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• getting bone base and tip positions from a transform matrix?

  - by ddos

  I need this for a Blender3d script, but you don't really need to know Blender to answer this. I need to get bone head and tip positions from a transform matrix read from a file. The position of base is the location part of the matrix, length of the bone (distance from base to tip) is the scale, position of the tip is calculated from the scale (distance from bone base) and rotation part of the matrix. So how to calculate these? bone.base([x,y,z]) # x,y,z - floats bone.tip([x,y,z])

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• GLSL: Strange light reflections

  - by Tom

  According to this tutorial I'm trying to make a normal mapping using GLSL, but something is wrong and I can't find the solution. The output render is in this image: Image1 in this image is a plane with two triangles and each of it is different illuminated (that is bad). The plane has 6 vertices. In the upper left side of this plane are 2 identical vertices (same in the lower right). Here are some vectors same for each vertice: normal vector = 0, 1, 0 (red lines on image) tangent vector = 0, 0,-1 (green lines on image) bitangent vector = -1, 0, 0 (blue lines on image) here I have one question: The two identical vertices does need to have the same tangent and bitangent? I have tried to make other values to the tangents but the effect was still similar. Here are my shaders Vertex shader: #version 130 // Input vertex data, different for all executions of this shader. in vec3 vertexPosition_modelspace; in vec2 vertexUV; in vec3 vertexNormal_modelspace; in vec3 vertexTangent_modelspace; in vec3 vertexBitangent_modelspace; // Output data ; will be interpolated for each fragment. out vec2 UV; out vec3 Position_worldspace; out vec3 EyeDirection_cameraspace; out vec3 LightDirection_cameraspace; out vec3 LightDirection_tangentspace; out vec3 EyeDirection_tangentspace; // Values that stay constant for the whole mesh. uniform mat4 MVP; uniform mat4 V; uniform mat4 M; uniform mat3 MV3x3; uniform vec3 LightPosition_worldspace; void main(){ // Output position of the vertex, in clip space : MVP * position gl_Position = MVP * vec4(vertexPosition_modelspace,1); // Position of the vertex, in worldspace : M * position Position_worldspace = (M * vec4(vertexPosition_modelspace,1)).xyz; // Vector that goes from the vertex to the camera, in camera space. // In camera space, the camera is at the origin (0,0,0). vec3 vertexPosition_cameraspace = ( V * M * vec4(vertexPosition_modelspace,1)).xyz; EyeDirection_cameraspace = vec3(0,0,0) - vertexPosition_cameraspace; // Vector that goes from the vertex to the light, in camera space. M is ommited because it's identity. vec3 LightPosition_cameraspace = ( V * vec4(LightPosition_worldspace,1)).xyz; LightDirection_cameraspace = LightPosition_cameraspace + EyeDirection_cameraspace; // UV of the vertex. No special space for this one. UV = vertexUV; // model to camera = ModelView vec3 vertexTangent_cameraspace = MV3x3 * vertexTangent_modelspace; vec3 vertexBitangent_cameraspace = MV3x3 * vertexBitangent_modelspace; vec3 vertexNormal_cameraspace = MV3x3 * vertexNormal_modelspace; mat3 TBN = transpose(mat3( vertexTangent_cameraspace, vertexBitangent_cameraspace, vertexNormal_cameraspace )); // You can use dot products instead of building this matrix and transposing it. See References for details. LightDirection_tangentspace = TBN * LightDirection_cameraspace; EyeDirection_tangentspace = TBN * EyeDirection_cameraspace; } Fragment shader: #version 130 // Interpolated values from the vertex shaders in vec2 UV; in vec3 Position_worldspace; in vec3 EyeDirection_cameraspace; in vec3 LightDirection_cameraspace; in vec3 LightDirection_tangentspace; in vec3 EyeDirection_tangentspace; // Ouput data out vec3 color; // Values that stay constant for the whole mesh. uniform sampler2D DiffuseTextureSampler; uniform sampler2D NormalTextureSampler; uniform sampler2D SpecularTextureSampler; uniform mat4 V; uniform mat4 M; uniform mat3 MV3x3; uniform vec3 LightPosition_worldspace; void main(){ // Light emission properties // You probably want to put them as uniforms vec3 LightColor = vec3(1,1,1); float LightPower = 40.0; // Material properties vec3 MaterialDiffuseColor = texture2D( DiffuseTextureSampler, vec2(UV.x,-UV.y) ).rgb; vec3 MaterialAmbientColor = vec3(0.1,0.1,0.1) * MaterialDiffuseColor; //vec3 MaterialSpecularColor = texture2D( SpecularTextureSampler, UV ).rgb * 0.3; vec3 MaterialSpecularColor = vec3(0.5,0.5,0.5); // Local normal, in tangent space. V tex coordinate is inverted because normal map is in TGA (not in DDS) for better quality vec3 TextureNormal_tangentspace = normalize(texture2D( NormalTextureSampler, vec2(UV.x,-UV.y) ).rgb*2.0 - 1.0); // Distance to the light float distance = length( LightPosition_worldspace - Position_worldspace ); // Normal of the computed fragment, in camera space vec3 n = TextureNormal_tangentspace; // Direction of the light (from the fragment to the light) vec3 l = normalize(LightDirection_tangentspace); // Cosine of the angle between the normal and the light direction, // clamped above 0 // - light is at the vertical of the triangle -> 1 // - light is perpendicular to the triangle -> 0 // - light is behind the triangle -> 0 float cosTheta = clamp( dot( n,l ), 0,1 ); // Eye vector (towards the camera) vec3 E = normalize(EyeDirection_tangentspace); // Direction in which the triangle reflects the light vec3 R = reflect(-l,n); // Cosine of the angle between the Eye vector and the Reflect vector, // clamped to 0 // - Looking into the reflection -> 1 // - Looking elsewhere -> < 1 float cosAlpha = clamp( dot( E,R ), 0,1 ); color = // Ambient : simulates indirect lighting MaterialAmbientColor + // Diffuse : "color" of the object MaterialDiffuseColor * LightColor * LightPower * cosTheta / (distance*distance) + // Specular : reflective highlight, like a mirror MaterialSpecularColor * LightColor * LightPower * pow(cosAlpha,5) / (distance*distance); //color.xyz = E; //color.xyz = LightDirection_tangentspace; //color.xyz = EyeDirection_tangentspace; } I have replaced the original color value by EyeDirection_tangentspace vector and then I got other strange effect but I can not link the image (not eunogh reputation) Is it possible that with this shaders is something wrong, or maybe in other place in my code e.g with my matrices? SOLVED Solved... 3 days needed for changing one letter from this: glBindBuffer(GL_ARRAY_BUFFER, vbo); glVertexAttribPointer ( 4, // attribute 3, // size GL_FLOAT, // type GL_FALSE, // normalized? sizeof(VboVertex), // stride (void*)(12*sizeof(float)) // array buffer offset ); to this: glBindBuffer(GL_ARRAY_BUFFER, vbo); glVertexAttribPointer ( 4, // attribute 3, // size GL_FLOAT, // type GL_FALSE, // normalized? sizeof(VboVertex), // stride (void*)(11*sizeof(float)) // array buffer offset ); see difference? :)

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• How can I plot a radius of all reachable points with pathfinding for a Mob?

  - by PugWrath

  I am designing a tactical turn based game. The maps are 2d, but do have varying level-layers and blocking objects/terrain. I'm looking for an algorithm for pathfinding which will allow me to show an opaque shape representing all of the possible max-distance pixels that a mob can move to, knowing the mob's max pixel distance. Any thoughts on this, or do I just need to write a good pathfinding algorithm and use it to find the cutoff points for any direction in which an obstacle exists?

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• Training of SEO - Open to All

  SEO is a very important subject matter nowadays and the SEO courses could be acquired through distance learning. Distance learning is basically a field of education which focuses upon giving education to students who are not physically present in a traditional classroom of a college or university.

