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• How do I make my rain effect look more like rain and less like snowfall?

  - by Nikhil Lamba

  I am making a game in that game I want a rain effect. I am little bit far from this right now. I am creating the rain effect like below: particleSystem.addParticleInitializer(new ColorInitializer(1, 1, 1)); particleSystem.addParticleInitializer(new AlphaInitializer(0)); particleSystem.setBlendFunction(GL10.GL_SRC_ALPHA, GL10.GL_ONE); particleSystem.addParticleInitializer(new VelocityInitializer(2, 2, 20, 10)); particleSystem.addParticleInitializer(new RotationInitializer(0.0f, 30.0f)); particleSystem.addParticleModifier(new ScaleModifier(1.0f, 2.0f, 0, 150)); particleSystem.addParticleModifier(new ColorModifier(1, 1, 1, 1f, 1, 1, 1, 3)); particleSystem.addParticleModifier(new ColorModifier(1, 1, 1f, 1, 1, 1, 1, 6)); particleSystem.addParticleModifier(new AlphaModifier(0, 1, 0, 3)); particleSystem.addParticleModifier(new AlphaModifier(1, 0, 1, 125)); particleSystem.addParticleModifier(new ExpireModifier(50, 50)); scene.attachChild(particleSystem); But it looks like snowfall! What changes can I do for it to look more like rain? EDIT Here is a screenshot:

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• Algorithm for waypoint path following?

  - by Thierry Savard Saucier

  I have a worldmap, with different cities on it. The player can choose a city from a menu, or click on an available cities on the world map, and the toon should walk over there. I want him to follow a predefined path. Lets say our hero is on the city 1. He clicks on city 4. I want him to follow the path to city 2 and from there to city 4. I was handling this easily with arrow movement (left right top bottom) since its a single check. Now I'm not sure how I should do this. Should I loop threw each possible path and check which one leads me to D the fastest ... and if I do how do I avoid running in circle forever with cities 1-5-2 ?

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• Cool examples of procedural pixel shader effects?

  - by Robert Fraser

  What are some good examples of procedural/screen-space pixel shader effects? No code necessary; just looking for inspiration. In particular, I'm looking for effects that are not dependent on geometry or the rest of the scene (would look okay rendered alone on a quad) and are not image processing (don't require a "base image", though they can incorporate textures). Multi-pass or single-pass is fine. Screenshots or videos would be ideal, but ideas work too. Here are a few examples of what I'm looking for (all from the RenderMonkey samples): PS - I'm aware of this question; I'm not asking for a source of actual shader implementations but instead for some inspirational ideas -- and the ones at the NVIDIA Shader Library mostly require a scene or are image processing effects. EDIT: this is an open-ended question and I wish there was a good way to split the bounty. I'll award the rep to the best answer on the last day.

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• GLM Velocity Vectors - Basic Maths to Simulate Steering

