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• exact point on a rotating sphere

  - by nkint

  I have a sphere that represents the Earth textured with real pictures. It's rotating around the x axis, and when user click down it has to show me the exact place he clicked on. For example if he clicked on Singapore the system should be able to: understand that user clicked on the sphere (OK, I'll do it with unProject) understand where user clicked on the sphere (ray-sphere collision?) and take into account the rotation transform sphere-coordinate to some coordinate system good for some web-api service ask to api (OK, this is the simpler thing for me ;-) some advice?

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• Drawing texture does not work anymore with a small amount of triangles

  - by Paul

  When i draw lines, the vertices are well connected. But when i draw the texture inside the triangles, it only works with i<4 in the for loop, otherwise with i<5 for example, there is a EXC_BAD_ACCESS message, at @synthesize textureImage = _textureImage. I don't understand why. (The generatePolygons method seems to work fine as i tried to draw lines with many vertices as in the second image below. And textureImage remains the same for i<4 or i<5 : it's a 512px square image). Here are the images : What i want to achieve is to put the red points and connect them to the y-axis (the green points) and color the area (the green triangles) : If i only draw lines, it works fine : Then with a texture color, it works for i<4 in the loop (the red points in my first image, plus the fifth one to connect the last y) : But then, if i set i<5, the debug tool says EXC_BAD_ACCESS at the synthesize of _textureImage. Here is my code : I set a texture color in HelloWordLayer.mm with : CCSprite *textureImage = [self spriteWithColor:color3 textureSize:512]; _terrain.textureImage = textureImage; Then in the class Terrain, i create the vertices and put the texture in the draw method : @implementation Terrain @synthesize textureImage = _textureImage; //EXC_BAD_ACCESS for i<5 - (void)generatePath2{ CGSize winSize = [CCDirector sharedDirector].winSize; float x = 40; float y = 0; for(int i = 0; i < kMaxKeyPoints+1; ++i) { _hillKeyPoints[i] = CGPointMake(x, y); x = 150 + (random() % (int) 30); y += 30; } } -(void)generatePolygons{ _nPolyVertices = 0; float x1 = 0; float y1 = 0; int keyPoints = 0; for (int i=0; i<4; i++){ /* HERE : 4 = OK / 5 = crash */ //V0: at (0,0) _polyVertices[_nPolyVertices] = CGPointMake(x1, y1); _polyTexCoords[_nPolyVertices++] = CGPointMake(x1, y1); //V1: to the first "point" _polyVertices[_nPolyVertices] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y); _polyTexCoords[_nPolyVertices++] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y); keyPoints++; //from point at index 0 to 1 //V2, same y as point n°2: _polyVertices[_nPolyVertices] = CGPointMake(0, _hillKeyPoints[keyPoints].y); _polyTexCoords[_nPolyVertices++] = CGPointMake(0, _hillKeyPoints[keyPoints].y); //V1 again _polyVertices[_nPolyVertices] = _polyVertices[_nPolyVertices-2]; _polyTexCoords[_nPolyVertices++] = _polyVertices[_nPolyVertices-2]; //V2 again _polyVertices[_nPolyVertices] = _polyVertices[_nPolyVertices-2]; _polyTexCoords[_nPolyVertices++] = _polyVertices[_nPolyVertices-2]; //V3 = same x,y as point at index 1 _polyVertices[_nPolyVertices] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y); _polyTexCoords[_nPolyVertices] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y); y1 = _polyVertices[_nPolyVertices].y; _nPolyVertices++; } } - (id)init { if ((self = [super init])) { [self generatePath2]; [self generatePolygons]; } return self; } - (void) draw { //glDisable(GL_TEXTURE_2D); glDisableClientState(GL_COLOR_ARRAY); glDisableClientState(GL_TEXTURE_COORD_ARRAY); glBindTexture(GL_TEXTURE_2D, _textureImage.texture.name); glColor4f(1, 1, 1, 1); glVertexPointer(2, GL_FLOAT, 0, _polyVertices); glTexCoordPointer(2, GL_FLOAT, 0, _polyTexCoords); glDrawArrays(GL_TRIANGLE_STRIP, 0, (GLsizei)_nPolyVertices); glColor4f(1, 1, 1, 1); for(int i = 1; i < 40; ++i) { ccDrawLine(_polyVertices[i-1], _polyVertices[i]); } // restore default GL states glEnable(GL_TEXTURE_2D); glEnableClientState(GL_COLOR_ARRAY); glEnableClientState(GL_TEXTURE_COORD_ARRAY); } Do you see anything wrong in this code? Thanks for your help

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• Numerically stable(ish) method of getting Y-intercept of mouse position?