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• Calculating a circle or sphere along a vector

  - by Sparky

  Updated this post and the one at Math SE (http://math.stackexchange.com/questions/127866/calculating-a-circle-or-sphere-along-a-vector), hope this makes more sense. I previously posted a question (about half an hour ago) involving computations along line segments, but the question and discussion were really off track and not what I was trying to get at. I am trying to work with an FPS engine I am attempting to build in Java. The problem I am encountering is with hitboxing. I am trying to calculate whether or not a "shot" is valid. I am working with several approaches and any insight would be helpful. I am not a native speaker of English nor skilled in Math so please bear with me. Player position is at P0 = (x0,y0,z0), Enemy is at P1 = (x1,y1,z1). I can of course compute the distance between them easily. The target needs a "hitbox" object, which is basically a square/rectangle/mesh either in front of, in, or behind them. Here are the solutions I am considering: I have ruled this out...doesn't seem practical. [Place a "hitbox" a small distance in front of the target. Then I would be able to find the distance between the player and the hitbox, and the hitbox and the target. It is my understanding that you can compute a circle with this information, and I could simply consider any shot within that circle a "hit". However this seems not to be an optimal solution, because it requires you to perform a lot of calculations and is not fully accurate.] Input, please! Place the hitbox "in" the player. This seems like the better solution. In this case what I need is a way to calculate a circle along the vector, at whatever position I wish (in this case, the distance between the two objects). Then I can pick some radius that encompasses the whole player, and count anything within this area a "hit". I am open to your suggestions. I'm trying to do this on paper and have no familiarity with game engines. If any software folk out there think I'm doing this the hard way, I'm open to help! Also - Anyone with JOGL/LWJGL experience, please chime in. Is this making sense?

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• Bluetooth push application

  - by Paul Kassey

  I am considering the technical viability of software that I want to write. Is there a way that I can push data to a phone (iPhone or Andriod) via Bluetooth without pairing with it? I want to be able to walk into a room and have a computer push data to my phone when I get a certain distance from it, or push data to any phone automatically when it comes within a certain distance to a Bluetooth-ready device?

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• How can I plot a radius of all reachable points with pathfinding for a Mob (XNA)?

  - by PugWrath

  I am designing a tactical turn based game. The maps are 2d, but do have varying level-layers and blocking objects/terrain. I'm looking for an algorithm for pathfinding which will allow me to show an opaque shape representing all of the possible max-distance pixels that a mob can move to, knowing the mob's max pixel distance. Any thoughts on this, or do I just need to write a good pathfinding algorithm and use it to find the cutoff points for any direction in which an obstacle exists?

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• 3D Graphics with XNA Game Studio 4.0 bug in light map?

