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• Simple 2D Flight Physics with Box2D

  - by MarkPowell

  I'm trying to build a simple side scroller with an airplane being the player. As such, I want to build simple flight controls with simple but realistic-feeling physics. I'm making use of cocos2D and Box2D. I have a basic system working, but just can't get the physics feeling correct. I am applying force to the plane (which is a b2CircleShape) based on the user's input. So, basically, if the user pushes up, body_->ApplyForce(b2Vec2(10,30), body_->GetPosition()) is called. Similarly, for down -30 is used. This works and the plane flys along with up/down causing it to dive or climb. But it just doesn't feel right. There is no slowdown on climbs, nor speed up during dives. My simple solution is far to simple. How can I get a better feel for a plane climbing/diving? Thanks!

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• How does a segment-based rendering engine (as in Descent) work?

  - by Calmarius

  As far as I know Descent was one of the first games that featured a fully 3D environment, and it used a segment based rendering engine. Its levels are built from cubic segments (these cubes may be deformed as long as it remains convex and sides remain roughly flat). These cubes are connected by their sides. The connected sides are traversable (maybe doors or grids can be placed on these sides), while the unconnected sides are not traversable walls. So the game is played inside of this complex. Descent was software rendered and it had to be very fast, to be playable on those 10-100MHz processors of that age. Some latter levels of the game are huge and contain thousands of segments, but these levels are still rendered reasonably fast. So I think they tried to minimize the amount of cubes rendered somehow. How to choose which cubes to render for a given location? As far as I know they used a kind of portal rendering, but I couldn't find what was the technique used in this particular kind of engine. I think the fact that the levels are built from convex quadrilateral hexahedrons can be exploited.

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• Help with calculation to steer ship in 3d space

  - by Aaron Anodide

  I'm a beginner using XNA to try and make a 3D Asteroids game. I'm really close to having my space ship drive around as if it had thrusters for pitch and yaw. The problem is I can't quite figure out how to translate the rotations, for instance, when I pitch forward 45 degrees and then start to turn - in this case there should be rotation being applied to all three directions to get the "diagonal yaw" - right? I thought I had it right with the calculations below, but they cause a partly pitched forward ship to wobble instead of turn.... :( Here's current (almost working) calculations for the Rotation acceleration: float accel = .75f; // Thrust +Y / Forward if (currentKeyboardState.IsKeyDown(Keys.I)) { this.ship.AccelerationY += (float)Math.Cos(this.ship.RotationZ) * accel; this.ship.AccelerationX += (float)Math.Sin(this.ship.RotationZ) * -accel; this.ship.AccelerationZ += (float)Math.Sin(this.ship.RotationX) * accel; } // Rotation +Z / Yaw if (currentKeyboardState.IsKeyDown(Keys.J)) { this.ship.RotationAccelerationZ += (float)Math.Cos(this.ship.RotationX) * accel; this.ship.RotationAccelerationY += (float)Math.Sin(this.ship.RotationX) * accel; this.ship.RotationAccelerationX += (float)Math.Sin(this.ship.RotationY) * accel; } // Rotation -Z / Yaw if (currentKeyboardState.IsKeyDown(Keys.K)) { this.ship.RotationAccelerationZ += (float)Math.Cos(this.ship.RotationX) * -accel; this.ship.RotationAccelerationY += (float)Math.Sin(this.ship.RotationX) * -accel; this.ship.RotationAccelerationX += (float)Math.Sin(this.ship.RotationY) * -accel; } // Rotation +X / Pitch if (currentKeyboardState.IsKeyDown(Keys.F)) { this.ship.RotationAccelerationX += accel; } // Rotation -X / Pitch if (currentKeyboardState.IsKeyDown(Keys.D)) { this.ship.RotationAccelerationX -= accel; } I'm combining that with drawing code that does a rotation to the model: public void Draw(Matrix world, Matrix view, Matrix projection, TimeSpan elsapsedTime) { float seconds = (float)elsapsedTime.TotalSeconds; // update velocity based on acceleration this.VelocityX += this.AccelerationX * seconds; this.VelocityY += this.AccelerationY * seconds; this.VelocityZ += this.AccelerationZ * seconds; // update position based on velocity this.PositionX += this.VelocityX * seconds; this.PositionY += this.VelocityY * seconds; this.PositionZ += this.VelocityZ * seconds; // update rotational velocity based on rotational acceleration this.RotationVelocityX += this.RotationAccelerationX * seconds; this.RotationVelocityY += this.RotationAccelerationY * seconds; this.RotationVelocityZ += this.RotationAccelerationZ * seconds; // update rotation based on rotational velocity this.RotationX += this.RotationVelocityX * seconds; this.RotationY += this.RotationVelocityY * seconds; this.RotationZ += this.RotationVelocityZ * seconds; Matrix translation = Matrix.CreateTranslation(PositionX, PositionY, PositionZ); Matrix rotation = Matrix.CreateRotationX(RotationX) * Matrix.CreateRotationY(RotationY) * Matrix.CreateRotationZ(RotationZ); model.Root.Transform = rotation * translation * world; model.CopyAbsoluteBoneTransformsTo(boneTransforms); foreach (ModelMesh mesh in model.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.World = boneTransforms[mesh.ParentBone.Index]; effect.View = view; effect.Projection = projection; effect.EnableDefaultLighting(); } mesh.Draw(); } }