  - by Fraser

  I'm trying to unproject the mouse position to get the position on the X-Z plane of a ray cast from the mouse. The camera is fully controllable by the user. Right now, the algorithm I'm using is... Unproject the mouse into the camera to get the ray: Vector3 p1 = Vector3.Unproject(new Vector3(x, y, 0), 0, 0, width, height, nearPlane, farPlane, viewProj; Vector3 p2 = Vector3.Unproject(new Vector3(x, y, 1), 0, 0, width, height, nearPlane, farPlane, viewProj); Vector3 dir = p2 - p1; dir.Normalize(); Ray ray = Ray(p1, dir); Then get the Y-intercept by using algebra: float t = -ray.Position.Y / ray.Direction.Y; Vector3 p = ray.Position + t * ray.Direction; The problem is that the projected position is "jumpy". As I make small adjustments to the mouse position, the projected point moves in strange ways. For example, if I move the mouse one pixel up, it will sometimes move the projected position down, but when I move it a second pixel, the project position will jump back to the mouse's location. The projected location is always close to where it should be, but it does not smoothly follow a moving mouse. The problem intensifies as I zoom the camera out. I believe the problem is caused by numeric instability. I can make minor improvements to this by doing some computations at double precision, and possibly abusing the fact that floating point calculations are done at 80-bit precision on x86, however before I start micro-optimizing this and getting deep into how the CLR handles floating point, I was wondering if there's an algorithmic change I can do to improve this? EDIT: A little snooping around in .NET Reflector on SlimDX.dll: public static Vector3 Unproject(Vector3 vector, float x, float y, float width, float height, float minZ, float maxZ, Matrix worldViewProjection) { Vector3 coordinate = new Vector3(); Matrix result = new Matrix(); Matrix.Invert(ref worldViewProjection, out result); coordinate.X = (float) ((((vector.X - x) / ((double) width)) * 2.0) - 1.0); coordinate.Y = (float) -((((vector.Y - y) / ((double) height)) * 2.0) - 1.0); coordinate.Z = (vector.Z - minZ) / (maxZ - minZ); TransformCoordinate(ref coordinate, ref result, out coordinate); return coordinate; } // ... public static void TransformCoordinate(ref Vector3 coordinate, ref Matrix transformation, out Vector3 result) { Vector3 vector; Vector4 vector2 = new Vector4 { X = (((coordinate.Y * transformation.M21) + (coordinate.X * transformation.M11)) + (coordinate.Z * transformation.M31)) + transformation.M41, Y = (((coordinate.Y * transformation.M22) + (coordinate.X * transformation.M12)) + (coordinate.Z * transformation.M32)) + transformation.M42, Z = (((coordinate.Y * transformation.M23) + (coordinate.X * transformation.M13)) + (coordinate.Z * transformation.M33)) + transformation.M43 }; float num = (float) (1.0 / ((((transformation.M24 * coordinate.Y) + (transformation.M14 * coordinate.X)) + (coordinate.Z * transformation.M34)) + transformation.M44)); vector2.W = num; vector.X = vector2.X * num; vector.Y = vector2.Y * num; vector.Z = vector2.Z * num; result = vector; } ...which seems to be a pretty standard method of unprojecting a point from a projection matrix, however this serves to introduce another point of possible instability. Still, I'd like to stick with the SlimDX Unproject routine rather than writing my own unless it's really necessary.

