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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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• Asset missing problem XNA

  - by ChocoMan

  I'm using VS2010 with XNA 4.0 and I'm trying to load an FBX model with texture on the screen. The problem I'm having is this error: Missing Asset: C:\Users\ChocoMan\Documents\Visual Studio 2010\Projects\XNAGame\Documents\Visual Studio\Projects\XNAGame\XNAGameContent\Textures\texture.bmp but the actual path to the texture is C:\Users\ChocoMan\Documents\Visual Studio\Projects\XNAGame\XNAGameContent\Textures\texture.bmp Also, when I linked the texture in Maya, I used the above address. Does anyone know why VS is looking for an incorrect address that doesnt exist?

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• Transforming a primitive tetrahedron into a primitive icosahedron?

  - by Djentleman

  I've created a tetrahedron by creating a BoundingBox and building the faces of the tetrahedron within the bounding box as follows (see image as well): VertexPositionNormalTexture[] vertices = new VertexPositionNormalTexture[12]; BoundingBox box = new BoundingBox(new Vector3(-1f, 1f, 1f), new Vector3(1f, -1f, -1f)); vertices[0].Position = box.GetCorners()[0]; vertices[1].Position = box.GetCorners()[2]; vertices[2].Position = box.GetCorners()[7]; vertices[3].Position = box.GetCorners()[0]; vertices[4].Position = box.GetCorners()[5]; vertices[5].Position = box.GetCorners()[2]; vertices[6].Position = box.GetCorners()[5]; vertices[7].Position = box.GetCorners()[7]; vertices[8].Position = box.GetCorners()[2]; vertices[9].Position = box.GetCorners()[5]; vertices[10].Position = box.GetCorners()[0]; vertices[11].Position = box.GetCorners()[7]; What would I then have to do to transform this tetrahedron into an icosahedron? Similar to this image: I understand the concept but applying it is another thing entirely for me.

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• Blur gets displaced compared to original image

  - by user1294203

  I have implemented a SSAO and I'm using a blur step to smooth it out. The problem is that the blurred texture is slightly displaced compared to the original. I'm blurring using a 4x4 kernel since that was my noise kernel in SSAO. The following is the blurring shader: float result = 0.0; for(int i = 0; i < 4; i++){ for(int j = 0; j < 4; j++){ vec2 offset = vec2(TEXEL_SIZE.x * i, TEXEL_SIZE.y * j); result += texture(aoSampler, TexCoord + offset).r; } } out_AO = vec4(vec3(0.0), result * 0.0625); Where TEXEL_SIZE is one over my window resolution. I was thinking that this is was an error based on how OpenGL counts the Texel center, so I tried displacing the texture coordinate I was using by 0.5 * TEXEL_SIZE, but there was still a slight displacement. The texture input to my blur shader, has wrap parameters: glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP); When I tell the blur shader to just output the the value of the pixel, the result is not displaced, so it must have something to do with how neighboring pixels are sampled. Any thoughts?

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• Animate from end frame of one animation to end frame of another Unity3d/C#

  - by Timothy Williams

  So I have two legacy FBX animations; Animation A and Animation B. What I'm looking to do is to be able to fade from A to B regardless of the current frame A is on. Using animation.CrossFade() will play A in reverse until it reaches frame 0, then play B forward. What I'm looking to do is blend from the current frame of A to the end frame of B. Probably via some sort of lerp between the facial position in A and the facial position in the last frame of B. Does anyone know how I might be able to accomplish this? Either via a built in function or potentially lerping of some sort?

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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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• About Alpha blending sprites in Direct3D9

  - by ambrozija

  I have a Direct3D9 application that is rendering ID3DXSprites. The problem I am experiencing is best described in this situation: I have a texture that is totally opaque. On top of it I draw a rectangle filled with solid color and alpha of 128. On top of the rectangle I have a text that is totally opaque. I draw all of this and get the resulting image through GetRenderTarget call. The problem is that on the resulting image, on the area where the transparent rectangle is, I have semi transparent pixels. It is not a problem that the rectangle is transparent, the problem is that the resulting image is. The question is how to setup the blending so in this situation I don't get the transparent pixels in the resulting image? I use the sprite with D3DXSPRITE_ALPHABLEND which sets the device state to D3DBLEND_SRCALPHA and D3DBLEND_INVSRCALPHA. I tried couple of combinations of SetRenderState, like D3DBLEND_SRCALPHA, D3DBLEND_DESTALPHA etc., but couldn't make it work. Thanks.

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• How to I access "Deny" message from a Lidgren client?