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• Adding a short delay between bullets

  - by Sun

  I'm having some trouble simulating bullets in my 2D shooter. I want similar mechanics to Megaman, where the user can hold down the shoot button and a continues stream of bullets are fired but with a slight delay. Currently, when the user fires a bullet in my game a get an almost laser like effect. Below is a screen shot of some bullets being fired while running and jumping. In my update method I have the following: if(gc.getInput().isKeyDown(Input.KEY_SPACE) ){ bullets.add(new Bullet(player.getPos().getX() + 30,player.getPos().getY() + 17)); } Then I simply iterate through the array list increasing its x value on each update. Moreover, pressing the shoot button (Space bar) creates multiple bullets instead of just creating one even though I am adding only one new bullet to my array list. What would be the best way to solve this problem?

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• How exactly does app ranking work?

  - by qweasdzxc1

  So I've been in the app industry for around half a year and I still don't know how exactly ranking higher for your app will help increase downloads. That sounds like a question with an obvious answer but this is what's going through my mind so hear me out: Unless your app is ranked within the top 100, no one can see it in the featured categories. So even if my app jumped from 400th to 300th place, would there really even be a difference in downloads? And I'm saying 400th to 300th in ranking in my specific category. Indie developers like me don't even come close to ranking for the overall category. So far, the only usefulness of trying to get a higher rank is to get featured or something like that, but big companies have tons of money to throw on marketing...so the chances of any indie developer getting featured is rare. The only thing that I can see ranking being good for is to rank for your keywords so that when someone searches for that word, your app will hopefully appear in the top 10-25 results. Can anyone confirm my thoughts or add anything else that I might have missed out on? How exactly do users find your app if you're not in the top 100 app in your category?

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• Normalizing the direction to check if able to move

  - by spartan2417

  i have a a room with 4 walls along the x and z axis respectively. My player who is in first person (therefore the camera) should have collision detection with these walls. I'm relatively new to this so please bare with me. I believe the way to do this is to calculate the direction and distance to the wall from the camera and then normalize the directions. However i can only get this far before i dont know what to do. I think you should work out the angle and direction your facing? where _dx and _dz is the small buffer in front of the camera. float CalcDirection(float Cam_x, float Cam_z, float Wall_x, float Wall_z) { //Calculate direction and distance to obstacle. float ob_dirx = Cam_x + _dx - Wall_x; float ob_dirz = Cam_z + _dz - Wall_z; float ob_dist = sqrt(ob_dirx*ob_dirx + ob_dirz*ob_dirz); //Normalise directions float ob_norm = sqrt(ob_dirx*ob_dirx + ob_dirz*ob_dirz); ob_dirx = (ob_dirx)/ob_norm; ob_dirz = (ob_dirz)/ob_norm; can anyone explain in laymen's terms how i work out the angle?

