with C#, so I ran ideas in my head, and some problems came up. How can I track and output in the correct location the blocks that run after the snake's head? If the snake is built of five blocks, and the user starts going in a circle, how can I print the snake body in the right location? Also, how can I create an action that will run on the background, which will move the snake forward, no matter what the user does? What structure should my code have? (code design structure) This should be a console application, since it's the only framework I am familiar with. I am not looking for finished code, since I want to really understand how it should work.

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• 3D Ball Physics Theory: collision response on ground and against walls?

  - by David

  I'm really struggling to get a strong grasp on how I should be handling collision response in a game engine I'm building around a 3D ball physics concept. Think Monkey Ball as an example of the type of gameplay. I am currently using sphere-to-sphere broad phase, then AABB to OBB testing (the final test I am using right now is one that checks if one of the 8 OBB points crosses the planes of the object it is testing against). This seems to work pretty well, and I am getting back: Plane that object is colliding against (with a point on the plane, the plane's normal, and the exact point of intersection. I've tried what feels like dozens of different high-level strategies for handling these collisions, without any real success. I think my biggest problem is understanding how to handle collisions against walls in the x-y axes (left/right, front/back), which I want to have elasticity, and the ground (z-axis) where I want an elastic reaction if the ball drops down, but then for it to eventually normalize and be kept "on the ground" (not go into the ground, but also not continue bouncing). Without kluging something together, I'm positive there is a good way to handle this, my theories just aren't getting me all the way there. For physics modeling and movement, I am trying to use a Euler based setup with each object maintaining a position (and destination position prior to collision detection), a velocity (which is added onto the position to determine the destination position), and an acceleration (which I use to store any player input being put on the ball, as well as gravity in the z coord). Starting from when I detect a collision, what is a good way to approach the response to get the expected behavior in all cases? Thanks in advance to anyone taking the time to assist... I am grateful for any pointers, and happy to post any additional info or code if it is useful. UPDATE Based on Steve H's and eBusiness' responses below, I have adapted my collision response to what makes a lot more sense now. It was close to right before, but I didn't have all the right pieces together at the right time! I have one problem left to solve, and that is what is causing the floor collision to hit every frame. Here's the collision response code I have now for the ball, then I'll describe the last bit I'm still struggling to understand. // if we are moving in the direction of the plane (against the normal)... if (m_velocity.dot(intersection.plane.normal) <= 0.0f) { float dampeningForce = 1.8f; // eventually create this value based on mass and acceleration // Calculate the projection velocity PVRTVec3 actingVelocity = m_velocity.project(intersection.plane.normal); m_velocity -= actingVelocity * dampeningForce; } // Clamp z-velocity to zero if we are within a certain threshold // -- NOTE: this was an experimental idea I had to solve the "jitter" bug I'll describe below float diff = 0.2f - abs(m_velocity.z); if (diff > 0.0f && diff <= 0.2f) { m_velocity.z = 0.0f; } // Take this object to its new destination position based on... // -- our pre-collision position + vector to the collision point + our new velocity after collision * time // -- remaining after the collision to finish the movement m_destPosition = m_position + intersection.diff + (m_velocity * intersection.tRemaining * GAMESTATE->dt); The above snippet is run after a collision is detected on the ball (collider) with a collidee (floor in this case). With a dampening force of 1.8f, the ball's reflected "upward" velocity will eventually be overcome by gravity, so the ball will essentially be stuck on the floor. THIS is the problem I have now... the collision code is running every frame (since the ball's z-velocity is constantly pushing it a collision with the floor below it). The ball is not technically stuck, I can move it around still, but the movement is really goofy because the velocity and position keep getting affected adversely by the above snippet. I was experimenting with an idea to clamp the z-velocity to zero if it was "close to zero", but this didn't do what I think... probably because the very next frame the ball gets a new gravity acceleration applied to its velocity regardless (which I think is good, right?). Collisions with walls are as they used to be and work very well. It's just this last bit of "stickiness" to deal with. The camera is constantly jittering up and down by extremely small fractions too when the ball is "at rest". I'll keep playing with it... I like puzzles like this, especially when I think I'm close. Any final ideas on what I could be doing wrong here? UPDATE 2 Good news - I discovered I should be subtracting the intersection.diff from the m_position (position prior to collision). The intersection.diff is my calculation of the difference in the vector of position to destPosition from the intersection point to the position. In this case, adding it was causing my ball to always go "up" just a little bit, causing the jitter. By subtracting it, and moving that clamper for the velocity.z when close to zero to being above the dot product (and changing the test from <= 0 to < 0), I now have the following: // Clamp z-velocity to zero if we are within a certain threshold float diff = 0.2f - abs(m_velocity.z); if (diff > 0.0f && diff <= 0.2f) { m_velocity.z = 0.0f; } // if we are moving in the direction of the plane (against the normal)... float dotprod = m_velocity.dot(intersection.plane.normal); if (dotprod < 0.0f) { float dampeningForce = 1.8f; // eventually create this value based on mass and acceleration? // Calculate the projection velocity PVRTVec3 actingVelocity = m_velocity.project(intersection.plane.normal); m_velocity -= actingVelocity * dampeningForce; } // Take this object to its new destination position based on... // -- our pre-collision position + vector to the collision point + our new velocity after collision * time // -- remaining after the collision to finish the movement m_destPosition = m_position - intersection.diff + (m_velocity * intersection.tRemaining * GAMESTATE->dt); UpdateWorldMatrix(m_destWorldMatrix, m_destOBB, m_destPosition, false); This is MUCH better. No jitter, and the ball now "rests" at the floor, while still bouncing off the floor and walls. The ONLY thing left is that the ball is now virtually "stuck". He can move but at a much slower rate, likely because the else of my dot product test is only letting the ball move at a rate multiplied against the tRemaining... I think this is a better solution than I had previously, but still somehow not the right idea. BTW, I'm trying to journal my progress through this problem for anyone else with a similar situation - hopefully it will serve as some help, as many similar posts have for me over the years.