  - by TJ Mott

  I'm using the Lidgren v3 network for a UDP client/server networking model. On the server end, I'm initializing a NetServer object with the NetIncomingMessage.ConnectionApproval message type enabled. So the client is able to successfully connect and the first packet it sends is a login packet, containing a username and password supplied by the user. The server is receiving that and doing some black magic to authenticate, and everything works up to that point. If the login fails, the server calling NetIncomingMessage.SenderConnection.Deny("Invalid Login Credentials"). I want to know how to properly receive this deny message on the client. I'm getting the message, it shows up with a message type of NetIncomingMessage.StatusChanged. If I call ReadString on that message, I get a corrupted version of the string I passed to the Deny method on the server. The type of corruption varies, I've seen odd characters in there but in every case it's truncated and is way shorter than the string I entered. Any ideas? The official documentation is sparse on this topic. I could use pointers from anyone who has successfully used the Lidgren library and uses the Accept or Deny methods. Also, if I don't do any authentication and just Approve() the connection every time, stuff actually works just fine and I'm getting reliable two-way UDP traffic. (And lastly, Stack Exchange said I don't have enough reputation to use the "Lidgren" tag....???)

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• Scrolling background stops after awhile?

  - by Lewis

  Can anyone tell me where my maths is wrong please, it stops scrolling after awhile. if (background.position.y < background2.position.y) { background.position = ccp(background.contentSize.width / 2, background.position.y - 50 * delta); background2.position = ccp(background.contentSize.width / 2, background.position.y + background.contentSize.height); } else { background.position = ccp(background2.contentSize.width / 2, background2.position.y - 50 * delta); background.position = ccp(background2.contentSize.width / 2, background2.position.y + background.contentSize.height); } //reset if (background.position.y <-background.contentSize.height / 2) { background.position = ccp(background.contentSize.width / 2 ,background2.position.y + background2.contentSize.height); } else if (background2.position.y < -background2.contentSize.height / 2) { background2.position = ccp(background2.contentSize.width / 2, background.position.y + background.contentSize.height); }

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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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• Issues with touch buttons in XNA (Release state to be precise)

  - by Aditya

  I am trying to make touch buttons in WP8 with all the states (Pressed, Released, Moved), but the TouchLocationState.Released is not working. Here's my code: Class variables: bool touching = false; int touchID; Button tempButton; Button is a separate class with a method to switch states when touched. The Update method contains the following code: TouchCollection touchCollection = TouchPanel.GetState(); if (!touching && touchCollection.Count > 0) { touching = true; foreach (TouchLocation location in touchCollection) { for (int i = 0; i < menuButtons.Count; i++) { touchID = location.Id; // store the ID of current touch Point touchLocation = new Point((int)location.Position.X, (int)location.Position.Y); // create a point Button button = menuButtons[i]; if (GetMenuEntryHitBounds(button).Contains(touchLocation)) // a method which returns a rectangle. { button.SwitchState(true); // change the button state tempButton = button; // store the pressed button for accessing later } } } } else if (touchCollection.Count == 0) // clears the state of all buttons if no touch is detected { touching = false; for (int i = 0; i < menuButtons.Count; i++) { Button button = menuButtons[i]; button.SwitchState(false); } } menuButtons is a list of buttons on the menu. A separate loop (within the Update method) after the touched variable is true if (touching) { TouchLocation location; TouchLocation prevLocation; if (touchCollection.FindById(touchID, out location)) { if (location.TryGetPreviousLocation(out prevLocation)) { Point point = new Point((int)location.Position.X, (int)location.Position.Y); if (prevLocation.State == TouchLocationState.Pressed && location.State == TouchLocationState.Released) { if (GetMenuEntryHitBounds(tempButton).Contains(point)) // Execute the button action. I removed the excess } } } } The code for switching the button state is working fine but the code where I want to trigger the action is not. location.State == TouchLocationState.Released mostly ends up being false. (Even after I release the touch, it has a value of TouchLocationState.Moved) And what is more irritating is that it sometimes works! I am really confused and stuck for days now. Is this the right way? If yes then where am I going wrong? Or is there some other more effective way to do this? PS: I also posted this question on stack overflow then realized this question is more appropriate in gamedev. Sorry if it counts as being redundant.

