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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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• Cocos2d copied actions not responding?

  - by Stephen

  I am running an animation on 2 sprites like so: -(void) startFootballAnimation { CCAnimation* footballAnim = [CCAnimation animationWithFrame:@"Football" frameCount:60 delay:0.005f]; spiral = [CCAnimate actionWithAnimation:footballAnim]; CCRepeatForever* repeat = [CCRepeatForever actionWithAction:spiral]; [self runAction:repeat]; [secondFootball runAction:[[repeat copy] autorelease]]; } The problem I am having is I call this method: - (void) slowAnimation { [spiral setDuration:[spiral duration] + 0.01]; } and it only slows down the first sprites animation and not the second one. Do I need to do something different with copied actions to get them to react to the slowing of the animation?

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• Preferred way to render text in OpenGL

  - by dukeofgaming

  Hi, I'm about tu pick up computer graphics once again for an university project. For a previous project I used a library called ftgl that didn't leave me quite satisfied as it felt kind of heavy (I tried all rendering techniques, text rendering didn't scale very well). My question is, is there a good and efficient library for this?, if not, what would be the way to implement fast but nice looking text?. Some intended uses are: Floating object/character labels Dialogues Menus HUD Regards and thanks in advance. EDIT: Preferrably that it can load fonts

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• "has no motion" warnings

  - by Adam R. Grey

  When I reimport my project's Library, I get lots of warnings such as State combat.Ghoul Attack has no motion but I have no idea why. In this specific case, I looked up Ghoul Attack. Here's the state in which it appears, in the only animator controller that includes anything called Ghoul Attack: State: m_ObjectHideFlags: 3 m_PrefabParentObject: {fileID: 0} m_PrefabInternal: {fileID: 0} m_Name: Ghoul Attack m_Speed: 1 m_CycleOffset: 0 m_Motions: - {fileID: 7400000, guid: 0db269712a91fd641b6dd5e0e4c6d507, type: 3} - {fileID: 0} m_ParentStateMachine: {fileID: 110708233} m_Position: {x: 492, y: 132, z: 0} m_IKOnFeet: 1 m_Mirror: 0 m_Tag: I thought perhaps that second one - {fileID: 0} was throwing up the warning incorrectly, so I removed it. There was no effect, I still get warnings about Ghoul Attack. So given that the only state I know of with that name does in fact have motion, what is this warning actually trying to tell me?

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• isometric background that covers the viewport [on hold]

  - by Richard

  The background image should cover the viewport. The technique I use now is a loop with an innerloop that draws diamond shaped images on a canvas element, but it looks like a rotated square. This is a nice example: ,that covers the whole viewport. I have heard something about clickthrough maps, but what more ways are there that are most efficient with mobile devices and javascript? Any advice in grid design out there?.

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• Is chess-like AI really inapplicable in turn-based strategy games?

  - by Joh

  Obviously, trying to apply the min-max algorithm on the complete tree of moves works only for small games (I apologize to all chess enthusiasts, by "small" I do not mean "simplistic"). For typical turn-based strategy games where the board is often wider than 100 tiles and all pieces in a side can move simultaneously, the min-max algorithm is inapplicable. I was wondering if a partial min-max algorithm which limits itself to N board configurations at each depth couldn't be good enough? Using a genetic algorithm, it might be possible to find a number of board configurations that are good wrt to the evaluation function. Hopefully, these configurations might also be good wrt to long-term goals. I would be surprised if this hasn't been thought of before and tried. Has it? How does it work?

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• Queries regarding Geometry Shaders

  - by maverick9888

  I am dealing with geometry shaders using GL_ARB_geometry_shader4 extension. My code goes like : GLfloat vertices[] = { 0.5,0.25,1.0, 0.5,0.75,1.0, -0.5,0.75,1.0, -0.5,0.25,1.0, 0.6,0.35,1.0, 0.6,0.85,1.0, -0.6,0.85,1.0, -0.6,0.35,1.0 }; glProgramParameteriEXT(psId, GL_GEOMETRY_INPUT_TYPE_EXT, GL_TRIANGLES); glProgramParameteriEXT(psId, GL_GEOMETRY_OUTPUT_TYPE_EXT, GL_TRIANGLE_STRIP); glLinkProgram(psId); glBindAttribLocation(psId,0,"Position"); glEnableVertexAttribArray (0); glVertexAttribPointer(0, 3, GL_FLOAT, 0, 0, vertices); glDrawArrays(GL_TRIANGLE_STRIP,0,4); My vertex shader is : #version 150 in vec3 Position; void main() { gl_Position = vec4(Position,1.0); } Geometry shader is : #version 150 #extension GL_EXT_geometry_shader4 : enable in vec4 pos[3]; void main() { int i; vec4 vertex; gl_Position = pos[0]; EmitVertex(); gl_Position = pos[1]; EmitVertex(); gl_Position = pos[2]; EmitVertex(); gl_Position = pos[0] + vec4(0.3,0.0,0.0,0.0); EmitVertex(); EndPrimitive(); } Nothing is rendered with this code. What exactly should be the mode in glDrawArrays() ? How does the GL_GEOMETRY_OUTPUT_TYPE_EXT parameter will affect glDrawArrays() ? What I expect is 3 vertices will be passed on to Geometry Shader and using those we construct a primitive of size 4 (assuming GL_TRIANGLE_STRIP requires 4 vertices). Can somebody please throw some light on this ?