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• Faster 2D Collision detection

  - by eShredder

  Recently I've been working on a fast-paced 2d shooter and I came across a mighty problem. Collision detection. Sure, it is working, but it is very slow. My goal is: Have lots of enemies on screen and have them to not touch each other. All of the enemies are chasing the player entity. Most of them have the same speed so sooner or later they all end up taking the same space while chasing the player. This really drops the fun factor since, for the player, it looks like you are being chased by one enemy only. To prevent them to take the same space I added a collision detection (a very basic 2D detection, the only method I know of) which is. Enemy class update method Loop through all enemies (continue; if the loop points at this object) If enemy object intersects with this object Push enemy object away from this enemy object This works fine. As long as I only have <200 enemy entities that is. When I get closer to 300-350 enemy entities my frame rate begins to drop heavily. First I thought it was bad rendering so I removed their draw call. This did not help at all so of course I realised it was the update method. The only heavy part in their update method is this each-enemy-loops-through-every-enemy part. When I get closer to 300 enemies the game does a 90000 (300x300) step itteration. My my~ I'm sure there must be another way to aproach this collision detection. Though I have no idea how. The pages I find is about how to actually do the collision between two objects or how to check collision between an object and a tile. I already know those two things. tl;dr? How do I aproach collision detection between LOTS of entities? Quick edit: If it is to any help, I'm using C# XNA.

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• Rotating wheel with touch (adding momentum and slowing down the initial rate it can be moved

  - by Lewis

  I have a wheel control in a game which is setup like so: - (void)ccTouchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [touches anyObject]; CGPoint location = [touch locationInView:[touch view]]; location = [[CCDirector sharedDirector] convertToGL:location]; if (CGRectContainsPoint(wheel.boundingBox, location)) { CGPoint firstLocation = [touch previousLocationInView:[touch view]]; CGPoint location = [touch locationInView:[touch view]]; CGPoint touchingPoint = [[CCDirector sharedDirector] convertToGL:location]; CGPoint firstTouchingPoint = [[CCDirector sharedDirector] convertToGL:firstLocation]; CGPoint firstVector = ccpSub(firstTouchingPoint, wheel.position); CGFloat firstRotateAngle = -ccpToAngle(firstVector); CGFloat previousTouch = CC_RADIANS_TO_DEGREES(firstRotateAngle); CGPoint vector = ccpSub(touchingPoint, wheel.position); CGFloat rotateAngle = -ccpToAngle(vector); CGFloat currentTouch = CC_RADIANS_TO_DEGREES(rotateAngle); wheelRotation += (currentTouch - previousTouch) * 0.6; //limit speed 0.6 } } Now once the user lets go of the wheel I want it to rotate back to where it was before but not without taking into account the momentum of the swipe the user has done. This is the bit I really can't get my head around. So if the swipe generates a lot of momentum then the wheel will carry on moving slightly in that direction until the overall force which pulls the wheel back to the starting position kicks in. Any ideas/code snippets?

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• Text on a model

  - by alecnash

  I am trying to put some text on a Model and I want it to be dynamic. Did some research and came up with drawing the text on the texture and then set it on the model. I use something like this: public static Texture2D SpriteFontTextToTexture(SpriteFont font, string text, Color backgroundColor, Color textColor) { Size = font.MeasureString(text); RenderTarget2D renderTarget = new RenderTarget2D(GraphicsDevice, (int)Size.X, (int)Size.Y); GraphicsDevice.SetRenderTarget(renderTarget); GraphicsDevice.Clear(Color.Transparent); Spritbatch.Begin(); //have to redo the ColorTexture Spritbatch.Draw(ColorTexture.Create(GraphicsDevice, 1024, 1024, backgroundColor), Vector2.Zero, Color.White); Spritbatch.DrawString(font, text, Vector2.Zero, textColor); Spritbatch.End(); GraphicsDevice.SetRenderTarget(null); return renderTarget; } When I was working with primitives and not models everything worked fine because I set the texture exactly where I wanted but with the model (RoundedRect 3D button). It now looks like that: Is there a way to have the text centered only on one side?