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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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• Draw multiple objects with textures

  - by Simplex

  I want to draw cubes using textures. void OperateWithMainMatrix(ESContext* esContext, GLfloat offsetX, GLfloat offsetY, GLfloat offsetZ) { UserData *userData = (UserData*) esContext->userData; ESMatrix modelview; ESMatrix perspective; //Manipulation with matrix ... glVertexAttribPointer(userData->positionLoc, 3, GL_FLOAT, GL_FALSE, 0, cubeFaces); //in cubeFaces coordinates verticles cube glVertexAttribPointer(userData->normalLoc, 3, GL_FLOAT, GL_FALSE, 0, cubeFaces); //for normals (use in fragment shaider for textures) glEnableVertexAttribArray(userData->positionLoc); glEnableVertexAttribArray(userData->normalLoc); // Load the MVP matrix glUniformMatrix4fv(userData->mvpLoc, 1, GL_FALSE, (GLfloat*)&userData->mvpMatrix.m[0][0]); //Bind base map glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_CUBE_MAP, userData->baseMapTexId); //Set the base map sampler to texture unit to 0 glUniform1i(userData->baseMapLoc, 0); // Draw the cube glDrawArrays(GL_TRIANGLES, 0, 36); } (coordinates transformation is in OperateWithMainMatrix() ) Then Draw() function is called: void Draw(ESContext *esContext) { UserData *userData = esContext->userData; // Set the viewport glViewport(0, 0, esContext->width, esContext->height); // Clear the color buffer glClear(GL_COLOR_BUFFER_BIT); // Use the program object glUseProgram(userData->programObject); OperateWithMainMatrix(esContext, 0.0f, 0.0f, 0.0f); eglSwapBuffers(esContext->eglDisplay, esContext->eglSurface); } This work fine, but if I try to draw multiple cubes (next code for example): void Draw(ESContext *esContext) { ... // Use the program object glUseProgram(userData->programObject); OperateWithMainMatrix(esContext, 2.0f, 0.0f, 0.0f); OperateWithMainMatrix(esContext, 1.0f, 0.0f, 0.0f); OperateWithMainMatrix(esContext, 0.0f, 0.0f, 0.0f); OperateWithMainMatrix(esContext, -1.0f, 0.0f, 0.0f); OperateWithMainMatrix(esContext, -2.0f, 0.0f, 0.0f); eglSwapBuffers(esContext->eglDisplay, esContext->eglSurface); } A side faces overlapes frontal face. The side face of the right cube overlaps frontal face of the center cube. How can i remove this effect and display miltiple cubes without it?

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• How to refactor and improve this XNA mouse input code?

  - by Andrew Price

  Currently I have something like this: public bool IsLeftMouseButtonDown() { return currentMouseState.LeftButton == ButtonState.Pressed && previousMouseSate.LeftButton == ButtonState.Pressed; } public bool IsLeftMouseButtonPressed() { return currentMouseState.LeftButton == ButtonState.Pressed && previousMouseSate.LeftButton == ButtonState.Released; } public bool IsLeftMouseButtonUp() { return currentMouseState.LeftButton == ButtonState.Released && previousMouseSate.LeftButton == ButtonState.Released; } public bool IsLeftMouseButtonReleased() { return currentMouseState.LeftButton == ButtonState.Released && previousMouseSate.LeftButton == ButtonState.Pressed; } This is fine. In fact, I kind of like it. However, I'd hate to have to repeat this same code five times (for right, middle, X1, X2). Is there any way to pass in the button I want to the function so I could have something like this? public bool IsMouseButtonDown(MouseButton button) { return currentMouseState.IsPressed(button) && previousMouseState.IsPressed(button); } public bool IsMouseButtonPressed(MouseButton button) { return currentMouseState.IsPressed(button) && !previousMouseState.IsPressed(button); } public bool IsMouseButtonUp(MouseButton button) { return !currentMouseState.IsPressed(button) && previousMouseState.IsPressed(button); } public bool IsMouseButtonReleased(MouseButton button) { return !currentMouseState.IsPressed(button) && previousMouseState.IsPressed(button); } I suppose I could create some custom enumeration and switch through it in each function, but I'd like to first see if there is a built-in solution or a better way.. Thanks!

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• Unity: parallel vectors and cross product, how to compare vectors

  - by Heisenbug

  I read this post explaining a method to understand if the angle between 2 given vectors and the normal to the plane described by them, is clockwise or anticlockwise: public static AngleDir GetAngleDirection(Vector3 beginDir, Vector3 endDir, Vector3 upDir) { Vector3 cross = Vector3.Cross(beginDir, endDir); float dot = Vector3.Dot(cross, upDir); if (dot > 0.0f) return AngleDir.CLOCK; else if (dot < 0.0f) return AngleDir.ANTICLOCK; return AngleDir.PARALLEL; } After having used it a little bit, I think it's wrong. If I supply the same vector as input (beginDir equal to endDir), the cross product is zero, but the dot product is a little bit more than zero. I think that to fix that I can simply check if the cross product is zero, means that the 2 vectors are parallel, but my code doesn't work. I tried the following solution: Vector3 cross = Vector3.Cross(beginDir, endDir); if (cross == Vector.zero) return AngleDir.PARALLEL; And it doesn't work because comparison between Vector.zero and cross is always different from zero (even if cross is actually [0.0f, 0.0f, 0.0f]). I tried also this: Vector3 cross = Vector3.Cross(beginDir, endDir); if (cross.magnitude == 0.0f) return AngleDir.PARALLEL; it also fails because magnitude is slightly more than zero. So my question is: given 2 Vector3 in Unity, how to compare them? I need the elegant equivalent version of this: if (beginDir.x == endDir.x && beginDir.y == endDir.y && beginDir.z == endDir.z) return true;