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• Isometric layer moving inside map

  - by gronzzz

  i'm created isometric map and now trying to limit layer moving. Main idea, that i have left bottom, right bottom, left top, right top points, that camera can not move outside, so player will not see map out of bounds. But i can not understand algorithm of how to do that. It's my layer scale/moving code. - (void)touchBegan:(UITouch *)touch withEvent:(UIEvent *)event { _isTouchBegin = YES; } - (void)touchMoved:(UITouch *)touch withEvent:(UIEvent *)event { NSArray *allTouches = [[event allTouches] allObjects]; UITouch *touchOne = [allTouches objectAtIndex:0]; CGPoint touchLocationOne = [touchOne locationInView: [touchOne view]]; CGPoint previousLocationOne = [touchOne previousLocationInView: [touchOne view]]; // Scaling if ([allTouches count] == 2) { _isDragging = NO; UITouch *touchTwo = [allTouches objectAtIndex:1]; CGPoint touchLocationTwo = [touchTwo locationInView: [touchTwo view]]; CGPoint previousLocationTwo = [touchTwo previousLocationInView: [touchTwo view]]; CGFloat currentDistance = sqrt( pow(touchLocationOne.x - touchLocationTwo.x, 2.0f) + pow(touchLocationOne.y - touchLocationTwo.y, 2.0f)); CGFloat previousDistance = sqrt( pow(previousLocationOne.x - previousLocationTwo.x, 2.0f) + pow(previousLocationOne.y - previousLocationTwo.y, 2.0f)); CGFloat distanceDelta = currentDistance - previousDistance; CGPoint pinchCenter = ccpMidpoint(touchLocationOne, touchLocationTwo); pinchCenter = [self convertToNodeSpace:pinchCenter]; CGFloat predictionScale = self.scale + (distanceDelta * PINCH_ZOOM_MULTIPLIER); if([self predictionScaleInBounds:predictionScale]) { [self scale:predictionScale scaleCenter:pinchCenter]; } } else { // Dragging _isDragging = YES; CGPoint previous = [[CCDirector sharedDirector] convertToGL:previousLocationOne]; CGPoint current = [[CCDirector sharedDirector] convertToGL:touchLocationOne]; CGPoint delta = ccpSub(current, previous); self.position = ccpAdd(self.position, delta); } } - (void)touchEnded:(UITouch *)touch withEvent:(UIEvent *)event { _isDragging = NO; _isTouchBegin = NO; // Check if i need to bounce _touchLoc = [touch locationInNode:self]; } #pragma mark - Update - (void)update:(CCTime)delta { CGPoint position = self.position; float scale = self.scale; static float friction = 0.92f; //0.96f; if(_isDragging && !_isScaleBounce) { _velocity = ccp((position.x - _lastPos.x)/2, (position.y - _lastPos.y)/2); _lastPos = position; } else { _velocity = ccp(_velocity.x * friction, _velocity.y *friction); position = ccpAdd(position, _velocity); self.position = position; } if (_isScaleBounce && !_isTouchBegin) { float min = fabsf(self.scale - MIN_SCALE); float max = fabsf(self.scale - MAX_SCALE); int dif = max > min ? 1 : -1; if ((scale > MAX_SCALE - SCALE_BOUNCE_AREA) || (scale < MIN_SCALE + SCALE_BOUNCE_AREA)) { CGFloat newSscale = scale + dif * (delta * friction); [self scale:newSscale scaleCenter:_touchLoc]; } else { _isScaleBounce = NO; } } }

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• Java: Reflection Packet Builder using getField()

  - by Matchlighter

  So I just finished writing a packet builder that dynamically loads data into a data stream which is then sent out. Each builder operates by finding fields in its class (and its superclasses) that are marked with an @data annotation. Upon finishing the builder, I remembered that getFields() does not return in "any specific order". I quite like my builder because it allows for quite simple, yet hard-typed packets. Could this implementation be a problem? What would be the best next step to keep the simplicity - do alphabetical sorting of fields?

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• Collision within a poly

  - by G1i1ch

  For an html5 engine I'm making, for speed I'm using a path poly. I'm having trouble trying to find ways to get collision with the walls of the poly. To make it simple I just have a vector for the object and an array of vectors for the poly. I'm using Cartesian vectors and they're 2d. Say poly = [[550,0],[169,523],[-444,323],[-444,-323],[169,-523]], it's just a pentagon I generated. The object that will collide is object, object.pos is it's position and object.vel is it's velocity. They're both 2d vectors too. I've had some success to get it to find a collision, but it's just black box code I ripped from a c++ example. It's very obscure inside and all it does though is return true/false and doesn't return what vertices are collided or collision point, I'd really like to be able to understand this and make my own so I can have more meaningful collision. I'll tackle that later though. Again the question is just how does one find a collision to walls of a poly given you know the poly vertices and the object's position + velocity? If more info is needed please let me know. And if all anyone can do is point me to the right direction that's great.