  - by Eibis

  i'm following the tutorials on 3D Graphics with XNA Game Studio 4.0 and I came up with an horrible effect when I tried to implement the Light Map http://i.stack.imgur.com/BUWvU.jpg this effect shows up when I look towards the center of the house (and it moves with me). it has this shape because I'm using a sphere to represent light; using other light shapes gives different results. I'm using a class PreLightingRenderer: using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Graphics; using Dhpoware; using Microsoft.Xna.Framework.Content; namespace XNAFirstPersonCamera { public class PrelightingRenderer { // Normal, depth, and light map render targets RenderTarget2D depthTarg; RenderTarget2D normalTarg; RenderTarget2D lightTarg; // Depth/normal effect and light mapping effect Effect depthNormalEffect; Effect lightingEffect; // Point light (sphere) mesh Model lightMesh; // List of models, lights, and the camera public List<CModel> Models { get; set; } public List<PPPointLight> Lights { get; set; } public FirstPersonCamera Camera { get; set; } GraphicsDevice graphicsDevice; int viewWidth = 0, viewHeight = 0; public PrelightingRenderer(GraphicsDevice GraphicsDevice, ContentManager Content) { viewWidth = GraphicsDevice.Viewport.Width; viewHeight = GraphicsDevice.Viewport.Height; // Create the three render targets depthTarg = new RenderTarget2D(GraphicsDevice, viewWidth, viewHeight, false, SurfaceFormat.Single, DepthFormat.Depth24); normalTarg = new RenderTarget2D(GraphicsDevice, viewWidth, viewHeight, false, SurfaceFormat.Color, DepthFormat.Depth24); lightTarg = new RenderTarget2D(GraphicsDevice, viewWidth, viewHeight, false, SurfaceFormat.Color, DepthFormat.Depth24); // Load effects depthNormalEffect = Content.Load<Effect>(@"Effects\PPDepthNormal"); lightingEffect = Content.Load<Effect>(@"Effects\PPLight"); // Set effect parameters to light mapping effect lightingEffect.Parameters["viewportWidth"].SetValue(viewWidth); lightingEffect.Parameters["viewportHeight"].SetValue(viewHeight); // Load point light mesh and set light mapping effect to it lightMesh = Content.Load<Model>(@"Models\PPLightMesh"); lightMesh.Meshes[0].MeshParts[0].Effect = lightingEffect; this.graphicsDevice = GraphicsDevice; } public void Draw() { drawDepthNormalMap(); drawLightMap(); prepareMainPass(); } void drawDepthNormalMap() { // Set the render targets to 'slots' 1 and 2 graphicsDevice.SetRenderTargets(normalTarg, depthTarg); // Clear the render target to 1 (infinite depth) graphicsDevice.Clear(Color.White); // Draw each model with the PPDepthNormal effect foreach (CModel model in Models) { model.CacheEffects(); model.SetModelEffect(depthNormalEffect, false); model.Draw(Camera.ViewMatrix, Camera.ProjectionMatrix, Camera.Position); model.RestoreEffects(); } // Un-set the render targets graphicsDevice.SetRenderTargets(null); } void drawLightMap() { // Set the depth and normal map info to the effect lightingEffect.Parameters["DepthTexture"].SetValue(depthTarg); lightingEffect.Parameters["NormalTexture"].SetValue(normalTarg); // Calculate the view * projection matrix Matrix viewProjection = Camera.ViewMatrix * Camera.ProjectionMatrix; // Set the inverse of the view * projection matrix to the effect Matrix invViewProjection = Matrix.Invert(viewProjection); lightingEffect.Parameters["InvViewProjection"].SetValue(invViewProjection); // Set the render target to the graphics device graphicsDevice.SetRenderTarget(lightTarg); // Clear the render target to black (no light) graphicsDevice.Clear(Color.Black); // Set render states to additive (lights will add their influences) graphicsDevice.BlendState = BlendState.Additive; graphicsDevice.DepthStencilState = DepthStencilState.None; foreach (PPPointLight light in Lights) { // Set the light's parameters to the effect light.SetEffectParameters(lightingEffect); // Calculate the world * view * projection matrix and set it to // the effect Matrix wvp = (Matrix.CreateScale(light.Attenuation) * Matrix.CreateTranslation(light.Position)) * viewProjection; lightingEffect.Parameters["WorldViewProjection"].SetValue(wvp); // Determine the distance between the light and camera float dist = Vector3.Distance(Camera.Position, light.Position); // If the camera is inside the light-sphere, invert the cull mode // to draw the inside of the sphere instead of the outside if (dist < light.Attenuation) graphicsDevice.RasterizerState = RasterizerState.CullClockwise; // Draw the point-light-sphere lightMesh.Meshes[0].Draw(); // Revert the cull mode graphicsDevice.RasterizerState = RasterizerState.CullCounterClockwise; } // Revert the blending and depth render states graphicsDevice.BlendState = BlendState.Opaque; graphicsDevice.DepthStencilState = DepthStencilState.Default; // Un-set the render target graphicsDevice.SetRenderTarget(null); } void prepareMainPass() { foreach (CModel model in Models) foreach (ModelMesh mesh in model.Model.Meshes) foreach (ModelMeshPart part in mesh.MeshParts) { // Set the light map and viewport parameters to each model's effect if (part.Effect.Parameters["LightTexture"] != null) part.Effect.Parameters["LightTexture"].SetValue(lightTarg); if (part.Effect.Parameters["viewportWidth"] != null) part.Effect.Parameters["viewportWidth"].SetValue(viewWidth); if (part.Effect.Parameters["viewportHeight"] != null) part.Effect.Parameters["viewportHeight"].SetValue(viewHeight); } } } } that uses three effect: PPDepthNormal.fx float4x4 World; float4x4 View; float4x4 Projection; struct VertexShaderInput { float4 Position : POSITION0; float3 Normal : NORMAL0; }; struct VertexShaderOutput { float4 Position : POSITION0; float2 Depth : TEXCOORD0; float3 Normal : TEXCOORD1; }; VertexShaderOutput VertexShaderFunction(VertexShaderInput input) { VertexShaderOutput output; float4x4 viewProjection = mul(View, Projection); float4x4 worldViewProjection = mul(World, viewProjection); output.Position = mul(input.Position, worldViewProjection); output.Normal = mul(input.Normal, World); // Position's z and w components correspond to the distance // from camera and distance of the far plane respectively output.Depth.xy = output.Position.zw; return output; } // We render to two targets simultaneously, so we can't // simply return a float4 from the pixel shader struct PixelShaderOutput { float4 Normal : COLOR0; float4 Depth : COLOR1; }; PixelShaderOutput PixelShaderFunction(VertexShaderOutput input) { PixelShaderOutput output; // Depth is stored as distance from camera / far plane distance // to get value between 0 and 1 output.Depth = input.Depth.x / input.Depth.y; // Normal map simply stores X, Y and Z components of normal // shifted from (-1 to 1) range to (0 to 1) range output.Normal.xyz = (normalize(input.Normal).xyz / 2) + .5; // Other components must be initialized to compile output.Depth.a = 1; output.Normal.a = 1; return output; } technique Technique1 { pass Pass1 { VertexShader = compile vs_1_1 VertexShaderFunction(); PixelShader = compile ps_2_0 PixelShaderFunction(); } } PPLight.fx float4x4 WorldViewProjection; float4x4 InvViewProjection; texture2D DepthTexture; texture2D NormalTexture; sampler2D depthSampler = sampler_state { texture = ; minfilter = point; magfilter = point; mipfilter = point; }; sampler2D normalSampler = sampler_state { texture = ; minfilter = point; magfilter = point; mipfilter = point; }; float3 LightColor; float3 LightPosition; float LightAttenuation; // Include shared functions #include "PPShared.vsi" struct VertexShaderInput { float4 Position : POSITION0; }; struct VertexShaderOutput { float4 Position : POSITION0; float4 LightPosition : TEXCOORD0; }; VertexShaderOutput VertexShaderFunction(VertexShaderInput input) { VertexShaderOutput output; output.Position = mul(input.Position, WorldViewProjection); output.LightPosition = output.Position; return output; } float4 PixelShaderFunction(VertexShaderOutput input) : COLOR0 { // Find the pixel coordinates of the input position in the depth // and normal textures float2 texCoord = postProjToScreen(input.LightPosition) + halfPixel(); // Extract the depth for this pixel from the depth map float4 depth = tex2D(depthSampler, texCoord); // Recreate the position with the UV coordinates and depth value float4 position; position.x = texCoord.x * 2 - 1; position.y = (1 - texCoord.y) * 2 - 1; position.z = depth.r; position.w = 1.0f; // Transform position from screen space to world space position = mul(position, InvViewProjection); position.xyz /= position.w; // Extract the normal from the normal map and move from // 0 to 1 range to -1 to 1 range float4 normal = (tex2D(normalSampler, texCoord) - .5) * 2; // Perform the lighting calculations for a point light float3 lightDirection = normalize(LightPosition - position); float lighting = clamp(dot(normal, lightDirection), 0, 1); // Attenuate the light to simulate a point light float d = distance(LightPosition, position); float att = 1 - pow(d / LightAttenuation, 6); return float4(LightColor * lighting * att, 1); } technique Technique1 { pass Pass1 { VertexShader = compile vs_1_1 VertexShaderFunction(); PixelShader = compile ps_2_0 PixelShaderFunction(); } } PPShared.vsi has some common functions: float viewportWidth; float viewportHeight; // Calculate the 2D screen position of a 3D position float2 postProjToScreen(float4 position) { float2 screenPos = position.xy / position.w; return 0.5f * (float2(screenPos.x, -screenPos.y) + 1); } // Calculate the size of one half of a pixel, to convert // between texels and pixels float2 halfPixel() { return 0.5f / float2(viewportWidth, viewportHeight); } and finally from the Game class I set up in LoadContent with: effect = Content.Load(@"Effects\PPModel"); models[0] = new CModel(Content.Load(@"Models\teapot"), new Vector3(-50, 80, 0), new Vector3(0, 0, 0), 1f, Content.Load(@"Textures\prova_texture_autocad"), GraphicsDevice); house = new CModel(Content.Load(@"Models\house"), new Vector3(0, 0, 0), new Vector3((float)-Math.PI / 2, 0, 0), 35.0f, Content.Load(@"Textures\prova_texture_autocad"), GraphicsDevice); models[0].SetModelEffect(effect, true); house.SetModelEffect(effect, true); renderer = new PrelightingRenderer(GraphicsDevice, Content); renderer.Models = new List(); renderer.Models.Add(house); renderer.Models.Add(models[0]); renderer.Lights = new List() { new PPPointLight(new Vector3(0, 120, 0), Color.White * .85f, 2000) }; where PPModel.fx is: float4x4 World; float4x4 View; float4x4 Projection; texture2D BasicTexture; sampler2D basicTextureSampler = sampler_state { texture = ; addressU = wrap; addressV = wrap; minfilter = anisotropic; magfilter = anisotropic; mipfilter = linear; }; bool TextureEnabled = true; texture2D LightTexture; sampler2D lightSampler = sampler_state { texture = ; minfilter = point; magfilter = point; mipfilter = point; }; float3 AmbientColor = float3(0.15, 0.15, 0.15); float3 DiffuseColor; #include "PPShared.vsi" struct VertexShaderInput { float4 Position : POSITION0; float2 UV : TEXCOORD0; }; struct VertexShaderOutput { float4 Position : POSITION0; float2 UV : TEXCOORD0; float4 PositionCopy : TEXCOORD1; }; VertexShaderOutput VertexShaderFunction(VertexShaderInput input) { VertexShaderOutput output; float4x4 worldViewProjection = mul(World, mul(View, Projection)); output.Position = mul(input.Position, worldViewProjection); output.PositionCopy = output.Position; output.UV = input.UV; return output; } float4 PixelShaderFunction(VertexShaderOutput input) : COLOR0 { // Sample model's texture float3 basicTexture = tex2D(basicTextureSampler, input.UV); if (!TextureEnabled) basicTexture = float4(1, 1, 1, 1); // Extract lighting value from light map float2 texCoord = postProjToScreen(input.PositionCopy) + halfPixel(); float3 light = tex2D(lightSampler, texCoord); light += AmbientColor; return float4(basicTexture * DiffuseColor * light, 1); } technique Technique1 { pass Pass1 { VertexShader = compile vs_1_1 VertexShaderFunction(); PixelShader = compile ps_2_0 PixelShaderFunction(); } } I don't have any idea on what's wrong... googling the web I found that this tutorial may have some bug but I don't know if it's the LightModel fault (the sphere) or in a shader or in the class PrelightingRenderer. Any help is very appreciated, thank you for reading!

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• Optimizing transition/movement smoothness for a 2D flash game.