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• How to store character moves (sprite animations)?

  - by Saad

  So I'm thinking about making a small rpg, mainly to test out different design patterns I've been learning about. But the one question that I'm not too sure on how to approach is how to store an array of character moves in the best way possible. So let's say I have arrays of different sprites. This is how I'm thinking about implementing it: array attack = new array (10); array attack2 = new array(5); (loop) //blit some image attack.push(imageInstance); (end loop) Now every time I want the animation I call on attack or attack2; is there a better structure? The problem with this is let's say there are 100 different attacks, and a player can have up to 10 attacks equipped. So how do I tell which attack the user has; should I use a hash map?

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• If I use my own normal values, should I turn off winding order culling?

  - by Phil

  I've discovered that I managed to program a series of boxes with indexed vertices in such a way that every other triangle (Half of each face) has a backwards winding order. As a result, XNA is culling half of them. However, my Vertex objects contain normal data that I have explicitly set, and I am going to implement my own backface culling shortly to reduce the size of the VertexBuffer. Should I turn off winding order culling and manage it myself, or should I make sure the winding order is consistent and let XNA handle it?

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• Combine 3D objects in XNA 4

  - by Christoph

  Currently I am writing on my thesis for university, the theme I am working on is 3D Visualization of hierarchical structures using cone trees. I want to do is to draw a cone and arrange a number of spheres at the bottom of the cone. The spheres should be arranged according to the radius and the number of spheres correctly. As you can imagine I need a lot of these cone/sphere combinations. First Attempt I was able to find some tutorials that helped with drawing cones and spheres. Cone public Cone(GraphicsDevice device, float height, int tessellation, string name, List<Sphere> children) { //prepare children and calculate the children spacing and radius of the cone if (children == null || children.Count == 0) { throw new ArgumentNullException("children"); } this.Height = height; this.Name = name; this.Children = children; //create the cone if (tessellation < 3) { throw new ArgumentOutOfRangeException("tessellation"); } //Create a ring of triangels around the outside of the cones bottom for (int i = 0; i < tessellation; i++) { Vector3 normal = this.GetCircleVector(i, tessellation); // add the vertices for the top of the cone base.AddVertex(Vector3.Up * height, normal); //add the bottom circle base.AddVertex(normal * this.radius + Vector3.Down * height, normal); //Add indices base.AddIndex(i * 2); base.AddIndex(i * 2 + 1); base.AddIndex((i * 2 + 2) % (tessellation * 2)); base.AddIndex(i * 2 + 1); base.AddIndex((i * 2 + 3) % (tessellation * 2)); base.AddIndex((i * 2 + 2) % (tessellation * 2)); } //create flate triangle to seal the bottom this.CreateCap(tessellation, height, this.Radius, Vector3.Down); base.InitializePrimitive(device); } Sphere public void Initialize(GraphicsDevice device, Vector3 qi) { int verticalSegments = this.Tesselation; int horizontalSegments = this.Tesselation * 2; //single vertex on the bottom base.AddVertex((qi * this.Radius) + this.lowering, Vector3.Down); for (int i = 0; i < verticalSegments; i++) { float latitude = ((i + 1) * MathHelper.Pi / verticalSegments) - MathHelper.PiOver2; float dy = (float)Math.Sin(latitude); float dxz = (float)Math.Cos(latitude); //Create a singe ring of latitudes for (int j = 0; j < horizontalSegments; j++) { float longitude = j * MathHelper.TwoPi / horizontalSegments; float dx = (float)Math.Cos(longitude) * dxz; float dz = (float)Math.Sin(longitude) * dxz; Vector3 normal = new Vector3(dx, dy, dz); base.AddVertex(normal * this.Radius, normal); } } // Finish with a single vertex at the top of the sphere. AddVertex((qi * this.Radius) + this.lowering, Vector3.Up); // Create a fan connecting the bottom vertex to the bottom latitude ring. for (int i = 0; i < horizontalSegments; i++) { AddIndex(0); AddIndex(1 + (i + 1) % horizontalSegments); AddIndex(1 + i); } // Fill the sphere body with triangles joining each pair of latitude rings. for (int i = 0; i < verticalSegments - 2; i++) { for (int j = 0; j < horizontalSegments; j++) { int nextI = i + 1; int nextJ = (j + 1) % horizontalSegments; base.AddIndex(1 + i * horizontalSegments + j); base.AddIndex(1 + i * horizontalSegments + nextJ); base.AddIndex(1 + nextI * horizontalSegments + j); base.AddIndex(1 + i * horizontalSegments + nextJ); base.AddIndex(1 + nextI * horizontalSegments + nextJ); base.AddIndex(1 + nextI * horizontalSegments + j); } } // Create a fan connecting the top vertex to the top latitude ring. for (int i = 0; i < horizontalSegments; i++) { base.AddIndex(CurrentVertex - 1); base.AddIndex(CurrentVertex - 2 - (i + 