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• How to create a copy of an instance without having access to private variables

  - by Jamie

  Im having a bit of a problem. Let me show you the code first: public class Direction { private CircularList xSpeed, zSpeed; private int[] dirSquare = {-1, 0, 1, 0}; public Direction(int xSpeed, int zSpeed){ this.xSpeed = new CircularList(dirSquare, xSpeed); this.zSpeed = new CircularList(dirSquare, zSpeed); } public Direction(Point dirs){ this(dirs.x, dirs.y); } public void shiftLeft(){ xSpeed.shiftLeft(); zSpeed.shiftRight(); } public void shiftRight(){ xSpeed.shiftRight(); zSpeed.shiftLeft(); } public int getXSpeed(){ return this.xSpeed.currentValue(); } public int getZSpeed(){ return this.zSpeed.currentValue(); } } Now lets say i have an instance of Direction: Direction dir = new Direction(0, 0); As you can see in the code of Direction, the arguments fed to the constructor, are passed directly to some other class. One cannot be sure if they stay the same because methods shiftRight() and shiftLeft could have been called, which changes thos numbers. My question is, how do i create a completely new instance of Direction, that is basically copy(not by reference) of dir? The only way i see it, is to create public methods in both CircularList(i can post the code of this class, but its not relevant) and Direction that return the variables needed to create a copy of the instance, but this solution seems really dirty since those numbers are not supposed to be touched after beeing fed to the constructor, and therefore they are private.

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• Maya Animated Character export for XNA 4.0 problem

  - by FahidK

  To begin with, I'm trying to export an animated character in .fbx format from Maya 2013 to XNA 4.0 In Maya, The Model has a basic rig and the animations are in clips made in the Trax editor. so the issue i'm having is after selecting the model and the root joint and then hitting export in .fbx format, for some reason when i open the exported .fbx file the joint system is detached from the model with no animation. Btw, i have the animations in clips so that they can be called in code, for example "run","walk","attack". So, what can i do to solve this problem? Thank you.

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• How to remove a box2d body when collision happens?

  - by Ayham

  I’m still new to java and android programming and I am having so much trouble Removing an object when collision happens. I looked around the web and found that I should never handle removing BOX2D bodies during collision detection (a contact listener) and I should add my objects to an arraylist and set a variable in the User Data section of the body to delete or not and handle the removing action in an update handler. So I did this: First I define two ArrayLists one for the faces and one for the bodies: ArrayList<Sprite> myFaces = new ArrayList<Sprite>(); ArrayList<Body> myBodies = new ArrayList<Body>(); Then when I create a face and connect that face to its body I add them to their ArrayLists like this: face = new AnimatedSprite(pX, pY, pWidth, pHeight, this.mBoxFaceTextureRegion); Body BoxBody = PhysicsFactory.createBoxBody(mPhysicsWorld, face, BodyType.DynamicBody, objectFixtureDef); mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(face, BoxBody, true, true)); myFaces.add(face); myBodies.add(BoxBody); now I add a contact listener and an update handler in the onloadscene like this: this.mPhysicsWorld.setContactListener(new ContactListener() { private AnimatedSprite face2; @Override public void beginContact(final Contact pContact) { } @Override public void endContact(final Contact pContact) { } @Override public void preSolve(Contact contact,Manifold oldManifold) { } @Override public void postSolve(Contact contact,ContactImpulse impulse) { } }); scene.registerUpdateHandler(new IUpdateHandler() { @Override public void reset() { } @Override public void onUpdate(final float pSecondsElapsed) { } }); My plan is to detect which two bodies collided in the contact listener by checking a variable from the user data section of the body, get their numbers in the array list and finally use the update handler to remove these bodies. The questions are: Am I using the arraylist correctly? How to add a variable to the User Data (the code please). I tried removing a body in this update handler but it still throws me NullPointerException , so what is the right way to add an update handler and where should I add it. Any other advices to do this would be great. Thanks in advance.

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• How to calculate vertext normals for a mesh in Java in OpenGL ES application?