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• Fixing a collision detection bug in Slick2D

  - by Jesse Prescott

  My game has a bug with collision detection. If you go against the wall and tap forward/back sometimes the game thinks the speed you travelled at is 0 and the game doesn't know how to get you out of the wall. My collision detection works by getting the speed you hit the wall at and if it is positive it moves you back, if it is negative it moves you forward. It might help if you download it: https://rapidshare.com/files/1550046269/game.zip Sorry if I explained badly, it's hard to explain. float maxSpeed = 0.3f; float minSpeed = -0.2f; float acceleration = 0.002f; float deacceleration = 0.001f; float slowdownSpeed = 0.002f; float rotateSpeed = 0.08f; static float currentSpeed = 0; boolean up = false; boolean down = false; boolean noKey = false; static float rotate = 0; //Image effect system static String locationCarNormal; static String locationCarFront; static String locationCarBack; static String locationCarBoth; static boolean carFront = false; static boolean carBack = false; static String imageRef; boolean collision = false; public ComponentPlayerMovement(String id, String ScarNormal, String ScarFront, String ScarBack, String ScarBoth) { this.id = id; playerBody = new Rectangle(900/2-16, 700/2-16, 32, 32); locationCarNormal = ScarNormal; locationCarFront = ScarFront; locationCarBack = ScarBack; locationCarBoth = ScarBoth; imageRef = locationCarNormal; } @Override public void update(GameContainer gc, StateBasedGame sbg, int delta) throws SlickException { Input input = gc.getInput(); playerBody.transform(Transform.createRotateTransform(2)); float hip = currentSpeed * delta; float unstuckspeed = 0.05f * delta; if(carBack && !carFront) { imageRef = locationCarBack; ComponentImageRender.updateImage(); } else if(carFront && !carBack) { imageRef = locationCarFront; ComponentImageRender.updateImage(); } else if(carFront && carBack) { imageRef = locationCarBoth; ComponentImageRender.updateImage(); } if(input.isKeyDown(Input.KEY_RIGHT)) { rotate += rotateSpeed * delta; owner.setRotation(rotate); } if(input.isKeyDown(Input.KEY_LEFT)) { rotate -= rotateSpeed * delta; owner.setRotation(rotate); } if(input.isKeyDown(Input.KEY_UP)) { if(!collision) { up = true; noKey = false; if(currentSpeed < maxSpeed) { currentSpeed += acceleration; } MapCoordStorage.mapX += hip * Math.sin(Math.toRadians(rotate)); MapCoordStorage.mapY -= hip * Math.cos(Math.toRadians(rotate)); } else { currentSpeed = 1; } } else if(input.isKeyDown(Input.KEY_DOWN) && !collision) { down = true; noKey = false; if(currentSpeed > minSpeed) { currentSpeed -= slowdownSpeed; } MapCoordStorage.mapX += hip * Math.sin(Math.toRadians(rotate)); MapCoordStorage.mapY -= hip * Math.cos(Math.toRadians(rotate)); } else { noKey = true; if(currentSpeed > 0) { currentSpeed -= deacceleration; } else if(currentSpeed < 0) { currentSpeed += acceleration; } MapCoordStorage.mapX += hip * Math.sin(Math.toRadians(rotate)); MapCoordStorage.mapY -= hip * Math.cos(Math.toRadians(rotate)); } if(entityCollisionWith()) { collision = true; if(currentSpeed > 0 || up) { up = true; currentSpeed = 0; carFront = true; MapCoordStorage.mapX += unstuckspeed * Math.sin(Math.toRadians(rotate-180)); MapCoordStorage.mapY -= unstuckspeed * Math.cos(Math.toRadians(rotate-180)); } else if(currentSpeed < 0 || down) { down = true; currentSpeed = 0; carBack = true; MapCoordStorage.mapX += unstuckspeed * Math.sin(Math.toRadians(rotate)); MapCoordStorage.mapY -= unstuckspeed * Math.cos(Math.toRadians(rotate)); } else { currentSpeed = 0; } } else { collision = false; up = false; down = false; } if(currentSpeed >= -0.01f && currentSpeed <= 0.01f && noKey && !collision) { currentSpeed = 0; } } public static boolean entityCollisionWith() throws SlickException { for (int i = 0; i < BlockMap.entities.size(); i++) { Block entity1 = (Block) BlockMap.entities.get(i); if (playerBody.intersects(entity1.poly)) { return true; } } return false; } }

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• Auto-organized / smart inventory system?