1) % horizontalSegments); base.AddIndex(CurrentVertex - 2 - i); } base.InitializePrimitive(device); } The tricky part now is to arrange the spheres at the bottom of the cone. I tried is to draw just the cone and then draw the spheres. I need a lot of these cones, so it would be pretty hard to calculate all the positions correctly. Second Attempt So the second try was to generate a object that builds all vertices of the cone and all of the spheres at once. So I was hoping to render a cone with all its spheres arranged correctly. After a short debug I found out that the cone is created and the first sphere, when it turn of the second sphere I am running into an OutOfBoundsException of ushort.MaxValue. Cone and Spheres public ConeWithSpheres(GraphicsDevice device, float height, float coneDiameter, float sphereDiameter, int coneTessellation, int sphereTessellation, int numberOfSpheres) { if (coneTessellation < 3) { throw new ArgumentException(string.Format("{0} is to small for the tessellation of the cone. The number must be greater or equal to 3", coneTessellation)); } if (sphereTessellation < 3) { throw new ArgumentException(string.Format("{0} is to small for the tessellation of the sphere. The number must be greater or equal to 3", sphereTessellation)); } //set properties this.Height = height; this.ConeDiameter = coneDiameter; this.SphereDiameter = sphereDiameter; this.NumberOfChildren = numberOfSpheres; //end set properties //generate the cone this.GenerateCone(device, coneTessellation); //generate the spheres //vector that defines the Y position of the sphere on the cones bottom Vector3 lowering = new Vector3(0, 0.888f, 0); this.GenerateSpheres(device, sphereTessellation, numberOfSpheres, lowering); } // ------ GENERATE CONE ------ private void GenerateCone(GraphicsDevice device, int coneTessellation) { int doubleTessellation = coneTessellation * 2; //Create a ring of triangels around the outside of the cones bottom for (int index = 0; index < coneTessellation; index++) { Vector3 normal = this.GetCircleVector(index, coneTessellation); //add the vertices for the top of the cone base.AddVertex(Vector3.Up * this.Height, normal); //add the bottom of the cone base.AddVertex(normal * this.ConeRadius + Vector3.Down * this.Height, normal); //add indices base.AddIndex(index * 2); base.AddIndex(index * 2 + 1); base.AddIndex((index * 2 + 2) % doubleTessellation); base.AddIndex(index * 2 + 1); base.AddIndex((index * 2 + 3) % doubleTessellation); base.AddIndex((index * 2 + 2) % doubleTessellation); } //create flate triangle to seal the bottom this.CreateCap(coneTessellation, this.Height, this.ConeRadius, Vector3.Down); base.InitializePrimitive(device); } // ------ GENERATE SPHERES ------ private void GenerateSpheres(GraphicsDevice device, int sphereTessellation, int numberOfSpheres, Vector3 lowering) { int verticalSegments = sphereTessellation; int horizontalSegments = sphereTessellation * 2; for (int childCount = 1; childCount < numberOfSpheres; childCount++) { //single vertex at the bottom of the sphere base.AddVertex((this.GetCircleVector(childCount, this.NumberOfChildren) * this.SphereRadius) + lowering, Vector3.Down); for (int verticalSegmentsCount = 0; verticalSegmentsCount < verticalSegments; verticalSegmentsCount++) { float latitude = ((verticalSegmentsCount + 1) * MathHelper.Pi / verticalSegments) - MathHelper.PiOver2; float dy = (float)Math.Sin(latitude); float dxz = (float)Math.Cos(latitude); //create a single ring of latitudes for (int horizontalSegmentsCount = 0; horizontalSegmentsCount < horizontalSegments; horizontalSegmentsCount++) { float longitude = horizontalSegmentsCount * MathHelper.TwoPi / horizontalSegments; float dx = (float)Math.Cos(longitude) * dxz; float dz = (float)Math.Sin(longitude) * dxz; Vector3 normal = new Vector3(dx, dy, dz); base.AddVertex((normal * this.SphereRadius) + lowering, normal); } } //finish with a single vertex at the top of the sphere base.AddVertex((this.GetCircleVector(childCount, this.NumberOfChildren) * this.SphereRadius) + lowering, Vector3.Up); //create a fan connecting the bottom vertex to the bottom latitude ring for (int i = 0; i < horizontalSegments; i++) { base.AddIndex(0); base.AddIndex(1 + (i + 1) % horizontalSegments); base.AddIndex(1 + i); } //Fill the sphere body with triangles joining each pair of latitude rings for (int i = 0; i < verticalSegments - 2; i++) { for (int j = 0; j < horizontalSegments; j++) { int nextI = i + 1; int nextJ = (j + 1) % horizontalSegments; base.AddIndex(1 + i * horizontalSegments + j); base.AddIndex(1 + i * horizontalSegments + nextJ); base.AddIndex(1 + nextI * horizontalSegments + j); base.AddIndex(1 + i * horizontalSegments + nextJ); base.AddIndex(1 + nextI * horizontalSegments + nextJ); base.AddIndex(1 + nextI * horizontalSegments + j); } } //create a fan connecting the top vertiex to the top latitude for (int i = 0; i < horizontalSegments; i++) { base.AddIndex(this.CurrentVertex - 1); base.AddIndex(this.CurrentVertex - 2 - (i + 1) % horizontalSegments); base.AddIndex(this.CurrentVertex - 2 - i); } base.InitializePrimitive(device); } } Any ideas how I could fix this?