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• How to design good & continuous tiles

  - by Mikalichov

  I have trouble designing tiles so that when assembled, they don't look like tiles, but look like an homogeneous thing. For example on the image below: even though the main part of the grass is only one tile, you don't "see" the grid; you know where it is if you look a bit carefully, but it is not obvious. Whereas when I design tiles, you can only see "oh, jeez, 64 times the same tile". A bit like on that image: (taken from a gamedev.stackexchange question, sorry; no critic about the game, but it proves my point, and actually has better tile design that what I manage) I think the main problem is that I design them so they are independent, there is no junction between two tiles if put closed to each other. I think having the tiles more "continuous" would have a smoother effect, but can't manage to do it, it seems overly complex to me. I think it is probably simpler than I think once you know how to do it, but couldn't find a tutorial on that specific point. Is there a known method to design continuous / homogeneous tiles? (my terminology might be totally wrong, don't hesitate to correct me)

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• Fast pixelshader 2D raytracing

  - by heishe

  I'd like to do a simple 2D shadow calculation algorithm by rendering my environment into a texture, and then use raytracing to determine what pixels of the texture are not visible to the point light (simply handed to the shader as a vec2 position) . A simple brute force algorithm per pixel would looks like this: line_segment = line segment between current pixel of texture and light source For each pixel in the texture: { if pixel is not just empty space && pixel is on line_segment output = black else output = normal color of the pixel } This is, of course, probably not the fastest way to do it. Question is: What are faster ways to do it or what are some optimizations that can be applied to this technique?

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• convert orientation vec3 to a rotation matrix

  - by lapin

  I've got a normalized vec3 that represents an orientation. Each frame of animation, an object's orientation changes slightly, so I add a delta vector to the orientation vector and then normalize to find the new orientation. I'd like to convert the vec3 that represents an orientation into a rotation matrix that I can use to orient my object. If it helps, my object is a cone, and I'd like to rotate it about the pointy end, not from its center :) PS I know I should use quaternions because of the gimbal lock problem. If someone can explain quats too, that'd be great :)

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• How can I test if my rotated rectangle intersects a corner?

  - by Raven Dreamer

  I have a square, tile-based collision map. To check if one of my (square) entities is colliding, I get the vertices of the 4 corners, and test those 4 points against my collision map. If none of those points are intersecting, I know I'm good to move to the new position. I'd like to allow entities to rotate. I can still calculate the 4 corners of the square, but once you factor in rotation, those 4 corners alone don't seem to be enough information to determine if the entity is trying to move to a valid state. For example: In the picture below, black is unwalkable terrain, and red is the player's hitbox. The left scenario is allowed because the 4 corners of the red square are not in the black terrain. The right scenario would also be (incorrectly) allowed, because the player, cleverly turned at a 45* angle, has its corners in valid spaces, even if it is (quite literally) cutting the corner. How can I detect scenarios similar to the situation on the right?

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