  - by VeXe

  for the past week I've been working on an inventory system with Unity3D. At first I got help from the guys at Design3 but it wasn't too long till we split path, because I really didn't like the way they did their code, it didn't have any smell of OOP whatsoever. I took it further steps ahead - items take more than one slot, advanced placement system (items tries their best to find the best close fit), local mouse system (mouse gets trapped in active bag area), etc. Here's a demo of my work. What we would like to have in our game, is an auto-organizing feature - not auto-sort. We want this feature because our inventory's going to be in 'real-time' - not like in Resident Evil 1,2,3 etc where you would pause the game and do things in your inventory. Now imagine your self in a sticky situation surrounded by zombies, and you don't have bullets, you look around, you see that there are bullets nearby on the ground, so you go for them and try to pick them up, but they don't fit! you look at your inventory and find out that if you reorganize some of the items, it will fit! - now the player - in that situation doesn't have time to reorganize because he's surrounded with zombies and will die if he stops and organizes the inventory to make space (remember inventory in real-time, no pausing) - wouldn't it be nice for that to happen automatically? - Yes! (I believe this has been implemented in some games like Dungeon siege or something, so sure it's doable) take a look at this picture for example: Yes, so if you auto-sort the issue you will get your spaces but it's bad because: 1- Expensive: it doesn't need a whole sort operation to free those spaces, in the first picture, just slide the red item at the bottom to the very left, and you get the same spaces that you got from the auto-sort. 2- It's annoying to the player: "Who the F told you to re-order my stuff?" I'm not asking for "How to write the code" for this, I'm just asking for some guidance, where to look, what algorithms are involved? Is this something related to graphs and shortest path stuff? I hope not cuz I didn't manage to continue my college studies :/ But even if it is, just tell me and I will learn the stuff related. Notice there could be more than just one solution. So I guess the first thing I have to do is figure out if the situation is 'solvable' - if I know how to determine if a situation is solvable or not, then I can 'solve' it. I just need to know the conditions that makes it 'solvable'. And I believe there must be some algorithm/data structure for this. Here's a pic for more than one solution of trying to fit a 1x3 item: The arrows show just one of the solutions, but if you look you will find more than one. This is what I ultimately not auto-sorting but find a solution and applying it. Note that if I spend time on it I will come up with a way to solve it, but it wouldn't be the best way, it's like, holding a car wheel with your feet instead of your hands! XD Or just like trying to solve an issue that requires arrays, but you're not yet aware of their existence! So what is the right approach to this? Hope somebody helps, thanks a lot in advance :)

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• OpenGL ES multiple objects not being rendered

  - by ladiesMan217

  I am doing the following to render multiple balls move around the screen but only 1 ball is seen to appear and function. I don't know why the rest (count-1) balls are not being drawn public void onDrawFrame(GL10 gl) { // TODO Auto-generated method stub gl.glDisable(GL10.GL_DITHER); gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); gl.glMatrixMode(GL10.GL_MODELVIEW); gl.glClientActiveTexture(DRAWING_CACHE_QUALITY_HIGH); gl.glLoadIdentity(); for(int i=0;i<mParticleSystem.getParticleCount();i++){ gl.glPushMatrix(); gl.glTranslatef(mParticleSystem.getPosX(i), mParticleSystem.getPosY(i), -3.0f); gl.glScalef(0.3f, 0.3f, 0.3f); gl.glColor4f(r.nextFloat(), r.nextFloat(), r.nextFloat(), 1); gl.glEnable(GL10.GL_TEXTURE_2D); mParticleSystem.getBall(i).draw(gl); gl.glPopMatrix(); } } Here is my void draw(GL10 gl) method public void draw(GL10 gl){ gl.glEnable(GL10.GL_CULL_FACE); gl.glEnable(GL10.GL_SMOOTH); gl.glEnable(GL10.GL_DEPTH_TEST); // gl.glTranslatef(0.2f, 0.2f, -3.0f); // gl.glScalef(size, size, 1.0f); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertBuff); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glDrawArrays(GL10.GL_TRIANGLE_FAN, 0, points/2); gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); }

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• How far do I take Composition?

  - by whiterook6

  (Although I'm sure this is a common problem I really don't know what to search for. Composition is the only thing I could come up with.) I've read over and over that multiple inheritance and subclassing is really, really bad, especially for game entities. If I have three types of motions, five types of guns, and three types of armoring, I don't want to have to make 45 different classes to get all the possible combinations; I'm going to add a motion behavior, gun behavior, and armor behavior to a single generic object. That makes sense. But how far do I take this? I can have as many different types of behaviors as I can imagine: DamageBehavior, MotionBehavior, TargetableBehavior, etc. If I add a new class of behaviors then I need to update all the other classes that use them. But what happens when I have functionality that doesn't really fit into one class of behaviors? For example, my armor needs to be damageable but also updateable. And should I be able to have use more than one type of behavior on an entity at a time, such as two motion behaviors? Can anyone offer any wisdom or point me in the direction of some useful articles? Thanks!