  - by Reanimation

  UPDATE - Code updated below but still need help adjusting my math. I have a cube rendered on the screen which represents a car (or similar). Using Projection/Model matrices and Glm I am able to move it back and fourth along the axes and rotate it left or right. I'm having trouble with the vector mathematics to make the cube move forwards no matter which direction it's current orientation is. (ie. if I would like, if it's rotated right 30degrees, when it's move forwards, it travels along the 30degree angle on a new axes). I hope I've explained that correctly. This is what I've managed to do so far in terms of using glm to move the cube: glm::vec3 vel; //velocity vector void renderMovingCube(){ glUseProgram(movingCubeShader.handle()); GLuint matrixLoc4MovingCube = glGetUniformLocation(movingCubeShader.handle(), "ProjectionMatrix"); glUniformMatrix4fv(matrixLoc4MovingCube, 1, GL_FALSE, &ProjectionMatrix[0][0]); glm::mat4 viewMatrixMovingCube; viewMatrixMovingCube = glm::lookAt(camOrigin, camLookingAt, camNormalXYZ); vel.x = cos(rotX); vel.y=sin(rotX); vel*=moveCube; //move cube ModelViewMatrix = glm::translate(viewMatrixMovingCube,globalPos*vel); //bring ground and cube to bottom of screen ModelViewMatrix = glm::translate(ModelViewMatrix, glm::vec3(0,-48,0)); ModelViewMatrix = glm::rotate(ModelViewMatrix, rotX, glm::vec3(0,1,0)); //manually turn glUniformMatrix4fv(glGetUniformLocation(movingCubeShader.handle(), "ModelViewMatrix"), 1, GL_FALSE, &ModelViewMatrix[0][0]); //pass matrix to shader movingCube.render(); //draw glUseProgram(0); } keyboard input: void keyboard() { char BACKWARD = keys['S']; char FORWARD = keys['W']; char ROT_LEFT = keys['A']; char ROT_RIGHT = keys['D']; if (FORWARD) //W - move forwards { globalPos += vel; //globalPos.z -= moveCube; BACKWARD = false; } if (BACKWARD)//S - move backwards { globalPos.z += moveCube; FORWARD = false; } if (ROT_LEFT)//A - turn left { rotX +=0.01f; ROT_LEFT = false; } if (ROT_RIGHT)//D - turn right { rotX -=0.01f; ROT_RIGHT = false; } Where am I going wrong with my vectors? I would like change the direction of the cube (which it does) but then move forwards in that direction.

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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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• GameState management hierarchical FSM vs stack based FSM

  - by user8363

  I'm reading a bit on Finite State Machines to handle game states (or screens). I would like to build a rather decent FSM that can handle multiple screens. e.g. while the game is running I want to be able to pop-up an ingame menu and when that happens the main screen must stop updating (the game is paused) but must still be visible in the background. However when I open an inventory pop-up the main screen must be visible and continue updating etc. I'm a bit confused about the difference in implementation and functionality between hierarchical FSM's and FSM's that handle a stack of states instead. Are they basically the same? Or are there important differences?

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• Normals vs Normal maps

  - by KaiserJohaan

  I am using Assimp asset importer (http://assimp.sourceforge.net/lib_html/index.html) to parse 3d models. So far, I've simply pulled out the normal vectors which are defined for each vertex in my meshes. Yet I have also found various tutorials on normal maps... As I understand it for normal maps, the normal vectors are stored in each texel of a normal map, and you pull these out of the normal texture in the shader. Why is there two ways to get the normals, which one is considered best-practice and why?

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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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• PCF shadow shader math causing artifacts

  - by user2971069

  For a while now I used PCSS for my shadow technique of choice until I discovered a type of percentage closer filtering. This method creates really smooth shadows and with hopes of improving performance, with only a fraction of texture samples, I tried to implement PCF into my shader. This is the relevant code: float c0, c1, c2, c3; float f = blurFactor; float2 coord = ProjectedTexCoords; if (receiverDistance - tex2D(lightSampler, coord + float2(0, 0)).x > 0.0007) c0 = 1; if (receiverDistance - tex2D(lightSampler, coord + float2(f, 0)).x > 0.0007) c1 = 1; if (receiverDistance - tex2D(lightSampler, coord + float2(0, f)).x > 0.0007) c2 = 1; if (receiverDistance - tex2D(lightSampler, coord + float2(f, f)).x > 0.0007) c3 = 1; coord = (coord % f) / f; return 1 - (c0 * (1 - coord.x) * (1 - coord.y) + c1 * coord.x * (1 - coord.y) + c2 * (1 - coord.x) * coord.y + c3 * coord.x * coord.y); This is a very basic implementation. blurFactor is initialized with 1 / LightTextureSize. So the if statements fetch the occlusion values for the four adjacent texels. I now want to weight each value based on the actual position of the texture coordinate. If it's near the bottom-right pixel, that occlusion value should be preferred. The weighting itself is done with a simple bilinear interpolation function, however this function takes a 2d vector in the range [0..1] so I have to convert my texture coordinate to get the distance from my first pixel to the second one in range [0..1]. For that I used the mod operator to get it into [0..f] range and then divided by f. This code makes sense to me, and for specific blurFactors it works, producing really smooth one pixel wide shadows, but not for all blurFactors. Initially blurFactor is (1 / LightTextureSize) to sample the 4 adjacent texels. I now want to increase the blurFactor by factor x to get a smooth interpolation across maybe 4 or so pixels. But that is when weird artifacts show up. Here is an image: Using a 1x on blurFactor produces a good result, 0.5 is as expected not so smooth. 2x however doesn't work at all. I found that only a factor of 1/2^n produces an good result, every other factor produces artifacts. I'm pretty sure the error lies here: coord = (coord % f) / f; Maybe the modulo is not calculated correctly? I have no idea how to fix that. Is it even possible for pixel that are further than 1 pixel away?