  - by alan mc

  Can some one point me to Java code ( in Java not C or C++) that calculates all the normals for all the vertices of a mesh for OpenGL ES application. I need this for lighting. Lets say I have a cube with following vertices and indices: float vertices[] = { -width, -height, -depth, // 0 width, -height, -depth, // 1 width, height, -depth, // 2 -width, height, -depth, // 3 -width, -height, depth, // 4 width, -height, depth, // 5 width, height, depth, // 6 -width, height, depth // 7 }; short indices[] = { 0, 2, 1, 0, 3, 2, 1,2,6, 6,5,1, 4,5,6, 6,7,4, 2,3,6, 6,3,7, 0,7,3, 0,4,7, 0,1,5, 0,5,4 }; In above specific example how many normals we need ?

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• samplerCubeShadow and texture offset

  - by Irbis

  I use sampler2DShadow when accessing a single shadow map. I create PCF in this way: result += textureProjOffset(ShadowSampler, ShadowCoord, ivec2(-1,-1)); result += textureProjOffset(ShadowSampler, ShadowCoord, ivec2(-1,1)); result += textureProjOffset(ShadowSampler, ShadowCoord, ivec2(1,1)); result += textureProjOffset(ShadowSampler, ShadowCoord, ivec2(1,-1)); result = result * 0.25; For a cube map I use samplerCubeShadow: result = texture(ShadowCubeSampler, vec4(normalize(position), depth)); How to adopt above PCF when accessing a cube map ?

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• Beginner C# image loading woes - NullReferenceException

  - by Seth Taddiken

  I keep getting a "NullReferenceExeption was unhandled" with "Object reference not set to an instance of an object." written under it. I have all of the images (png) correct with names and added to references. protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); backGround = Content.Load<Texture2D>("Cracked"); player1.playerBlock = Content.Load<Texture2D>("square"); player2.playerBlock = Content.Load<Texture2D>("square2"); }

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• How to handle animations?

  - by Bane

  I am coding a simple 2D engine to be used with HTML5. I already have classes such as Picture, Scene, Camera and Renderer, but now I need to work on Animations. Picture is basocally a wrapper for a normal image object, with it's own draw method, but this is unrelated, I'm interested in how animation in 2D games is usually done. What I planned to do, is to have the Animation class as well act like a wrapper for a few image objects, and then have methods such as getCurrentImage, next and animate (which would use intervals to quickly change the current image). I meant to feed the animation a couple of PNG's at inicialisation. Is quickly swapping PNG images acceptable for 2D animation? Are there some standard ways of doing this, or are there flaws in my ways?

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• Permanently Sync a wiimote with a computer

  - by Adam Geisweit

  i have tried to look up many ways to sync up my wiimotes to my computer so that i can program games with it, but every time it only syncs them up temporarily, or if it says it can permanently sync it, it doesn't actually do it. it gets tiresome when i have to keep on reconnecting it every time i want to save battery life. how would i be able to sync up my wiimote to my computer so that if i turn off my wiimote, i can just hit any button and it will automatically sync it up?

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• What data should be cached in a multiplayer server, relative to AI and players?

  - by DevilWithin

  In a virtual place, fully network driven, with an arbitrary number of players and an arbitrary number of enemies, what data should be cached in the server memory, in order to optimize smooth AI simulation? Trying to explain, lets say player A sees player B to E, and enemy A to G. Each of those players, see player A, but not necessarily each other. Same applies to enemies. Think of this question from a topdown perspective please. In many cases, for example, when a player shoots his gun, the server handles the sound as a radial "signal" that every other entity within reach "hear" and react upon. Doing these searches all the time for a whole area, containing possibly a lot of unrelated players and enemies, seems to be an issue, when the budget for each AI agent is so small. Should every entity cache whatever enters and exits from its radius of awareness? Is there a great way to trace the entities close by without flooding the memory with such caches? What about other AI related problems that may arise, after assuming the previous one works well? We're talking about environments with possibly hundreds of enemies, a swarm.