  - by Tom

  Update 6: Fenomenas suggested me to re-create everything as simple as possible. I had my doubts that this would make any difference as the algorithm remains the same, and performance did not seem to be the issue. Anyway, it was the only suggestion I got so here it is: 30 FPS: http://www.feedpostal.com/test/simple/30/SimpleMovement.html 40 FPS: http://www.feedpostal.com/test/simple/40/SimpleMovement.html 60 FPS: http://www.feedpostal.com/test/simple/60/SimpleMovement.html 100 FPS: http://www.feedpostal.com/test/simple/100/SimpleMovement.html The code: package { import flash.display.Sprite; import flash.events.Event; import flash.events.KeyboardEvent; import flash.utils.getTimer; [SWF(width="800", height="600", frameRate="40", backgroundColor="#000000")] public class SimpleMovement extends Sprite { private static const TURNING_SPEED:uint = 180; private static const MOVEMENT_SPEED:uint = 400; private static const RADIAN_DIVIDE:Number = Math.PI/180; private var playerObject:Sprite; private var shipContainer:Sprite; private var moving:Boolean = false; private var turningMode:uint = 0; private var movementTimestamp:Number = getTimer(); private var turningTimestamp:Number = movementTimestamp; public function SimpleMovement() { //step 1: create player object playerObject = new Sprite(); playerObject.graphics.lineStyle(1, 0x000000); playerObject.graphics.beginFill(0x6D7B8D); playerObject.graphics.drawRect(0, 0, 25, 50); //make it rotate around the center playerObject.x = 0 - playerObject.width / 2; playerObject.y = 0 - playerObject.height / 2; shipContainer = new Sprite(); shipContainer.addChild(playerObject); shipContainer.x = 100; shipContainer.y = 100; shipContainer.rotation = 180; addChild(shipContainer); //step 2: install keyboard hook when stage is ready addEventListener(Event.ADDED_TO_STAGE, stageReady, false, 0, true); //step 3: install rendering update poll addEventListener(Event.ENTER_FRAME, updatePoller, false, 0, true); } private function updatePoller(event:Event):void { var newTime:Number = getTimer(); //turning if (turningMode != 0) { var turningDeltaTime:Number = newTime - turningTimestamp; turningTimestamp = newTime; var rotation:Number = TURNING_SPEED * turningDeltaTime / 1000; if (turningMode == 1) shipContainer.rotation -= rotation; else shipContainer.rotation += rotation; } //movement if (moving) { var movementDeltaTime:Number = newTime - movementTimestamp; movementTimestamp = newTime; var distance:Number = MOVEMENT_SPEED * movementDeltaTime / 1000; var rAngle:Number = shipContainer.rotation * RADIAN_DIVIDE; //convert degrees to radian shipContainer.x += distance * Math.sin(rAngle); shipContainer.y -= distance * Math.cos(rAngle); } } private function stageReady(event:Event):void { //install keyboard hook stage.addEventListener(KeyboardEvent.KEY_DOWN, keyDown, false, 0, true); stage.addEventListener(KeyboardEvent.KEY_UP, keyUp, false, 0, true); } private final function keyDown(event:KeyboardEvent):void { if ((event.keyCode == 87) && (!moving)) //87 = W { movementTimestamp = getTimer(); moving = true; } if ((event.keyCode == 65) && (turningMode != 1)) //65 = A { turningTimestamp = getTimer(); turningMode = 1; } else if ((event.keyCode == 68) && (turningMode != 2)) //68 = D { turningTimestamp = getTimer(); turningMode = 2; } } private final function keyUp(event:KeyboardEvent):void { if ((event.keyCode == 87) && (moving)) moving = false; //87 = W if (((event.keyCode == 65) || (event.keyCode == 68)) && (turningMode != 0)) turningMode = 0; //65 = A, 68 = D } } } The results were as I expected. Absolutely no improvement. I really hope that someone has another suggestion as this thing needs fixing. Also, I doubt it's my system as I have a pretty good one (8GB RAM, Q9550 QuadCore intel, ATI Radeon 4870 512MB). Also, everyone else I asked so far had the same issue with my client. Update 5: another example of a smooth flash game just to demonstrate that my movement definitely is different! See http://www.spel.nl/game/bumpercraft.html Update 4: I traced the time before rendering (EVENT.RENDER) and right after rendering (EVENT.ENTER_FRAME), the results: rendering took: 14 ms rendering took: 14 ms rendering took: 12 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 14 ms rendering took: 12 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 14 ms rendering took: 12 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 14 ms rendering took: 14 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 24 ms rendering took: 18 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 232 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms The range is 12-16 ms. During these differences, the shocking/warping/flickering movement was already going on. There is also 1 peak of 232ms, at this time there was a relatively big warp. This is however not the biggest problme, the biggest problem are the continuous small warps during normal movement. Does this give anyone a clue? Update 3: After testing, I know that the following factors are not causing my problem: Bitmap's quality - changed with photoshop to an uglier 8 colours optimized graphic, no improvement at all. Constant rotation of image while turning - disabled it, no improvement at all Browser rendering - tried to use the flash player standalone, no improvement at all I am 100% convinced that the problem lies in either my code or in my algorithm. Please, help me out. It has been almost two weeks (1 week that I asked this question on SO) now and I still have to get my golden answer. Update 1: see bottom for full flex project source and a live demo demonstrating my problem. I'm working on a 2d flash game. Player ships are created as an object: ships[id] = new GameShip(); When movement and rotation information is available, this is being directed to the corresponding ship: ships[id].setMovementMode(1); //move forward Now, within this GameShip object movement works using the "Event.ENTER_FRAME" event: addEventListener(Event.ENTER_FRAME, movementHandler); The following function is then being run: private final function movementHandler(event:Event):void { var newTimeStamp:uint = UtilLib.getTimeStamp(); //set current timeStamp var distance:Number = (newTimeStamp - movementTimeStamp) / 1000 * movementSpeed; //speed = x pixels forward every 1 second movementTimeStamp = newTimeStamp; //update old timeStamp var diagonalChange:Array = getDiagonalChange(movementAngle, distance); //the diagonal position update based on angle and distance charX += diagonalChange[0]; charY += diagonalChange[1]; if (shipContainer) { //when the container is ready to be worked with shipContainer.x = charX; shipContainer.y = charY; } } private final function getDiagonalChange(angle:Number, distance:Number):Array { var rAngle:Number = angle * Math.PI/180; //convert degrees to radian return [Math.sin(rAngle) * distance, (Math.cos(rAngle) * distance) * -1]; } When the object is no longer moving, the event listener will be removed. The same method is being used for rotation. Everything works almost perfect. I've set the project's target FPS to 100 and created a FPS counter. According to the FPS counter, the average FPS in firefox is around 100, while the top is 1000 and the bottom is 22. I think that the bottom and top FPSs are only happening during the initialization of the client (startup). The problem is that the ship appears to be almost perfectly smooth, while it should be just that without the "almost" part. It's almost as if the ship is "flickering" very very fast, you can't actually see it but it's hard to focus on the object while it's moving with your eyes. Also, every now and then, there seems to be a bit of a framerate spike, as if the client is skipping a couple of frames, you then see it quickly warp. It is very difficult to explain what the real problem is, but in general it's that the movement is not perfectly smooth. So, do you have any suggestions on how to make the movement or transition of objects perfectly smooth? Update 1: I re-created the client to demonstrate my problem. Please check it out. The client: http://feedpostal.com/test/MovementTest.html The Actionscript Project (full source): http://feedpostal.com/test/MovementTest.rar An example of a smooth flash game (not created by me): http://www.gamesforwork.com/games/swf/Mission%20Racing_august_10th_2009.swf It took me a pretty long time to recreate this client side version, I hope this will help with solving the problem. Please note: yes, it is actually pretty smooth. But it is definitely not smooth enough.