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• Can i place a image as a map and then code a grid over the top of it?

  - by kraze

  what i'm trying to do is make a huge map, best way i found is just make a big map and save it as a image... can i code a grid over the top so i can implement tile based movement for my character? afterwards place collision tiles so they can't move to certain spots. btw this is in visual studio 2010 using XNA Anyone able to explain the process of how i would do this and if its even viable? thanks for your help

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• 3D RTS pathfinding

  - by xcrypt

  I understand the A* algorithm, but I have some trouble doing it in 3D to suit the needs of my RTS Basically, in the game I'm making, there will be agents with different sizes of OBB collision boxes. I can use steering behaviours for avoiding other agents, so I don't need complete dynamic pathfinding. However, there is a problem because different agents have different collision geometry, and structures can be placed in almost any place. This means that there might be a gap between two structures where some agents can go through and some can't. A solution I have found to this problem is to do a sweep of the collision geometry of the agent from start node of the edge the pf algorithm is currently testing, to the end node of that edge. But this is probably a bit overkill since every edge the algorithm tests would also have to create and test with a collision geometry sweep. What are some reasonable approaches to this problem? I should mention that I'd prefer not to use navmeshes, I prefer waypoints because my entire system is based on it atm.

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• FBO rendering different result between Glaxay S2 and S3

  - by BruceJones

  I'm working on a pong game and have recently set up FBO rendering so that I can apply some post-processing shaders. This proceeds as so: Bind texture A to framebuffer Draw balls Bind texture B to framebuffer Draw texture A using fade shader on fullscreen quad Bind screen to framebuffer Draw texture B using normal textured quad shader Neither texture A or B are cleared at any point, this way the balls leave trails on screen, see below for the fade shader. Fade Shader private final String fragmentShaderCode = "precision highp float;" + "uniform sampler2D u_Texture;" + "varying vec2 v_TexCoordinate;" + "vec4 color;" + "void main(void)" + "{" + " color = texture2D(u_Texture, v_TexCoordinate);" + " color.a *= 0.8;" + " gl_FragColor = color;" + "}"; This works fine with the Samsung Galaxy S3/ Note2, but cause a strange effect doesnt work on Galaxy S2 or Note1. See pictures: Galaxy S3/Note2 Galaxy S3/Note2 Galaxy S2/Note Galaxy S2/Note Can anyone explain the difference?

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• Android - Force Close - Null Pointer on Canvas?

  - by user22241

  Please bear with me. I have a very odd problem. Basically, my app so far, has 3 activities (a main splash screen, an 'options/menu' screen and the main app). If I follow the very specific steps oulined below, I get a 'null pointer exception' in the 2nd activity) and the app force closes...... Here are the steps: Start the app (a game based on Surfaceview), tap through to the third activity so the game is running, then hit the home key so the game is paused and put to the background, the activity/app is ended through DDMS in the SDK then restarted on the device (all OK so far), now if I hit the back key on the device twice in quick succession, it happens. All other sequence of events is fine, even to the point of pressing the back key, waiting for the previous activity to show, then hitting back again - all OK. Only when the back key is pressed twice in quick succession following all the above steps does the problem occur. I'm assuming that the canvas isn't ready as it's showing as 'null' when this happens, but I'm not sure why this is happening as surely it's happening when I'm trying to go back to activity 1, but the logcat shows the error in activity 2. if I stop the activity running my 'doDraw' method (which referenced the canvas), then all is OK - so I can safely assume it is the canvas causing the problem. Also, if I skip my first activity (which is a very basic full-screen button which just displays a splashscreen and waits for the user to tap the screen), and make my 2nd activity the launch activity, again, it is OK. this is the part of the code that I think is probably relevant: @Override public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) { vheight = this.getHeight(); vwidth = this.getWidth(); } @Override public void surfaceCreated(SurfaceHolder holder) { vheight = this.getHeight(); vwidth = this.getWidth(); this.viewWidth = vwidth; this.viewHeight = vheight; if (runthread==false){ if (preThread.getState()==Thread.State.TERMINATED){ preThread = new OptionsThread(thisholder, thiscontext, thishandler); } preThread.setRunning(true); preThread.start();} } @Override public void surfaceDestroyed(SurfaceHolder holder) { preThread.setRunning(false); //Stop the loop boolean retry = true; //Stop the thread while (retry) { try { preThread.join(); retry = false; } catch (InterruptedException e) { } } Thank you all for any help you can offer