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• How to port animation from one skeleton to another?

  - by shawn

  While I need to do this in a Blender3D modeler script, the math should be similar for other modelers or realtime engines. Blender3D specific terminology: Armature = skeleton EditBone = rest pose bone (stores the rest pose matrix) PoseBone = can store a different pose (animation matrix) for each frame of your animation I need to share animations (Blender Actions) between Armatures which have EditBones with same names and which have the same positions, but can have different (rest pose) angles and scales. Plus the Armatures might have different bone hierarchy (bone parenting/ no bone parenting). Why I need this: I've made an importer/exporter for a 3d format for a game. The format doesn't store enough info to connect/parent the bones, which makes posing/animating character models in a 3d modeller nearly impossible (original model files for the 3d modeler don't exist, this is for modding). As there are only 2 character skeleton types in the game, I decided to optionally allow to generate the bone from a hardcoded data in the model importer and undo that in the exporter. This allows to easily pose the model for checking weights, easily create weights, makes it easier for Blender to generate automatic weights and of course makes animating possible. This worked perfectly: the importer optionally generated the Armature itself and the exporter removed those changes, so the exported model works with existing animations in the game. But now I'm writing an importer and exporter for the game's animation format and here come the problems of: Trying to make original animations work in Blender with my "custom" (modified) Armature Trying to make animations created by using the "custom" (modified) Armature work with the original models in the game (and Blender). Constraints or bone snapping inside Blender won't work as they don't care that the bones have different angles in the rest pose, they will still face the same direction. It seems I just need to get the "difference" between the EditBone matrices of all EditBones for the two Armatures somehow and apply that difference to PoseBone matrices of all PoseBones, for all frames of my animation. I need to know how to get that difference and how to apply it. BTW, PoseBone matrices are relative to rest pose, they are by default [1.000000, 0.000000, 0.000000, 0.000000](matrix [row 0]) [0.000000, 1.000000, 0.000000, 0.000000](matrix [row 1]) [0.000000, 0.000000, 1.000000, 0.000000](matrix [row 2]) [0.000000, 0.000000, 0.000000, 1.000000](matrix [row 3]) So the question is: How to get the difference between two bone (EditBone) matrices to apply that difference to the animation matrices (PoseBone matrices)? Please be easy on the matrix math.

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• GetData() error creating framebuffer