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• Making body(box2d) a spite(andengine) in android

  - by Kadir

  I can't make body(box2d) a spite(andengine) and at the same time i wanna apply MoveModifier to sprite which is body.if i can make just body,it works namely the srites can collide.if i can apply just MoveModifier to sprites,the sprites can move where i want.but i wanna make body(they can collide) and apply MoveModifier(they can move where i want) at the same time.How can i do? this my code just run MoveModifier not as body at the same time. circles[i] = new Sprite(startX, startY, textRegCircle[i]); body[i] = PhysicsFactory.createCircleBody(physicsWorld, circles[i], BodyType.DynamicBody, FIXTURE_DEF); physicsWorld.registerPhysicsConnector(new PhysicsConnector(circles[i], body[i], true, true)); circles[i].registerEntityModifier( (IEntityModifier) new SequenceEntityModifier ( new MoveModifier(10.0f, circles[i].getX(), circles[i].getX(), circles[i].getY(),CAMERA_HEIGHT+64.0f))); scene.getLastChild().attachChild(circles[i]); scene.registerUpdateHandler(physicsWorld);

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• Circle-Line Collision Detection Problem

  - by jazzdawg

  I am currently developing a breakout clone and I have hit a roadblock in getting collision detection between a ball (circle) and a brick (convex polygon) working correctly. I am using a Circle-Line collision detection test where each line represents and edge on the convex polygon brick. For the majority of the time the Circle-Line test works properly and the points of collision are resolved correctly. Collision detection working correctly. However, occasionally my collision detection code returns false due to a negative discriminant when the ball is actually intersecting the brick. Collision detection failing. I am aware of the inefficiency with this method and I am using axis aligned bounding boxes to cut down on the number of bricks tested. My main concern is if there are any mathematical bugs in my code below. /* * from and to are points at the start and end of the convex polygons edge. * This function is called for every edge in the convex polygon until a * collision is detected. */ bool circleLineCollision(Vec2f from, Vec2f to) { Vec2f lFrom, lTo, lLine; Vec2f line, normal; Vec2f intersectPt1, intersectPt2; float a, b, c, disc, sqrt_disc, u, v, nn, vn; bool one = false, two = false; // set line vectors lFrom = from - ball.circle.centre; // localised lTo = to - ball.circle.centre; // localised lLine = lFrom - lTo; // localised line = from - to; // calculate a, b & c values a = lLine.dot(lLine); b = 2 * (lLine.dot(lFrom)); c = (lFrom.dot(lFrom)) - (ball.circle.radius * ball.circle.radius); // discriminant disc = (b * b) - (4 * a * c); if (disc < 0.0f) { // no intersections return false; } else if (disc == 0.0f) { // one intersection u = -b / (2 * a); intersectPt1 = from + (lLine.scale(u)); one = pointOnLine(intersectPt1, from, to); if (!one) return false; return true; } else { // two intersections sqrt_disc = sqrt(disc); u = (-b + sqrt_disc) / (2 * a); v = (-b - sqrt_disc) / (2 * a); intersectPt1 = from + (lLine.scale(u)); intersectPt2 = from + (lLine.scale(v)); one = pointOnLine(intersectPt1, from, to); two = pointOnLine(intersectPt2, from, to); if (!one && !two) return false; return true; } } bool pointOnLine(Vec2f p, Vec2f from, Vec2f to) { if (p.x >= min(from.x, to.x) && p.x <= max(from.x, to.x) && p.y >= min(from.y, to.y) && p.y <= max(from.y, to.y)) return true; return false; }

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• Calculate the intersection depth between a rectangle and a right triangle

  - by Celarix

  all. I'm working on a 2D platformer built in C#/XNA, and I'm having a lot of problems calculating the intersection depth between a standard rectangle (used for sprites) and a right triangle (used for sloping tiles). Ideally, the rectangle will collide with the solid edges of the triangle, and its bottom-center point will collide with the sloped edge. I've been fighting with this for a couple of days now, and I can't make sense of it. So far, the method detects intersections (somewhat), but it reports wildly wrong depths. How does one properly calculate the depth? Is there something I'm missing? Thanks!

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• Sorting objects before rendering

  - by dreta

  I'm trying to implement a scene graph and in all the articles i've come across there is talk about object sorting. So you'd sort your objects by "material" for example. Now untill i sat down and started implementing it, i kind of took this for granted, because it made sense. But now i'm wondering what does sorting actually change? In my engine, i have a manager for UBOs, i use those to store data that'll be shared between programs, at the moment that only involves time, camera and projection matrices and lights (i'm not worrying about managing which lights affect which objects ATM). Now for each model i have to change the model to world matrix uniform, no sorting is going to change that. So is the jump from changing this matrix to also setting a material for each object that bad? I vaguely remember reading somewhere that each time you change something in the pipeline, it has to get flushed and that can cause performance issues. But for each drawing call i'm setting up a model to world matrix anyway, so what sense does it make to ever be concerned about this? BTW is there any information about whether changing a uniform and calling glBufferSubData is more (or less) expensive.