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• actionscript3: reflect-class applied on rotationY

  - by algro

  Hi, I'm using a class which applies a visual reflection-effect to defined movieclips. I use a reflection-class from here: link to source. It works like a charm except when I apply a rotation to the movieclip. In my case the reflection is still visible but only a part of it. What am I doing wrong? How could I pass/include the rotation to the Reflection-Class ? Thanks in advance! This is how you apply the Reflection Class to your movieclip: var ref_mc:MovieClip = new MoviClip(); addChild(ref_mc); var r1:Reflect = new Reflect({mc:ref_mc, alpha:50, ratio:50,distance:0, updateTime:0,reflectionDropoff:1}); Now I apply a rotation to my movieclip: ref_mc.rotationY = 30; And Here the Reflect-Class: package com.pixelfumes.reflect{ import flash.display.MovieClip; import flash.display.DisplayObject; import flash.display.BitmapData; import flash.display.Bitmap; import flash.geom.Matrix; import flash.display.GradientType; import flash.display.SpreadMethod; import flash.utils.setInterval; import flash.utils.clearInterval; public class Reflect extends MovieClip{ //Created By Ben Pritchard of Pixelfumes 2007 //Thanks to Mim, Jasper, Jason Merrill and all the others who //have contributed to the improvement of this class //static var for the version of this class private static var VERSION:String = "4.0"; //reference to the movie clip we are reflecting private var mc:MovieClip; //the BitmapData object that will hold a visual copy of the mc private var mcBMP:BitmapData; //the BitmapData object that will hold the reflected image private var reflectionBMP:Bitmap; //the clip that will act as out gradient mask private var gradientMask_mc:MovieClip; //how often the reflection should update (if it is video or animated) private var updateInt:Number; //the size the reflection is allowed to reflect within private var bounds:Object; //the distance the reflection is vertically from the mc private var distance:Number = 0; function Reflect(args:Object){ /*the args object passes in the following variables /we set the values of our internal vars to math the args*/ //the clip being reflected mc = args.mc; //the alpha level of the reflection clip var alpha:Number = args.alpha/100; //the ratio opaque color used in the gradient mask var ratio:Number = args.ratio; //update time interval var updateTime:Number = args.updateTime; //the distance at which the reflection visually drops off at var reflectionDropoff:Number = args.reflectionDropoff; //the distance the reflection starts from the bottom of the mc var distance:Number = args.distance; //store width and height of the clip var mcHeight = mc.height; var mcWidth = mc.width; //store the bounds of the reflection bounds = new Object(); bounds.width = mcWidth; bounds.height = mcHeight; //create the BitmapData that will hold a snapshot of the movie clip mcBMP = new BitmapData(bounds.width, bounds.height, true, 0xFFFFFF); mcBMP.draw(mc); //create the BitmapData the will hold the reflection reflectionBMP = new Bitmap(mcBMP); //flip the reflection upside down reflectionBMP.scaleY = -1; //move the reflection to the bottom of the movie clip reflectionBMP.y = (bounds.height*2) + distance; //add the reflection to the movie clip's Display Stack var reflectionBMPRef:DisplayObject = mc.addChild(reflectionBMP); reflectionBMPRef.name = "reflectionBMP"; //add a blank movie clip to hold our gradient mask var gradientMaskRef:DisplayObject = mc.addChild(new MovieClip()); gradientMaskRef.name = "gradientMask_mc"; //get a reference to the movie clip - cast the DisplayObject that is returned as a MovieClip gradientMask_mc = mc.getChildByName("gradientMask_mc") as MovieClip; //set the values for the gradient fill var fillType:String = GradientType.LINEAR; var colors:Array = [0xFFFFFF, 0xFFFFFF]; var alphas:Array = [alpha, 0]; var ratios:Array = [0, ratio]; var spreadMethod:String = SpreadMethod.PAD; //create the Matrix and create the gradient box var matr:Matrix = new Matrix(); //set the height of the Matrix used for the gradient mask var matrixHeight:Number; if (reflectionDropoff<=0) { matrixHeight = bounds.height; } else { matrixHeight = bounds.height/reflectionDropoff; } matr.createGradientBox(bounds.width, matrixHeight, (90/180)*Math.PI, 0, 0); //create the gradient fill gradientMask_mc.graphics.beginGradientFill(fillType, colors, alphas, ratios, matr, spreadMethod); gradientMask_mc.graphics.drawRect(0,0,bounds.width,bounds.height); //position the mask over the reflection clip gradientMask_mc.y = mc.getChildByName("reflectionBMP").y - mc.getChildByName("reflectionBMP").height; //cache clip as a bitmap so that the gradient mask will function gradientMask_mc.cacheAsBitmap = true; mc.getChildByName("reflectionBMP").cacheAsBitmap = true; //set the mask for the reflection as the gradient mask mc.getChildByName("reflectionBMP").mask = gradientMask_mc; //if we are updating the reflection for a video or animation do so here if(updateTime > -1){ updateInt = setInterval(update, updateTime, mc); } } public function setBounds(w:Number,h:Number):void{ //allows the user to set the area that the reflection is allowed //this is useful for clips that move within themselves bounds.width = w; bounds.height = h; gradientMask_mc.width = bounds.width; redrawBMP(mc); } public function redrawBMP(mc:MovieClip):void { // redraws the bitmap reflection - Mim Gamiet [2006] mcBMP.dispose(); mcBMP = new BitmapData(bounds.width, bounds.height, true, 0xFFFFFF); mcBMP.draw(mc); } private function update(mc):void { //updates the reflection to visually match the movie clip mcBMP = new BitmapData(bounds.width, bounds.height, true, 0xFFFFFF); mcBMP.draw(mc); reflectionBMP.bitmapData = mcBMP; } public function destroy():void{ //provides a method to remove the reflection mc.removeChild(mc.getChildByName("reflectionBMP")); reflectionBMP = null; mcBMP.dispose(); clearInterval(updateInt); mc.removeChild(mc.getChildByName("gradientMask_mc")); } } }

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• How to Zip one IEnumerable with itself

  - by wageoghe

  I am implementing some math algorithms based on lists of points, like Distance, Area, Centroid, etc. Just like in this post: http://stackoverflow.com/questions/2227828/find-the-distance-required-to-navigate-a-list-of-points-using-linq That post describes how to calculate the total distance of a sequence of points (taken in order) by essentially zipping the sequence "with itself", generating the sequence for Zip by offsetting the start position of the original IEnumerable by 1. So, given the Zip extension in .Net 4.0, assuming Point for the point type, and a reasonable Distance formula, you can make calls like this to generate a sequence of distances from one point to the next and then to sum the distances: var distances = points.Zip(points.Skip(1),Distance); double totalDistance = distances.Sum(); Area and Centroid calculations are similar in that they need to iterate over the sequence, processing each pair of points (points[i] and points[i+1]). I thought of making a generic IEnumerable extension suitable for implementing these (and possibly other) algorithms that operate over sequences, taking two items at a time (points[0] and points[1], points[1] and points[2], ..., points[n-1] and points[n] (or is it n-2 and n-1 ...) and applying a function. My generic iterator would have a similar signature to Zip, but it would not receive a second sequence to zip with as it is really just going to zip with itself. My first try looks like this: public static IEnumerable<TResult> ZipMyself<TSequence, TResult>(this IEnumerable<TSequence> seq, Func<TSequence, TSequence, TResult> resultSelector) { return seq.Zip(seq.Skip(1),resultSelector); } With my generic iterator in place, I can write functions like this: public static double Length(this IEnumerable<Point> points) { return points.ZipMyself(Distance).Sum(); } and call it like this: double d = points.Length(); and double GreensTheorem(Point p1, Point p1) { return p1.X * p2.Y - p1.Y * p2.X; } public static double SignedArea(this IEnumerable<Point> points) { return points.ZipMyself(GreensTheorem).Sum() / 2.0 } public static double Area(this IEnumerable<Point> points) { return Math.Abs(points.SignedArea()); } public static bool IsClockwise(this IEnumerable<Point> points) { return SignedArea(points) < 0; } and call them like this: double a = points.Area(); bool isClockwise = points.IsClockwise(); In this case, is there any reason NOT to implement "ZipMyself" in terms of Zip and Skip(1)? Is there already something in LINQ that automates this (zipping a list with itself) - not that it needs to be made that much easier ;-) Also, is there better name for the extension that might reflect that it is a well-known pattern (if, indeed it is a well-known pattern)? Had a link here for a StackOverflow question about area calculation. It is question 2432428. Also had a link to Wikipedia article on Centroid. Just go to Wikipedia and search for Centroid if interested. Just starting out, so don't have enough rep to post more than one link,

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• How should I generate and store the boundries of a cave?