  - by Lelezeus

  I'm currently porting a game written in C# with XNA library to Android with Monogame. I have a Texture2D and i'm trying to get an array of uint in this way: Texture2d textureDeform = game.Content.Load<Texture2D>("Texture/terrain"); uint[] pixelDeformData = new uint[textureDeform.Width * textureDeform.Height]; textureDeform.GetData(pixelDeformData, 0, textureDeform.Width * textureDeform.Height); I get the following exception: System.Exception: Error creating framebuffer: Zero at Microsoft.Xna.Framework.Graphics.Texture2D.GetTextureData (Int32 ThreadPriorityLevel) [0x00000] in :0 I found that the problem is in private byte[] GetTextureData(int ThreadPriorityLevel) creating the framebuffer: private byte[] GetTextureData(int ThreadPriorityLevel) { int framebufferId = -1; int renderBufferID = -1; GL.GenFramebuffers(1, ref framebufferId); // framebufferId is still -1 , why can't be created? GraphicsExtensions.CheckGLError(); GL.BindFramebuffer(All.Framebuffer, framebufferId); GraphicsExtensions.CheckGLError(); //renderBufferIDs = new int[currentRenderTargets]; GL.GenRenderbuffers(1, ref renderBufferID); GraphicsExtensions.CheckGLError(); // attach the texture to FBO color attachment point GL.FramebufferTexture2D(All.Framebuffer, All.ColorAttachment0, All.Texture2D, this.glTexture, 0); GraphicsExtensions.CheckGLError(); // create a renderbuffer object to store depth info GL.BindRenderbuffer(All.Renderbuffer, renderBufferID); GraphicsExtensions.CheckGLError(); GL.RenderbufferStorage(All.Renderbuffer, All.DepthComponent24Oes, Width, Height); GraphicsExtensions.CheckGLError(); // attach the renderbuffer to depth attachment point GL.FramebufferRenderbuffer(All.Framebuffer, All.DepthAttachment, All.Renderbuffer, renderBufferID); GraphicsExtensions.CheckGLError(); All status = GL.CheckFramebufferStatus(All.Framebuffer); if (status != All.FramebufferComplete) throw new Exception("Error creating framebuffer: " + status); ... } The frameBufferId is still -1, seems that framebuffer could not be generated and I don't know why. Any help would be appreciated, thank you in advance.

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• Coarse Collision Detection in highly dynamic environment

  - by Millianz

  I'm currently working a 3D space game with A LOT of dynamic objects that are all moving (there is pretty much no static environment). I have the collision detection and resolution working just fine, but I am now trying to optimize the collision detection (which is currently O(N^2) -- linear search). I thought about multiple options, a bounding volume hierarchy, a Binary Spatial Partitioning tree, an Octree or a Grid. I however need some help with deciding what's best for my situation. A grid seems unfeasible simply due to the space requirements and cache coherence problems. Since everything is so dynamic however, it seems to be that trees aren't ideal either, since they would have to be completely rebuilt every frame. I must admit I never implemented a physics engine that required spatial partitioning, do I indeed need to rebuild the tree every frame (assuming that everything is constantly moving) or can I update the trees after integrating? Advice is much appreciated - to give some more background: You're flying a space ship in an asteroid field, and there are lots and lots of asteroids and some enemy ships, all of which shoot bullets. EDIT: I came across the "Sweep an Prune" algorithm, which seems like the right thing for my purposes. It appears like the right mixture of fast building of the data structures involved and detailed enough partitioning. This is the best resource I can find: http://www.codercorner.com/SAP.pdf If anyone has any suggestions whether or not I'm going in the right direction, please let me know.

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• Problem with Assimp 3D model loader