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• How to make room reflection using Cubemap

  - by MaT

  I am trying to use a cube map of the inside of a room to create some reflections on walls, ceiling and floor. But when I use the cube map, the reflected image is not correct. The point of view seems to be false. To be correct I use a different cube map for each walls, floor or ceiling. The cube map is calculated from the center of the plane looking at the room. Are there specialized techniques to achieve such effect ? Thanks a lot !

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• Creating a voxel chunk with a VBO - How to translate the coordinates of each block and add it to the VBO chunk?

  - by sunsunsunsunsun

  Im trying to make a voxel engine similar to minecraft as a little learning experience and a way to learn some opengl. I have created a chunk class and I want to put all of the vertices for the whole chunk into a single VBO. I was previously only putting each block into a vbo and making a call to render each block. Anyways, I am a bit confused about how I can translate the coordinates of each block in the chunk when I'm putting all vertices into one vbo. This is what I have at the moment. public void putVertices(float tx, float ty, float tz) { float l_length = 1.0f; float l_height = 1.0f; float l_width = 1.0f; vertexPositionData.put(new float[]{ xOffset + l_length + tx, l_height + ty, zOffset + -l_width + tz, xOffset + -l_length + tx, l_height + ty, zOffset + -l_width + tz, xOffset + -l_length + tx, l_height + ty, zOffset + l_width + tz, xOffset + l_length + tx, l_height + ty, zOffset + l_width + tz, xOffset + l_length + tx, -l_height + ty, zOffset + l_width + tz, xOffset + -l_length + tx, -l_height + ty, zOffset + l_width + tz, xOffset + -l_length + tx, -l_height + ty, zOffset + -l_width + tz, xOffset + l_length + tx, -l_height + ty, zOffset + -l_width + tz, xOffset + l_length + tx, l_height + ty, zOffset + l_width + tz, xOffset + -l_length + tx, l_height + ty,zOffset + l_width + tz, xOffset + -l_length + tx, -l_height + ty,zOffset + l_width + tz, xOffset + l_length + tx, -l_height + ty, zOffset + l_width + tz, xOffset + l_length + tx, -l_height + ty, zOffset + -l_width + tz, xOffset + -l_length + tx, -l_height + ty,zOffset + -l_width + tz, xOffset + -l_length + tx, l_height + ty, zOffset + -l_width + tz, xOffset + l_length + tx, l_height + ty, zOffset + -l_width + tz, xOffset + -l_length + tx, l_height + ty, zOffset + l_width + tz, xOffset + -l_length + tx, l_height + ty, zOffset + -l_width + tz, xOffset + -l_length + tx, -l_height + ty, zOffset + -l_width + tz, xOffset + -l_length + tx, -l_height + ty,zOffset + l_width + tz, xOffset + l_length + tx, l_height + ty,zOffset + -l_width + tz, xOffset + l_length + tx, l_height + ty, zOffset + l_width + tz, xOffset + l_length + tx, -l_height + ty, zOffset + l_width + tz, xOffset + l_length + tx, -l_height + ty, zOffset + -l_width + tz }); } public void createChunk() { vertexPositionData = BufferUtils.createFloatBuffer((24*3)*activateBlocks); Random random = new Random(); for (int x = 0; x < CHUNK_SIZE; x++) { for (int y = 0; y < CHUNK_SIZE; y++) { for (int z = 0; z < CHUNK_SIZE; z++) { if(blocks[x][y][z].getActive()) { putVertices(x*2.0f, y*2.0f, z*2.0f); } } } } Whats any easy way to translate the vertices of each block into its correct position? I was previously using glTranslatef with each call to render block but this wont work now. What I am doing now also does not work, the blocks all render in stacks on top of each other and it looks like this: http://i.imgur.com/NyFtBTI.png Thanks

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• Tile-wide extent tracing on a grid.