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• Nothing drawing on screen OpenGL with GLSL

  - by codemonkey

  I hate to be asking this kind of question here, but I am at a complete loss as to what is going wrong, so please bear with me. I am trying to render a single cube (voxel) in the center of the screen, through OpenGL with GLSL on Mac I begin by setting up everything using glut glutInit(&argc, argv); glutInitDisplayMode(GLUT_RGBA|GLUT_ALPHA|GLUT_DOUBLE|GLUT_DEPTH); glutInitWindowSize(DEFAULT_WINDOW_WIDTH, DEFAULT_WINDOW_HEIGHT); glutCreateWindow("Cubez-OSX"); glutReshapeFunc(reshape); glutDisplayFunc(render); glutIdleFunc(idle); _electricSheepEngine=new ElectricSheepEngine(DEFAULT_WINDOW_WIDTH, DEFAULT_WINDOW_HEIGHT); _electricSheepEngine->initWorld(); glutMainLoop(); Then inside the engine init camera & projection matrices: cameraPosition=glm::vec3(2,2,2); cameraTarget=glm::vec3(0,0,0); cameraUp=glm::vec3(0,0,1); glm::vec3 cameraDirection=glm::normalize(cameraPosition-cameraTarget); cameraRight=glm::cross(cameraDirection, cameraUp); cameraRight.z=0; view=glm::lookAt(cameraPosition, cameraTarget, cameraUp); lensAngle=45.0f; aspectRatio=1.0*(windowWidth/windowHeight); nearClippingPlane=0.1f; farClippingPlane=100.0f; projection=glm::perspective(lensAngle, aspectRatio, nearClippingPlane, farClippingPlane); then init shaders and check compilation and bound attributes & uniforms to be correctly bound (my previous question) These are my two shaders, vertex: #version 120 attribute vec3 position; attribute vec3 inColor; uniform mat4 mvp; varying vec3 fragColor; void main(void){ fragColor = inColor; gl_Position = mvp * vec4(position, 1.0); } and fragment: #version 120 varying vec3 fragColor; void main(void) { gl_FragColor = vec4(fragColor,1.0); } init the cube: setPosition(glm::vec3(0,0,0)); struct voxelData data[]={ //front face {{-1.0, -1.0, 1.0}, {0.0, 0.0, 1.0}}, {{ 1.0, -1.0, 1.0}, {0.0, 1.0, 1.0}}, {{ 1.0, 1.0, 1.0}, {0.0, 0.0, 1.0}}, {{-1.0, 1.0, 1.0}, {0.0, 1.0, 1.0}}, //back face {{-1.0, -1.0, -1.0}, {0.0, 0.0, 1.0}}, {{ 1.0, -1.0, -1.0}, {0.0, 1.0, 1.0}}, {{ 1.0, 1.0, -1.0}, {0.0, 0.0, 1.0}}, {{-1.0, 1.0, -1.0}, {0.0, 1.0, 1.0}} }; glGenBuffers(1, &modelVerticesBufferObject); glBindBuffer(GL_ARRAY_BUFFER, modelVerticesBufferObject); glBufferData(GL_ARRAY_BUFFER, sizeof(data), data, GL_STATIC_DRAW); glBindBuffer(GL_ARRAY_BUFFER, 0); const GLubyte indices[] = { // Front 0, 1, 2, 2, 3, 0, // Back 4, 6, 5, 4, 7, 6, // Left 2, 7, 3, 7, 6, 2, // Right 0, 4, 1, 4, 1, 5, // Top 6, 2, 1, 1, 6, 5, // Bottom 0, 3, 7, 0, 7, 4 }; glGenBuffers(1, &modelFacesBufferObject); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, modelFacesBufferObject); glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0); and then the render call: glClearColor(0.52, 0.8, 0.97, 1.0); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glEnable(GL_DEPTH_TEST); //use the shader glUseProgram(shaderProgram); //enable attributes in program glEnableVertexAttribArray(shaderAttribute_position); glEnableVertexAttribArray(shaderAttribute_color); //model matrix using model position