  - by Bob Roberts

  I am making a small cave copter game (seriously, where did this type of game come from anyway) and I am trying to figure out how to make and store the procedural generated walls. I am thinking about creating the walls by randomly picking two points away from the center of the screen. They will be no closer than the height of helicopter and no further than the edge of the screen, weighted to prefer to go in the same direction as the point prior so I end up with stalactites and stalagmites and not just noise, at set intervals of distance. To store, perhaps parallel arrays/lists, one for distance from center to top screen and one for distance from center to bottom. Am I way off base with my thinking? I just want the cave to be varied and challenging, I just have never worked with generating data like this. Edit: Woah, I just realized that my idea would lead to a player being able to stay in the middle of the screen and win. That isn't right at all. So the very basis of how I was going to generate is wrong. Edit 2: I also realized I left out a very crucial point. Part of the mechanics of the game will let the player go backwards therefor the data structure should be continuous.

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• OpenGL ES rotate texture

  - by 0xSina

  I just got started with OpenGL ES... I have a fragment: const char * sFragment = _STRINGIFY( varying highp vec2 coordinate; precision mediump float; uniform vec4 maskC; uniform float threshold; uniform sampler2D videoframe; uniform sampler2D videosprite; uniform vec4 mask; uniform vec4 maskB; uniform int recording; vec3 normalize(vec3 color, float meanr) { return color*vec3(0.75 + meanr, 1., 1. - meanr); } void main() { float d; float dB; float dC; float meanr; float meanrB; float meanrC; float minD; vec4 pixelColor; vec4 spriteColor; pixelColor = texture2D(videoframe, coordinate); spriteColor = texture2D(videosprite, coordinate); meanr = (pixelColor.r + mask.r)/8.; meanrB = (pixelColor.r + maskB.r)/8.; meanrC = (pixelColor.r + maskC.r)/8.; d = distance(normalize(pixelColor.rgb, meanr), normalize(mask.rgb, meanr)); dB = distance(normalize(pixelColor.rgb, meanrB), normalize(maskB.rgb, meanrB)); dC = distance(normalize(pixelColor.rgb, meanrC), normalize(maskC.rgb, meanrC)); minD = min(d, dB); minD = min(minD, dC); gl_FragColor = spriteColor; if (minD > threshold) { gl_FragColor = pixelColor; } } Now, depending on wether recording is 0 or 1, I want to rotate uniform sampler2D videosprite 180 degrees (reflection in x-axis, flip vertically). How can I do that? I found the function glRotatef(), but how do i specify that I want to rotate video sprite and not videoframe? Thanks

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• Converting a bounded knapsack problem to 0/1 knapsack problem

  - by Ants

  I ran across a problem where goal was to use dynamic programming (instead of other approaches). There is a distance to be spanned, and a set of cables of different lengths. What is the minimum number of cables needed to span the distance exactly? To me this looked like a knapsack problem, but since there could be multiples of a particular length, it was a bounded knapsack problem, rather than a 0/1 knapsack problem. (Treat the value of each item to be its weight.) Taking the naive approach (and not caring about the expansion of the search space), the method I used to convert the bounded knapsack problem into a 0/1 knapsack problem, was simply break up the multiples into singles and apply the well-known dynamic programming algorithm. Unfortunately, this leads to sub-optimal results. For example, given cables: 1 x 10ft, 1 x 7ft, 1 x 6ft, 5 x 3ft, 6 x 2ft, 7 x 1ft If the target span is 13ft, the DP algorithm picks 7+6 to span the distance. A greedy algorithm would have picked 10+3, but it's a tie for minimum number of cables. The problem arises, when trying to span 15ft. The DP algorithm ended up picking 6+3+3+3 to get 4 cables, while the greedy algorithm correctly picks 10+3+2 for only 3 cables. Anyway, doing some light scanning of converting bounded to 0/1, it seems like the well-known approach to convert multiple items to { p, 2p, 4p ... }. My question is how does this conversion work if p+2p+4p does not add up to the number of multiple items. For example: I have 5 3ft cables. I can't very well add { 3, 2x3, 4x3 } because 3+2x3+4x3 5x3. Should I add { 3, 4x3 } instead? [I'm currently trying to grok the "Oregon Trail Knapsack Problem" paper, but it currently looks like the approach used there is not dynamic programming.]

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• Pathfinding with MicroPather : costs calculations with sectors and portals

  - by Adan

  Hello, I'm considering using micropather to help me with pathfinding. I'm not using a discrete map : I'm working in 2d with sectors and portales. However, I'm just wondering what is the best way to compute costs with this library in this context. Just to be more clear about geometrical shapes I'm using : sectors are basically convex polygons, and portals are segments that lies on sector's edge. Micropather exposes a pure virtual Graph class that you must inherate and overrides 3 functions. I understand how pathfinding works, so there's no problem in overriding those functions. Right now, my implementation give me results, i.e I'm able to find a path in my map, but I'm not sure I'm using an optimal solution. For the AdjacentCost method : I just take the distance between sector's centers as the cost. I think a better solution should be to use the portal between the two sectors, compute its center, and then the cost should be : distance( sector A center, portal center ) + distance ( sector B center, portal center ). I'm pretty sure the approximation I'm using with just sector's center is enough for most cases, but maybe with thin and long sectors that are perpendicular, this approximation could mislead the A* algorithm. For the LeastCostEstimate method : I just take the midpoint of the two sectors. So, as you understand, I'm always working with sectors' centers, and it's working fine. And I'm pretty sure there's a better way to work. Any suggestions or feedbacks? Thanks in advance!

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• Points around a circumference C#

  - by Lautaro

  Im trying to get a list of vectors that go around a circle, but i keep getting the circle to go around several times. I want one circel and the dots to be placed along its circumference. I want the first dot to start at 0 and the last dot to end just before 360. Also i need to be able to calculate the spacing by the ammount of points. List<Vector2> pointsInPath = new List<Vector2>(); private int ammountOfPoints = 5; private int blobbSize = 200; private Vector2 topLeft = new Vector2(100, 100); private Vector2 blobbCenter; private int endAngle = 50; private int angleIncrementation; public Blobb() { blobbCenter = new Vector2(blobbSize / 2, blobbSize / 2) + topLeft; angleIncrementation = endAngle / ammountOfPoints; for (int i = 0; i < ammountOfPoints; i++) { pointsInPath.Add(getPointByAngle(i * angleIncrementation, 100, blobbCenter)); // pointsInPath.Add(getPointByAngle(i * angleIncrementation, blobbSize / 2, blobbCenter)); } } private Vector2 getPointByAngle(float angle, float distance, Vector2 centre) { return new Vector2((float)(distance * Math.Cos(angle) ), (float)(distance * Math.Sin(angle))) + centre ; }

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• What do ptLineDist and relativeCCW do?

  - by Fasih Khatib

  I saw these methods in the Line2D Java Docs but did not understand what they do? Javadoc for ptLineDist says: Returns the distance from a point to this line. The distance measured is the distance between the specified point and the closest point on the infinitely-extended line defined by this Line2D. If the specified point intersects the line, this method returns 0.0 Doc for relativeCCW says: Returns an indicator of where the specified point (PX, PY) lies with respect to the line segment from (X1, Y1) to (X2, Y2). The return value can be either 1, -1, or 0 and indicates in which direction the specified line must pivot around its first endpoint, (X1, Y1), in order to point at the specified point (PX, PY). A return value of 1 indicates that the line segment must turn in the direction that takes the positive X axis towards the negative Y axis. In the default coordinate system used by Java 2D, this direction is counterclockwise. A return value of -1 indicates that the line segment must turn in the direction that takes the positive X axis towards the positive Y axis. In the default coordinate system, this direction is clockwise. A return value of 0 indicates that the point lies exactly on the line segment. Note that an indicator value of 0 is rare and not useful for determining colinearity because of floating point rounding issues. If the point is colinear with the line segment, but not between the endpoints, then the value will be -1 if the point lies "beyond (X1, Y1)" or 1 if the point lies "beyond (X2, Y2)".