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• System hangs at glReadPixel call with GL_TEXTURE_2D_ARRAY for texturing

  - by Roshan

  I am calling glReadPixel after glDrawArray call. I am rendering a geometry with 3D texture on it as a target GL_TEXTURE_2D_ARRAY. My systems hangs at glreadpixel call. When i use target as GL_TEXTURE_3D the issue does not occurs and it correctly reads the framebuffer contents. glReadPixels(0, 0, GetViewportWidth(), GetViewportHeight(), GL_RGBA, GL_UNSIGNED_BYTE, (GLvoid *)rendered_pixels); I am using SNORM textures with GL_byte data in glTeximage3D call and I am not calling glPixelStorei, is it because of this? What should be the parameter for pixelstore call?

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• Mesh with Alpha Texture doesn't blend properly

  - by faulty

  I've followed example from various place regarding setting OutputMerger's BlendState to enable alpha/transparent texture on mesh. The setup is as follows: var transParentOp = new BlendStateDescription { SourceBlend = BlendOption.SourceAlpha, DestinationBlend = BlendOption.InverseDestinationAlpha, BlendOperation = BlendOperation.Add, SourceAlphaBlend = BlendOption.Zero, DestinationAlphaBlend = BlendOption.Zero, AlphaBlendOperation = BlendOperation.Add, }; I've made up a sample that display 3 mesh A, B and C, where each overlaps one another. They are drawn sequentially, A to C. Distance from camera where A is nearest and C is furthest. So, the expected output is that A see through and saw part of B and C. B will see through and saw part of C. But what I get was none of them see through in that order, but if I move C closer to the camera, then it will be semi transparent and see through A and B. B if move closer to camera will see A but not C. Sort of reverse. So it seems that I need to draw them in reverse order where furthest from camera is drawn first then nearest to camera is drawn last. Is it suppose to be done this way, or I can actually configure the blendstate so it works no matter in which order i draw them? Thanks

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• Drawing flaming letters in 3d on OpenGL ES 2.0

  - by Chiquis

  I am a bit confused about how to achieve this. What i want is to "draw with flames". I have achieved this with textures successfully, but now my concern is about doing this with particles to achieve the flaming effect. Am I supposed to have a Path in where i should add many particle emitters along the path that will "be emitting flames"? I understand the concept for 2d, but for 3d are the particles (that are quads) always supposed to be facing the user? Edit: Something else im worried about is the performance hit that will occur by having that many particle emitters, because there can be many letters and drawings at the same time. And each of these elements will have many particle emitters.

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• How can I change this isometric engine to make it so that you could distinguish between blocks that are on different planes?

  - by l5p4ngl312

  I have been working on an isometric minecraft-esque game engine for a strategy game I plan on making. As you can see, it really needs some sort of shading. It is difficult to distinguish between separate elevations when the camera is facing away from the slope because everything is the same shade. So my question is: can I shade just a specific section of a sprite? All of those blocks are just sprites, so if I shaded the entire image, it would shade the whole block. I am using LWJGL. Are there any other approaches to take? Heres a link to a screenshot from the engine: http://i44.tinypic.com/qxqlix.jpg

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• GLSL per pixel lighting with custom light type