vector glm::mat4 mvp=projection*view*voxel->getModelMatrix(); glUniformMatrix4fv(shaderAttribute_mvp, 1, GL_FALSE, glm::value_ptr(mvp)); glBindBuffer(GL_ARRAY_BUFFER, voxel->modelVerticesBufferObject); glVertexAttribPointer(shaderAttribute_position, // attribute 3, // number of elements per vertex, here (x,y) GL_FLOAT, // the type of each element GL_FALSE, // take our values as-is sizeof(struct voxelData), // coord every (sizeof) elements 0 // offset of first element ); glBindBuffer(GL_ARRAY_BUFFER, voxel->modelVerticesBufferObject); glVertexAttribPointer(shaderAttribute_color, // attribute 3, // number of colour elements per vertex, here (x,y) GL_FLOAT, // the type of each element GL_FALSE, // take our values as-is sizeof(struct voxelData), // coord every (sizeof) elements (GLvoid *)(offsetof(struct voxelData, color3D)) // offset of colour data ); //draw the model by going through its elements array glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, voxel->modelFacesBufferObject); int bufferSize; glGetBufferParameteriv(GL_ELEMENT_ARRAY_BUFFER, GL_BUFFER_SIZE, &bufferSize); glDrawElements(GL_TRIANGLES, bufferSize/sizeof(GLushort), GL_UNSIGNED_SHORT, 0); //close up the attribute in program, no more need glDisableVertexAttribArray(shaderAttribute_position); glDisableVertexAttribArray(shaderAttribute_color); but on screen all I get is the clear color :$ I generate my model matrix using: modelMatrix=glm::translate(glm::mat4(1.0), position); which in debug turns out to be for the position of (0,0,0): |1, 0, 0, 0| |0, 1, 0, 0| |0, 0, 1, 0| |0, 0, 0, 1| Sorry for such a question, I know it is annoying to look at someone's code, but I promise I have tried to debug around and figure it out as much as I can, and can't come to a solution Help a noob please? EDIT: Full source here, if anyone wants

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• Good book or tutorial for learning how to apply integration methods

  - by Cumatru

  I'm looking to animate a graph layout using edges as springs and nodes as weights ( a node with more links will have a bigger weight ). I'm not capable of wrapping my head around the usage of mathematical and physics relations in my application. As far as i read, Runge Kutta 4 ( preferably ) or Verlet will be a good choice, but i have problems with understanding how they really work, and what physics equations should i apply. If i can't understand them, i can't use them. I'm looking for a book or a tutorial which describe the things that i need.

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• Double sides face with two normals

  - by Marnix

  I think this isn't possible, but I just want to check this: Is it possible to create a face in opengl that has two normals? So: I want the inside and outside of some cilinder to be drawn, but I want the lights to do as expected and not calculate it for the normal given. I was trying to do this with backface culling off, so I would have both faces, but the light was wrongly calculated of course. Is this possible, or do I have to draw an inside and an outside? So draw twice?