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• Predictive firing (in a tile-based game)

  - by n00bster

  I have a (turn-based) tile-based game, in which you can shoot at entities. You can move around with mouse and keyboard, it's all tile-based, except that bullets move "freely". I've got it all working just fine except that when I move, and the creatures shoot towards the player, they shoot towards the previous tiles.. resulting in ugly looking "miss hits" or lag. I think I need to implement some kind of predictive firing based on the bullet speed and the distance, but I don't quite know how to implement such a thing... Here's a simplified snip of my firing code. class Weapon { public void fire(int x, int y) { ... ... ... Creature owner = getOwner(); Tile targetTile = Zone.getTileAt(x, y); float dist = Vector.distance(owner.getCenterPosition(), targetTile.getCenterPosition()); Bullet b = new Bullet(); b.setPosition(owner.getCenterPosition()); // Take dist into account in the duration to get constant speed regardless of distance float duration = dist / 600f; // Moves the bullet to the centre of the target tile in the given amount of time (in seconds) b.moveTo(targetTile.getCenterPosition(), duration); // This is what I'm after // Vector v = predict the position // b.moveTo(v, duration); Zone.add(bullet); // Now the bullet gets "ticked" and moveTo will be implemented } } Movement of creatures is as simple as setting the position variable. If you need more information, just ask.

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• How do I make cars on a one-dimensional track avoid collisions?

  - by user990827

  Using three.js, I use a simple spline to represent a road. Cars can only move forward on the spline. A car should be able to slow-down behind a slow moving car. I know how to calculate the distance between 2 cars, but how to calculate the proper speed in each game update? At the moment I simply do something like this: this.speed += (this.maxSpeed - this.speed) * 0.02; // linear interpolation to maxSpeed // the position on the spline (0.0 - 1.0) this.position += this.speed / this.road.spline.getLength(); This works. But how to implement the slow-down part? // transform from floats (0.0 - 1.0) into actual units var carInFrontPosition = carInFront.position * this.road.spline.getLength(); var myPosition = this.position * this.road.spline.getLength(); var distance = carInFrontPosition - myPosition; // WHAT TO DO HERE WITH THE DISTANCE? // HOW TO CALCULATE MY NEW SPEED? Obviously I have to somehow take current speed of the cars into account for calculation. Besides different maxSpeeds, I want each car to also have a different mass (causing it to accelerate slower/faster). But this mass has to be then also taken into account for braking (slowing down) so they don't crash into each other.

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• Any faster method?

  - by rajeshverma423

  Manhattan distance is used to the center in chess code that uses an 0x88 board . 0x88 board is 128 square. public static final byte DISTANCE[] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 6, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 6, 5, 6, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 6, 5, 4, 5, 6, 7, 0, 0, 0, 0, 0, 0, 0, 0, 7, 6, 5, 4, 3, 4, 5, 6, 7, 0, 0, 0, 0, 0, 0, 7, 6, 5, 4, 3, 2, 3, 4, 5, 6, 7, 0, 0, 0, 0, 7, 6, 5, 4, 3, 2, 1, 2, 3, 4, 5, 6, 7, 0, 0, 7, 6, 5, 4, 3, 2, 1, 0, 1, 2, 3, 4, 5, 6, 7, 0, 0, 7, 6, 5, 4, 3, 2, 1, 2, 3, 4, 5, 6, 7, 0, 0, 0, 0, 7, 6, 5, 4, 3, 2, 3, 4, 5, 6, 7, 0, 0, 0, 0, 0, 0, 7, 6, 5, 4, 3, 4, 5, 6, 7, 0, 0, 0, 0, 0, 0, 0, 0, 7, 6, 5, 4, 5, 6, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 6, 5, 6, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 6, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }; Is there any other faster method instead of 0x88 to find distance?

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• How to best design a date/geographic proximity query on GAE?

  - by Dane

  Hi all, I'm building a directory for finding athletic tournaments on GAE with web2py and a Flex front end. The user selects a location, a radius, and a maximum date from a set of choices. I have a basic version of this query implemented, but it's inefficient and slow. One way I know I can improve it is by condensing the many individual queries I'm using to assemble the objects into bulk queries. I just learned that was possible. But I'm also thinking about a more extensive redesign that utilizes memcache. The main problem is that I can't query the datastore by location because GAE won't allow multiple numerical comparison statements (<,<=,=,) in one query. I'm already using one for date, and I'd need TWO to check both latitude and longitude, so it's a no go. Currently, my algorithm looks like this: 1.) Query by date and select 2.) Use destination function from geopy's distance module to find the max and min latitude and longitudes for supplied distance 3.) Loop through results and remove all with lat/lng outside max/min 4.) Loop through again and use distance function to check exact distance, because step 2 will include some areas outside the radius. Remove results outside supplied distance (is this 2/3/4 combination inefficent?) 5.) Assemble many-to-many lists and attach to objects (this is where I need to switch to bulk operations) 6.) Return to client Here's my plan for using memcache.. let me know if I'm way out in left field on this as I have no prior experience with memcache or server caching in general. -Keep a list in the cache filled with "geo objects" that represent all my data. These have five properties: latitude, longitude, event_id, event_type (in anticipation of expanding beyond tournaments), and start_date. This list will be sorted by date. -Also keep a dict of pointers in the cache which represent the start and end indices in the cache for all the date ranges my app uses (next week, 2 weeks, month, 3 months, 6 months, year, 2 years). -Have a scheduled task that updates the pointers daily at 12am. -Add new inserts to the cache as well as the datastore; update pointers. Using this design, the algorithm would now look like: 1.) Use pointers to slice off appropriate chunk of list based on supplied date. 2-4.) Same as above algorithm, except with geo objects 5.) Use bulk operation to select full tournaments using remaining geo objects' event_ids 6.) Assemble many-to-manys 7.) Return to client Thoughts on this approach? Many thanks for reading and any advice you can give. -Dane

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• point light illumination using Phong model

  - by Myx

  Hello: I wish to render a scene that contains one box and a point light source using the Phong illumination scheme. The following are the relevant code snippets for my calculation: R3Rgb Phong(R3Scene *scene, R3Ray *ray, R3Intersection *intersection) { R3Rgb radiance; if(intersection->hit == 0) { radiance = scene->background; return radiance; } ... // obtain ambient term ... // this is zero for my test // obtain emissive term ... // this is also zero for my test // for each light in the scene, obtain calculate the diffuse and specular terms R3Rgb intensity_diffuse(0,0,0,1); R3Rgb intensity_specular(0,0,0,1); for(unsigned int i = 0; i < scene->lights.size(); i++) { R3Light *light = scene->Light(i); R3Rgb light_color = LightIntensity(scene->Light(i), intersection->position); R3Vector light_vector = -LightDirection(scene->Light(i), intersection->position); // check if the light is "behind" the surface normal if(normal.Dot(light_vector)<=0) continue; // calculate diffuse reflection if(!Kd.IsBlack()) intensity_diffuse += Kd*normal.Dot(light_vector)*light_color; if(Ks.IsBlack()) continue; // calculate specular reflection ... // this I believe to be irrelevant for the particular test I'm doing } radiance = intensity_diffuse; return radiance; } R3Rgb LightIntensity(R3Light *light, R3Point position) { R3Rgb light_intensity; double distance; double denominator; if(light->type != R3_DIRECTIONAL_LIGHT) { distance = (position-light->position).Length(); denominator = light->constant_attenuation + (light->linear_attenuation*distance) + (light->quadratic_attenuation*distance*distance); } switch(light->type) { ... case R3_POINT_LIGHT: light_intensity = light->color/denominator; break; ... } return light_intensity; } R3Vector LightDirection(R3Light *light, R3Point position) { R3Vector light_direction; switch(light->type) { ... case R3_POINT_LIGHT: light_direction = position - light->position; break; ... } light_direction.Normalize(); return light_direction; } I believe that the error must be somewhere in either LightDirection(...) or LightIntensity(...) functions because when I run my code using a directional light source, I obtain the desired rendered image (thus this leads me to believe that the Phong illumination equation is correct). Also, in Phong(...), when I computed the intensity_diffuse and while debugging, I divided light_color by 10, I was obtaining a resulting image that looked more like what I need. Am I calculating the light_color correctly? Thanks.