  - by Brendan Webster

  In my game I have model loading functions for Assimp model loading library. I can load the model and render it, but the model displays incorrectly. The models load in as if they were using a seperate projection matrix. I have looked over my code over and over again, but I probably keep on missing the obvious reason why this is happening. Here is an image of my game: It's simply a 6 sided cube, but it's off big time! Here are my code snippets for rendering the cube to the screen: void C_MediaLoader::display(void) { float tmp; glTranslatef(0,0,0); // rotate it around the y axis glRotatef(angle,0.f,0.f,1.f); glColor4f(1,1,1,1); // scale the whole asset to fit into our view frustum tmp = scene_max.x-scene_min.x; tmp = aisgl_max(scene_max.y - scene_min.y,tmp); tmp = aisgl_max(scene_max.z - scene_min.z,tmp); tmp = (1.f / tmp); glScalef(tmp/5, tmp/5, tmp/5); // center the model //glTranslatef( -scene_center.x, -scene_center.y, -scene_center.z ); // if the display list has not been made yet, create a new one and // fill it with scene contents if(scene_list == 0) { scene_list = glGenLists(1); glNewList(scene_list, GL_COMPILE); // now begin at the root node of the imported data and traverse // the scenegraph by multiplying subsequent local transforms // together on GL's matrix stack. recursive_render(scene, scene->mRootNode); glEndList(); } glCallList(scene_list); } void C_MediaLoader::recursive_render (const struct aiScene *sc, const struct aiNode* nd) { unsigned int i; unsigned int n = 0, t; struct aiMatrix4x4 m = nd->mTransformation; // update transform aiTransposeMatrix4(&m); glPushMatrix(); glMultMatrixf((float*)&m); // draw all meshes assigned to this node for (; n < nd->mNumMeshes; ++n) { const struct aiMesh* mesh = scene->mMeshes[nd->mMeshes[n]]; apply_material(sc->mMaterials[mesh->mMaterialIndex]); if(mesh->mNormals == NULL) { glDisable(GL_LIGHTING); } else { glEnable(GL_LIGHTING); } for (t = 0; t < mesh->mNumFaces; ++t) { const struct aiFace* face = &mesh->mFaces[t]; GLenum face_mode; switch(face->mNumIndices) { case 1: face_mode = GL_POINTS; break; case 2: face_mode = GL_LINES; break; case 3: face_mode = GL_TRIANGLES; break; default: face_mode = GL_POLYGON; break; } glBegin(face_mode); for(i = 0; i < face->mNumIndices; i++) { int index = face->mIndices[i]; if(mesh->mColors[0] != NULL) glColor4fv((GLfloat*)&mesh->mColors[0][index]); if(mesh->mNormals != NULL) glNormal3fv(&mesh->mNormals[index].x); glVertex3fv(&mesh->mVertices[index].x); } glEnd(); } } // draw all children for (n = 0; n < nd->mNumChildren; ++n) { recursive_render(sc, nd->mChildren[n]); } glPopMatrix(); } Sorry there is so much code to look through, but I really cannot find the problem, and I would love to have help.

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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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• Client side latency when using prediction

  - by Tips48

  I've implemented Client-Side prediction into my game, where when input is received by the client, it first sends it to the server and then acts upon it just as the server will, to reduce the appearance of lag. The problem is, the server is authoritative, so when the server sends back the position of the Entity to the client, it undo's the effect of the interpolation and creates a rubber-banding effect. For example: Client sends input to server - Client reacts on input - Server receives and reacts on input - Server sends back response - Client reaction is undone due to latency between server and client To solve this, I've decided to store the game state and input every tick in the client, and then when I receive a packet from the server, get the game state from when the packet was sent and simulate the game up to the current point. My questions: Won't this cause lag? If I'm receiving 20/30 EntityPositionPackets a second, that means I have to run 20-30 simulations of the game state. How do I sync the client and server tick? Currently, I'm sending the milli-second the packet was sent by the server, but I think it's adding too much complexity instead of just sending the tick. The problem with converting it to sending the tick is that I have no guarantee that the client and server are ticking at the same rate, for example if the client is an old-end PC.

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• Sprite not rotating around its centre after Scaling at its centre

  - by asma.farhat

  If I scale a sprite at its centre, then try to rotate it around its centre as well, the rotation does not occur around its centre. If you need to rotate, for example a scaled ball,the way its working it is set the scale center at the top left (0,0) set the scale that you want, and then set the rotation center to the middle of the scaled sprite, and then apply the rotation modifier. blaBloBliSprite.setScaleCenter(0, 0); blaBloBliSprite.setScale(0.667f); blaBloBliSprite.setPosition(557, CAMERA_HEIGHT / 2 - blaBloBliSprite.getHeightScaled() / 2); blaBloBliSprite.setRotationCenter(blaBloBliSprite.getWidthScaled() / 2, blaBloBliSprite.getHeightScaled() / 2); But I want to scale a sprite at its centre as well. Is there any way of doing it?