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• Why does glGetString returns a NULL string

  - by snape

  I am trying my hands at GLFW library. I have written a basic program to get OpenGL renderer and vendor string. Here is the code #include <GL/glew.h> #include <GL/glfw.h> #include <cstdio> #include <cstdlib> #include <string> using namespace std; void shutDown(int returnCode) { printf("There was an error in running the code with error %d\n",returnCode); GLenum res = glGetError(); const GLubyte *errString = gluErrorString(res); printf("Error is %s\n", errString); glfwTerminate(); exit(returnCode); } int main() { // start GL context and O/S window using GLFW helper library if (glfwInit() != GL_TRUE) shutDown(1); if (glfwOpenWindow(0, 0, 0, 0, 0, 0, 0, 0, GLFW_WINDOW) != GL_TRUE) shutDown(2); // start GLEW extension handler glewInit(); // get version info const GLubyte* renderer = glGetString (GL_RENDERER); // get renderer string const GLubyte* version = glGetString (GL_VERSION); // version as a string printf("Renderer: %s\n", renderer); printf("OpenGL version supported %s\n", version); // close GL context and any other GLFW resources glfwTerminate(); return 0; } I googled this error and found out that we have to initialize the OpenGL context before calling glGetString(). Although I have initialized OpenGL context using glfwInit() but still the function returns a NULL string. Any ideas? Edit I have updated the code with error checking mechanisms. This code on running outputs the following There was an error in running the code with error 2 Error is no error

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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 to fix bad Collada produced by FBX?

  - by David

  I tried to use the FBX SDK (2011.3.1) to load FBX files and save them as Collada files in order to be able to import FBX files in Panda3D. Unfortunately the resulting Collada files are not usable for several reasons, among them: There's a Maya specific extra technique diffuse <diffuse> <texture texture="Map__2-image" texcoord="CHANNEL0"> <extra> <technique profile="MAYA"> <wrapU sid="wrapU0">TRUE</wrapU> <wrapV sid="wrapV0">TRUE</wrapV> <blend_mode>ADD</blend_mode> </technique> </extra> </texture> </diffuse> It assigns a texcoord channel name that isn't referenced anywhere else in the file (in the previous code sample, no geometry uses "CHANNEL0"...) Every polygon is exported twice, a first time with a basic material (only diffuse color, specular color, etc.) and a second time with a textured material -- this doubles the number of polygons of each model without any valuable reason Anyway, the resulting Collada file cannot be opened correctly either with OpenCOLLADA or Panda3D's "dae2egg". Anyone has any experience on how to "fix" it and make it understandable by common and well-reputed Collada importers such as OpenCOLLADA?

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• Largest sphere inside a frustum

  - by Will

  How do you find the largest sphere that you can draw in perspective? Viewed from the top, it'd be this: Added: on the frustum on the right, I've marked four points I think we know something about. We can unproject all eight corners of the frusum, and the centres of the near and far ends. So we know point 1, 3 and 4. We also know that point 2 is the same distance from 3 as 4 is from 3. So then we can compute the nearest point on the line 1 to 4 to point 2 in order to get the centre? But the actual math and code escapes me. I want to draw models (which are approximately spherical and which I have a miniball bounding sphere for) as large as possible. Update: I've tried to implement the incircle-on-two-planes approach as suggested by bobobobo and Nathan Reed : function getFrustumsInsphere(viewport,invMvpMatrix) { var midX = viewport[0]+viewport[2]/2, midY = viewport[1]+viewport[3]/2, centre = unproject(midX,midY,null,null,viewport,invMvpMatrix), incircle = function(a,b) { var c = ray_ray_closest_point_3(a,b); a = a[1]; // far clip plane b = b[1]; // far clip plane c = c[1]; // camera var A = vec3_length(vec3_sub(b,c)), B = vec3_length(vec3_sub(a,c)), C = vec3_length(vec3_sub(a,b)), P = 1/(A+B+C), x = ((A*a[0])+(B*a[1])+(C*a[2]))*P, y = ((A*b[0])+(B*b[1])+(C*b[2]))*P, z = ((A*c[0])+(B*c[1])+(C*c[2]))*P; c = [x,y,z]; // now the centre of the incircle c.push(vec3_length(vec3_sub(centre[1],c))); // add its radius return c; }, left = unproject(viewport[0],midY,null,null,viewport,invMvpMatrix), right = unproject(viewport[2],midY,null,null,viewport,invMvpMatrix), horiz = incircle(left,right), top = unproject(midX,viewport[1],null,null,viewport,invMvpMatrix), bottom = unproject(midX,viewport[3],null,null,viewport,invMvpMatrix), vert = incircle(top,bottom); return horiz[3]<vert[3]? horiz: vert; } I admit I'm winging it; I'm trying to adapt 2D code by extending it into 3 dimensions. It doesn't compute the insphere correctly; the centre-point of the sphere seems to be on the line between the camera and the top-left each time, and its too big (or too close). Is there any obvious mistakes in my code? Does the approach, if fixed, work?

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