  - by Larolaro

  I'm currently working on A* pathfinding on a grid and I'm looking to smooth the generated path, while also considering the extent of the character moving along it. I'm using a grid for the pathfinding, however character movement is free roaming, not strict tile to tile movement. To achieve a smoother, more efficient path, I'm doing line traces on a grid to determine if there is unwalkable tiles between tiles to shave off unecessary corners. However, because a line trace is zero extent, it doesn't consider the extent of the character and gives bad results (not returning unwalkable tiles just missed by the line, causing unwanted collisions). So what I'm looking for is rather than a line algorithm that determines the tiles under it, I'm looking for one that determines the tiles under a tile-wide extent line. Here is an image to help visualise my problem! Does anyone have any ideas? I've been working with Bresenham's line and other alternatives but I haven't yet figured out how to nail this specific problem.

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• how can i get rotation vector from matrix4x4 in xna?

  - by mr.Smyle

  i want to get rotation vector from matrix to realize some parent-children system for models. Matrix bonePos = link.Bone.Transform * World; Matrix m = Matrix.CreateTranslation(link.Offset) * Matrix.CreateScale(link.gameObj.Scale.X, link.gameObj.Scale.Y, link.gameObj.Scale.Z) * Matrix.CreateFromYawPitchRoll(MathHelper.ToRadians(link.gameObj.Rotation.Y), MathHelper.ToRadians(link.gameObj.Rotation.X), MathHelper.ToRadians(link.gameObj.Rotation.Z)) //need rotation vector from bone matrix here (now it's global model rotation vector) * Matrix.CreateFromYawPitchRoll(MathHelper.ToRadians(Rotation.Y), MathHelper.ToRadians(Rotation.X), MathHelper.ToRadians(Rotation.Z)) * Matrix.CreateTranslation(bonePos.Translation); link.gameObj.World = m; where : link - struct with children model settings, like position, rotation etc. And link.Bone - Parent Bone

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• cocos2d/OpenGL multitexturing problem

  - by Gajoo

  I've got a simple shader to test multitextureing the problem is both samplers are using same image as their reference. the shader code is basically just this : vec4 mid = texture2D(u_texture,v_texCoord); float g = texture2D(u_guide,v_guideCoord); gl_FragColor = vec4(g , mid.g,0,1); and this is how I'm calling draw function : int last_State; glGetIntegerv(GL_ACTIVE_TEXTURE, &last_State); glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, getTexture()->getName()); glActiveTexture(GL_TEXTURE1); glEnable(GL_TEXTURE_2D); glBindTexture(GL_TEXTURE_2D, mGuideTexture->getName()); ccGLEnableVertexAttribs( kCCVertexAttribFlag_TexCoords |kCCVertexAttribFlag_Position); glVertexAttribPointer(kCCVertexAttrib_Position, 2, GL_FLOAT, GL_FALSE, 0, vertices); glVertexAttribPointer(kCCVertexAttrib_TexCoords, 2, GL_FLOAT, GL_FALSE, 0, texCoord); glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); glDisable(GL_TEXTURE_2D); I've already check mGuideTexture->getName() and getTexture()->getName() are returning correct textures. but looking at the result I can tell, both samplers are reading from getTexture()->getName(). here are some screen shots showing what is happening : The image rendered Using above codes The image rendered when I change textures passed to samples I'm expecting to see green objects from the first picture with red objects hanging from the top.

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• Rotation and translation like in GTA 1 OpenGL

  - by user1876377

  Okay, so I have a figure in XZ plain. I want to move it forward/backward and rotate at it's own Y axis, then move forward again in the rotation's direction, like the character in GTA 1. Code so far: Init: spaceship_position = glm::vec3(0,0,0); spaceship_rotation = glm::vec3(0,0,0); spaceship_scale = glm::vec3(1, 1, 1); Draw: glm::mat4 transform = glm::scale<float>(spaceship_scale) * glm::rotate<float>(spaceship_rotation.x, 1, 0, 0) * glm::rotate<float>(spaceship_rotation.y, 0, 1, 0) * glm::rotate<float>(spaceship_rotation.z, 0, 0, 1) * glm::translate<float>(spaceship_position); drawMesh(spaceship, texture, transform); Update: switch (key.keysym.sym) { case SDLK_UP: spaceship_position.z += 0.1; break; case SDLK_DOWN: spaceship_position.z -= 0.1; break; case SDLK_LEFT: spaceship_rotation.y += 1; break; case SDLK_RIGHT: spaceship_rotation.y -= 1; break; } So this only moves on the Z axis, but how can I move the object on both Z and X axis where the object is facing?

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