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• Handling packet impersonating in client-server model online game

  - by TheDespite

  I am designing a server-client model game library/engine. How do I, and should I even bother to handle frequent update packet possible impersonating? In my current design anyone could copy a packet from someone else and modify it to execute any non-critical action for another client. I am currently compressing all datagrams so that adds just a tad of security. Edit: One way I thought about was to send a unique "key" to the verified client every x_time and then the client has to add that to all of it's update packets until a new key is sent. Edit2: I should have mentioned that I am not concerned about whether the actions described in the packet are available to the client at the time, this is all checked by the server which I thought was obvious. I am only concerned about someone sending packets for another client.

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• Map building - Tower Defense

  - by Dan K

  Before diving too deep into my question, let it be known that I am learning as far as java script goes and figured a simple Tower Defense game would be an excellent way to learn things. So I have found a simple background image with a path drawn on it and my question is how would I go about building a path so that I can animate my objects. Would I have to take the image and overlay a grid system, or can I store the path in some sort of array and have my objects move across it? Here is the background image:

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• how to link a c++ object to a local variable in Lua

  - by MahanGM

  I'm completing my scripting interface with Lua, but recently I've stuck at some point. I have several functions for my Entitiy events like Update(). I have a function called create_entitiy() which instantiate a new entity from a given entity index: function Update() local bullet = create_entity(0, 0, "obj_bullet") end create_entity returns a table which is the properties of the created entity. Now how can I make a connection between bullet variable and my newly created object? Right now for previously added objects to the scene, I simply set a global table for each of them and then after every call to Update(), I go through registered names to find object tables and perform new changes. Like the one below: function Update() if keyboard_key_press(vk_right) then obj_player.x += 3 end I can get obj_player table because I know its name from C++, plus I can get it as a global table and simply reach for the first instance named obj_player. Is there any solution for me to make bullet variable act like this? I was thinking to get all local variables in Update() function and check for every one to see if is it table and it has an unique field attached to it like id, this way I can determine that this is an object table and do the rest of the process. By the way, is this interface going to work easier with luaBind if I implement it? Bottom line: How can I make a local variable in Lua that receives a table from create_entity function and track that local variable to capture it from C++. e. g. function Update() local bullet = create_entity(0, 0, "obj_bullet") bullet.x = 10 <== Commit a change in table end Now I want to get variable bullet from C++. And it's not just this variable, there might be a ton of these local variables with different names.

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• Calculating instantaneous speed and acceleration for a simple Car software model

  - by Dylan

  I am trying to model a speedometer and tachometer for a simple software model of a car dashboard. I want this to be relatively simple, so for my purposes I won't likely simulate variables such as drag (or, assume that drag is a constant). But I would like to know the general formulas for: 1) Calculating the RPM, depending on a position of a graphical slider representing the accelerator. 2) Using this information to find the instantaneous speed (or, magnitude of instantaneous velocity?). I am not sure, in the case of 2), what other independent variables I need to consider. Do I need to consider the frequency of rotation of the wheels (assuming a fixed radius), in addition to the RPM? If anyone can give me a rough explanation plus relevant formulas, or alternatively direct me to other trusted resources online (I have had a hard time sifting through info and determining the accuracy), it would be much appreciated.

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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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• Trying to setup first DirectX project (don't understand the error) [on hold]

  - by user1157885

  I've just started learning DirectX with the book "3D Game Programming with DirectX". I just finished setting up all the paths and adding the code to the project which I think I did correctly, but I get this massive error which I don't really understand and is hard to google. Could someone tell me what it means and how to fix it? Error 1 error TRK0002: Failed to execute command: ""C:\Program Files (x86)\Microsoft DirectX SDK (June 2010)\Utilities\bin\x64\fxc.exe" /nologo /Emain /Fo "C:\Desktop\DirectX 11 Projects\box\Win32Project2\Debug\color.cso" /Od /Zi "....\Book Files\3DGameProg\DVD\Code\Chapter 6 Drawing in Direct3D\Box\FX\color.fx"". The handle is invalid.