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• Triangle Line-Segment Intersection - detecting near misses

  - by Will

  A ray is a very poor approximation of a player! I think approximating a player with a sphere traveling a straight line each game tick will solve my problems of the player intersecting edges of scenery because their line segment missed it yet their own model is not infinitely thin... I have a 3D triangle and a line segment. I have the normal triangle-line-segment intersection code which I admit I have only a woolly grasp of. To model movement and compute collisions of the player I have to determine if a line passes within sphere-radius of a triangle. But I can find no convenient line near-miss intersection code! Here's the classic triangle intersection ### commented ### code with my starting assumptions: function triangle_ray_intersection(a,b,c,ray_origin,ray_dir,ray_radius) { // http://softsurfer.com/Archive/algorithm_0105/algorithm_0105.htm#intersect_RayTriangle%28%29 // get triangle edge vectors and plane normal var u = vec3_sub(b,a); var v = vec3_sub(c,a); var n = vec3_cross(u,v); if(n[0]==0 && n[1]==0 && n[2]==0) return null; // triangle is degenerate var w0 = vec3_sub(ray_origin,a); var j = vec3_dot(n,ray_dir); if(Math.abs(j) < 0.00000001) { //### if parallel, might still pass within ray_radius of it return null; // parallel, disjoint or on plane } var i = -vec3_dot(n,w0); // get intersect point of ray with triangle plane var k = i / j; if(k < 0.0) return null; // ray goes away from triangle //### as its a line segment, k > 1+ray_radius means no intersect var hit = vec3_add(ray_origin,vec3_scale(ray_dir,k)); // intersect point of ray and plane // is I inside T? //### here I'm a bit lost; this is presumably computing barycentric coordinates? var uu = vec3_dot(u,u); var uv = vec3_dot(u,v); var vv = vec3_dot(v,v); var w = vec3_sub(hit,a); var wu = vec3_dot(w,u); var wv = vec3_dot(w,v); var D = uv * uv - uu * vv; var s = (uv * wv - vv * wu) / D; //### therefore, compute if its within ray_radius scaled to the 0..1 of barycentric coordinates? if(s<0.0 || s>1.0) return null; // I is outside T var t = (uv * wu - uu * wv) / D; if(t<0.0 || (s+t)>1.0) return null; // I is outside T //### finally, if it passses a barycentric test it might still be too far //### to a point; must check that its distance from a corner is within ray_radius too if more than one barycentric coord is >1 //### so we have rounded corners... return [hit,n]; // I is in T } Given the distance between the point of plane intersection and each corner, I ought to be able to determine distance at world scale of how far beyond the edge - beyond 1.0 in barycentric coordinates for each axis - that point is... At this point my head explodes! Is this the right track? What's the actual code? UPDATE: you can earn 100 pts on SO if you answer this question there...! How can you determine if a line segment passes within some distance of a triangle?

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• XNA - 3D AABB collision detection and response

  - by fastinvsqrt

  I've been fiddling around with 3D AABB collision in my voxel engine for the last couple of days, and every method I've come up with thus far has been almost correct, but each one never quite worked exactly the way I hoped it would. Currently what I do is get two bounding boxes for my entity, one modified by the X translation component and the other by the Z component, and check if each collides with any of the surrounding chunks (chunks have their own octrees that are populated only with blocks that support collision). If there is a collision, then I cast out rays into that chunk to get the shortest collision distance, and set the translation component to that distance if the component is greater than the distance. The problem is that sometimes collisions aren't even registered. Here's a video on YouTube that I created showing what I mean. I suspect the problem may be with the rays that I cast to get the collision distance not being where I think they are, but I'm not entirely sure what would be wrong with them if they are indeed the problem. Here is my code for collision detection and response in the X direction (the Z direction is basically the same): // create the XZ offset vector Vector3 offsXZ = new Vector3( ( _translation.X > 0.0f ) ? SizeX / 2.0f : ( _translation.X < 0.0f ) ? -SizeX / 2.0f : 0.0f, 0.0f, ( _translation.Z > 0.0f ) ? SizeZ / 2.0f : ( _translation.Z < 0.0f ) ? -SizeZ / 2.0f : 0.0f ); // X physics BoundingBox boxx = GetBounds( _translation.X, 0.0f, 0.0f ); if ( _translation.X > 0.0f ) { foreach ( Chunk chunk in surrounding ) { if ( chunk.Collides( boxx ) ) { float dist = GetShortestCollisionDistance( chunk, Vector3.Right, offsXZ ) - 0.0001f; if ( dist < _translation.X ) { _translation.X = dist; } } } } else if ( _translation.X < 0.0f ) { foreach ( Chunk chunk in surrounding ) { if ( chunk.Collides( boxx ) ) { float dist = GetShortestCollisionDistance( chunk, Vector3.Left, offsXZ ) - 0.0001f; if ( dist < -_translation.X ) { _translation.X = -dist; } } } } And here is my implementation for GetShortestCollisionDistance: private float GetShortestCollisionDistance( Chunk chunk, Vector3 rayDir, Vector3 offs ) { int startY = (int)( -SizeY / 2.0f ); int endY = (int)( SizeY / 2.0f ); int incY = (int)Cube.Size; float dist = Chunk.Size; for ( int y = startY; y <= endY; y += incY ) { // Position is the center of the entity's bounding box Ray ray = new Ray( new Vector3( Position.X + offs.X, Position.Y + offs.Y + y, Position.Z + offs.Z ), rayDir ); // Chunk.GetIntersections(Ray) returns Dictionary<Block, float?> foreach ( var pair in chunk.GetIntersections( ray ) ) { if ( pair.Value.HasValue && pair.Value.Value < dist ) { dist = pair.Value.Value; } } } return dist; } I realize some of this code can be consolidated to help with speed, but my main concern right now is to get this bit of physics programming to actually work.

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• OpenStreetMap Proximity search using mySQL

  - by Chris

  Hi, I'm just playing around with a dataset of my region generated by JOSM. I moved it into a mySQL DB with the 0.6 API scheme using Osmosis and now I'm desperately trying the following: I want to get all streets of a city. AFAIK there is no tag/relation in the OSM data to determine this so I tried it using a proximity search to get all nodes in a radius around a node representing the city center. Most of the time I looked at the approaches here: http://stackoverflow.com/questions/574691/mysql-great-circle-distance-haversine-formula What I got is the following SQL code that should get me the closest 100 nodes around the node with id 36187002 and within a radius of 10km. set @nodeid = 36187002; set @dist = 10; select longitude, latitude into @mylon, @mylat from nodes where id=@nodeid limit 1; SELECT id, ( 6371 * acos( cos( radians(@mylon) ) * cos( radians( latitude ) ) * cos( radians( longitude ) - radians(@mylat) ) + sin( radians(@mylon) ) * sin( radians( latitude ) ) ) ) AS distance FROM nodes HAVING distance < @dist ORDER BY distance LIMIT 0 , 100; Well.. it doesn't work. :( I guess the main problem is that OSM lats/lons are multiplied by 10.000.000 and I don't know how I can correct this function to make it work. Any ideas about this? All solutions/alternatives are very welcome! Have a nice weekend! Chris

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