  - by Justin

  Ok, I am having a big problem here. I just got into GLSL yesterday, so the code will be terrible, I'm sure. Basically, I am attempting to make a light that can be passed into the fragment shader (for learning purposes). I have four input values: one for the position of the light, one for the color, one for the distance it can travel, and one for the intensity. I want to find the distance between the light and the fragment, then calculate the color from there. The code I have gives me a simply gorgeous ring of light that get's twisted and widened as the matrix is modified. I love the results, but it is not even close to what I am after. I want the light to be moved with all of the vertices, so it is always in the same place in relation to the objects. I can easily take it from there, but getting that to work seems to be impossible with my current structure. Can somebody give me a few pointers (pun not intended)? Vertex shader: attribute vec4 position; attribute vec4 color; attribute vec2 textureCoordinates; varying vec4 colorVarying; varying vec2 texturePosition; varying vec4 fposition; varying vec4 lightPosition; varying float lightDistance; varying float lightIntensity; varying vec4 lightColor; void main() { vec4 ECposition = gl_ModelViewMatrix * gl_Vertex; vec3 tnorm = normalize(vec3 (gl_NormalMatrix * gl_Normal)); fposition = ftransform(); gl_Position = fposition; gl_TexCoord[0] = gl_MultiTexCoord0; fposition = ECposition; lightPosition = vec4(0.0, 0.0, 5.0, 0.0) * gl_ModelViewMatrix * gl_Vertex; lightDistance = 5.0; lightIntensity = 1.0; lightColor = vec4(0.2, 0.2, 0.2, 1.0); } Fragment shader: varying vec4 colorVarying; varying vec2 texturePosition; varying vec4 fposition; varying vec4 lightPosition; varying float lightDistance; varying float lightIntensity; varying vec4 lightColor; uniform sampler2D texture; void main() { float l_distance = sqrt((gl_FragCoord.x * lightPosition.x) + (gl_FragCoord.y * lightPosition.y) + (gl_FragCoord.z * lightPosition.z)); float l_value = lightIntensity / (l_distance / lightDistance); vec4 l_color = vec4(l_value * lightColor.r, l_value * lightColor.g, l_value * lightColor.b, l_value * lightColor.a); vec4 color; color = texture2D(texture, gl_TexCoord[0].st); gl_FragColor = l_color * color; //gl_FragColor = fposition; }

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• Checking for collisions on a 3D heightmap

  - by Piku

  I have a 3D heightmap drawn using OpenGL (which isn't important). It's represented by a 2D array of height data. To draw this I go through the array using each point as a vertex. Three vertices are wound together to form a triangle, two triangles to make a quad. To stop the whole mesh being tiny I scale this by a certain amount called 'gridsize'. This produces a fairly nice and lumpy, angular terrain kind of similar to something you'd see in old Atari/Amiga or DOS '3D' games (think Virus/Zarch on the Atari ST). I'm now trying to work out how to do collision with the terrain, testing to see if the player is about to collide with a piece of scenery sticking upwards or fall into a hole. At the moment I am simply dividing the player's co-ordinates by the gridsize to find which vertex the player is on top of and it works well when the player is exactly over the corner of a triangle piece of terrain. However... How can I make it more accurate for the bits between the vertices? I get confused since they don't exist in my heightmap data, they're a product of the GPU trying to draw a triangle between three points. I can calculate the height of the point closest to the player, but not the space between them. I.e if the player is hovering over the centre of one of these 'quads', rather than over the corner vertex of one, how do I work out the height of the terrain below them? Later on I may want the player to slide down the slopes in the terrain.

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• Unity: Assigning String value in inspector

  - by Marc Pilgaard

  I got an issue with Unity I can't seem to comprehend, and it is possibly very simple: I am trying to write a simple piece of code in JavaScript where a button toggles the activation of a shield, by dragging a prefab with Resources.load("ActivateShieldPreFab") and destroying it again (Haven't implemented that yet). I wish to assign this button through the inspector, so I have created a string variable which appears as intended in the inspector. Though it doesn't seem to register the inspector input, even though I changed the value through the inspector. It only provides the error: "Input Key named: is unknown" When the button name is assigned within the code, there is no issues. Code as follows: var ShieldOn = false; var stringbutton : String; function Start(){ } function Update () { if(Input.GetKey(stringbutton) && ShieldOn != true) { Instantiate(Resources.load("ActivateShieldPreFab"), Vector3 (0, 0, 0), Quaternion.identity); ShieldOn = true; } } Hope somebody can help, in advance... Thanks

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• What library for octrees or kd-trees?

  - by Will

  Are there any robust performant libraries for indexing objects? It would need frustum culling and visiting objects hit by a ray as well as neighbourhood searches. I can find lots of articles showing the math for the component parts, often as algebra rather than simple C, but nothing that puts it all together (apart from perhaps Ogre, which has rather more involved and isn't so stand-alone). Surely hobby game makers don't all have to make their own octrees? (Python or C/C++ w/bindings preferred)

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