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• Logarithmic spacing of FFT bins

  - by Mykel Stone

  I'm trying to do the examples within the GameDev.net Beat Detection article ( http://archive.gamedev.net/archive/reference/programming/features/beatdetection/index.html ) I have no issue with performing a FFT and getting the frequency data and doing most of the article. I'm running into trouble though in the section 2.B, Enhancements and beat decision factors. in this section the author gives 3 equations numbered R10-R12 to be used to determine how many bins go into each subband: R10 - Linear increase of the width of the subband with its index R11 - We can choose for example the width of the first subband R12 - The sum of all the widths must not exceed 1024 He says the following in the article: "Once you have equations (R11) and (R12) it is fairly easy to extract 'a' and 'b', and thus to find the law of the 'wi'. This calculus of 'a' and 'b' must be made manually and 'a' and 'b' defined as constants in the source; indeed they do not vary during the song." However, I cannot seem to understand how these values are calculated...I'm probably missing something simple, but learning fourier analysis in a couple of weeks has left me Decimated-in-Mind and I cannot seem to see it.

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• How to fetch only the sprites in the player's range of motion for collision testing? (2D, axis aligned sprites)

  - by Twodordan

  I am working on a 2D sprite game for educational purposes. (In case you want to know, it uses WebGl and Javascript) I've implemented movement using the Euler method (and delta time) to keep things simple. Now I'm trying to tackle collisions. The way I wrote things, my game only has rectangular sprites (axis aligned, never rotated) of various/variable sizes. So I need to figure out what I hit and which side of the target sprite I hit (and I'm probably going to use these intersection tests). The old fashioned method seems to be to use tile based grids, to target only a few tiles at a time, but that sounds silly and impractical for my game. (Splitting the whole level into blocks, having each sprite's bounding box fit multiple blocks I might abide. But if the sprites change size and move around, you have to keep changing which tiles they belong to, every frame, it doesn't sound right.) In Flash you can test collision under one point, but it's not efficient to iterate through all the elements on stage each frame. (hence why people use the tile method). Bottom line is, I'm trying to figure out how to test only the elements within the player's range of motion. (I know how to get the range of motion, I have a good idea of how to write a collisionCheck(playerSprite, targetSprite) function. But how do I know which sprites are currently in the player's vicinity to fetch only them?) Please discuss. Cheers!

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• Open GL stars are not rendering

  - by Darestium

  I doing Nehe's Open GL Lesson 9. I'm using SFML for windowing, the strange thing is no stars are rendering. #include <SFML/System.hpp> #include <SFML/Window.hpp> #include <SFML/Graphics.hpp> #include <iostream> void processEvents(sf::Window *app); void processInput(sf::Window *app); void renderGlScene(sf::Window *app); void init(); int loadResources(); const int NUM_OF_STARS = 50; float triRot = 0.0f; float quadRot = 0.0f; bool twinkle = false; bool tKey = false; float zoom = 15.0f; float tilt = 90.0f; float spin = 0.0f; unsigned int loop; unsigned int texture_handle[1]; typedef struct { int r, g, b; float distance; float angle; } stars; stars star[NUM_OF_STARS]; int main() { sf::Window app(sf::VideoMode(800, 600, 32), "Nehe Lesson 9"); app.UseVerticalSync(false); init(); if (loadResources() == -1) { return EXIT_FAILURE; } while (app.IsOpened()) { processEvents(&app); processInput(&app); renderGlScene(&app); app.Display(); } return EXIT_SUCCESS; } int loadResources() { sf::Image img_data; // Load Texture if (!img_data.LoadFromFile("data/images/star.bmp")) { std::cout << "Could not load data/images/star.bmp"; return -1; } // Generate 1 texture glGenTextures(1, &texture_handle[0]); // Linear filtering glBindTexture(GL_TEXTURE_2D, texture_handle[0]); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, img_data.GetWidth(), img_data.GetHeight(), 0, GL_RGBA, GL_UNSIGNED_BYTE, img_data.GetPixelsPtr()); return 0; } void processInput(sf::Window *app) { const sf::Input& input = app->GetInput(); if (input.IsKeyDown(sf::Key::T) && !tKey) { tKey = true; twinkle = !twinkle; } if (!input.IsKeyDown(sf::Key::T)) { tKey = false; } if (input.IsKeyDown(sf::Key::Up)) { tilt -= 0.05f; } if (input.IsKeyDown(sf::Key::Down)) { tilt += 0.05f; } if (input.IsKeyDown(sf::Key::PageUp)) { zoom -= 0.02f; } if (input.IsKeyDown(sf::Key::Up)) { zoom += 0.02f; } } void init() { glClearDepth(1.f); glClearColor(0.f, 0.f, 0.f, 0.f); // Enable texturing glEnable(GL_TEXTURE_2D); //glDepthMask(GL_TRUE); // Setup a perpective projection glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluPerspective(45.f, 1.f, 1.f, 500.f); glShadeModel(GL_SMOOTH); glBlendFunc(GL_SRC_ALPHA, GL_ONE); glEnable(GL_BLEND); for (loop = 0; loop < NUM_OF_STARS; loop++) { star[loop].distance = (float)loop / NUM_OF_STARS * 5.0f; // Calculate distance from the centre // Give stars random rgb value star[loop].r = rand() % 256; star[loop].g = rand() % 256; star[loop].b = rand() % 256; } } void processEvents(sf::Window *app) { sf::Event event; while (app->GetEvent(event)) { if (event.Type == sf::Event::Closed) { app->Close(); } if (event.Type == sf::Event::KeyPressed && event.Key.Code == sf::Key::Escape) { app->Close(); } } } void renderGlScene(sf::Window *app) { app->SetActive(); // Clear color depth buffer glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Apply some transformations glMatrixMode(GL_MODELVIEW); glLoadIdentity(); // Select texture glBindTexture(GL_TEXTURE_2D, texture_handle[0]); for (loop = 0; loop < NUM_OF_STARS; loop++) { glLoadIdentity(); // Reset The View Before We Draw Each Star glTranslatef(0.0f, 0.0f, zoom); // Zoom Into The Screen (Using The Value In 'zoom') glRotatef(tilt, 1.0f, 0.0f, 0.0f); // Tilt The View (Using The Value In 'tilt') glRotatef(star[loop].angle, 0.0f, 1.0f, 0.0f); // Rotate To The Current Stars Angle glTranslatef(star[loop].distance, 0.0f, 0.0f); // Move Forward On The X Plane glRotatef(-star[loop].angle,0.0f,1.0f,0.0f); // Cancel The Current Stars Angle glRotatef(-tilt,1.0f,0.0f,0.0f); // Cancel The Screen Tilt if (twinkle) { glColor4ub(star[(NUM_OF_STARS - loop) - 1].r, star[(NUM_OF_STARS - loop)-1].g, star[(NUM_OF_STARS - loop) - 1].b, 255); glBegin(GL_QUADS); // Begin Drawing The Textured Quad glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 0.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f, 0.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f, 1.0f, 0.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, 1.0f, 0.0f); glEnd(); // Done Drawing The Textured Quad } glRotatef(spin,0.0f,0.0f,1.0f); // Rotate The Star On The Z Axis // Assign A Color Using Bytes glColor4ub(star[loop].r, star[loop].g, star[loop].b, 255); glBegin(GL_QUADS); // Begin Drawing The Textured Quad glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f,-1.0f, 0.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f,-1.0f, 0.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f, 1.0f, 0.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, 1.0f, 0.0f); glEnd(); // Done Drawing The Textured Quad spin += 0.01f; // Used To Spin The Stars star[loop].angle += (float)loop / NUM_OF_STARS; // Changes The Angle Of A Star star[loop].distance -= 0.01f; // Changes The Distance Of A Star if (star[loop].distance < 0.0f) { star[loop].distance += 5.0f; // Move The Star 5 Units From The Center star[loop].r = rand() % 256; // Give It A New Red Value star[loop].g = rand() % 256; // Give It A New Green Value star[loop].b = rand() % 256; // Give It A New Blue Value } } } I've looked over the code atleast 10 times now and I can't figure out the problem. Any help would be much appreciated.

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