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• Map and fill texture using PBO (OpenGL 3.3)

  - by NtscCobalt

  I'm learning OpenGL 3.3 trying to do the following (as it is done in D3D)... Create Texture of Width, Height, Pixel Format Map texture memory Loop write pixels Unmap texture memory Set Texture Render Right now though it renders as if the entire texture is black. I can't find a reliable source for information on how to do this though. Almost every tutorial I've found just uses glTexSubImage2D and passes a pointer to memory. Here is basically what my code does... (In this case it is generating an 1-byte Alpha Only texture but it is rendering it as the red channel for debugging) GLuint pixelBufferID; glGenBuffers(1, &pixelBufferID); glBindBuffer(GL_PIXEL_UNPACK_BUFFER, pixelBufferID); glBufferData(GL_PIXEL_UNPACK_BUFFER, 512 * 512 * 1, nullptr, GL_STREAM_DRAW); glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0); GLuint textureID; glGenTextures(1, &textureID); glBindTexture(GL_TEXTURE_2D, textureID); glTexImage2D(GL_TEXTURE_2D, 0, GL_R8, 512, 512, 0, GL_RED, GL_UNSIGNED_BYTE, nullptr); glBindTexture(GL_TEXTURE_2D, 0); glBindTexture(GL_TEXTURE_2D, textureID); glBindBuffer(GL_PIXEL_UNPACK_BUFFER, pixelBufferID); void *Memory = glMapBuffer(GL_PIXEL_UNPACK_BUFFER, GL_WRITE_ONLY); // Memory copied here, I know this is valid because it is the same loop as in my working D3D version glUnmapBuffer(GL_PIXEL_UNPACK_BUFFER); glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0); And then here is the render loop. // This chunk left in for completeness glUseProgram(glProgramId); glBindVertexArray(glVertexArrayId); glBindBuffer(GL_ARRAY_BUFFER, glVertexBufferId); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 20, 0); glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 20, 12); GLuint transformLocationID = glGetUniformLocation(3, 'transform'); glUniformMatrix4fv(transformLocationID , 1, true, somematrix) // Not sure if this is all I need to do glBindTexture(GL_TEXTURE_2D, pTex->glTextureId); GLuint textureLocationID = glGetUniformLocation(glProgramId, "texture"); glUniform1i(textureLocationID, 0); glDrawArrays(GL_TRIANGLES, Offset*3, Triangles*3); Vertex Shader #version 330 core in vec3 Position; in vec2 TexCoords; out vec2 TexOut; uniform mat4 transform; void main() { TexOut = TexCoords; gl_Position = vec4(Position, 1.0) * transform; } Pixel Shader #version 330 core uniform sampler2D texture; in vec2 TexCoords; out vec4 fragColor; void main() { // Output color fragColor.r = texture2D(texture, TexCoords).r; fragColor.g = 0.0f; fragColor.b = 0.0f; fragColor.a = 1.0; }

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• Convex Hull for Concave Objects

  - by Lighthink

  I want to implement GJK and I want it to handle concave shapes too (almost all my shapes are concave). I've thought of decomposing the concave shape into convex shapes and then building a hierarchical tree out of convex shapes, but I do not know how to do it. Nothing I could find on the Internet about it wasn't satisfying my needs, so maybe someone can point me in the right direction or give a full explanation.

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• Per-pixel displacement mapping GLSL

  - by Chris

  Im trying to implement a per-pixel displacement shader in GLSL. I read through several papers and "tutorials" I found and ended up with trying to implement the approach NVIDIA used in their Cascade Demo (http://www.slideshare.net/icastano/cascades-demo-secrets) starting at Slide 82. At the moment I am completly stuck with following problem: When I am far away the displacement seems to work. But as more I move closer to my surface, the texture gets bent in x-axis and somehow it looks like there is a little bent in general in one direction. EDIT: I added a video: click I added some screen to illustrate the problem: Well I tried lots of things already and I am starting to get a bit frustrated as my ideas run out. I added my full VS and FS code: VS: #version 400 layout(location = 0) in vec3 IN_VS_Position; layout(location = 1) in vec3 IN_VS_Normal; layout(location = 2) in vec2 IN_VS_Texcoord; layout(location = 3) in vec3 IN_VS_Tangent; layout(location = 4) in vec3 IN_VS_BiTangent; uniform vec3 uLightPos; uniform vec3 uCameraDirection; uniform mat4 uViewProjection; uniform mat4 uModel; uniform mat4 uView; uniform mat3 uNormalMatrix; out vec2 IN_FS_Texcoord; out vec3 IN_FS_CameraDir_Tangent; out vec3 IN_FS_LightDir_Tangent; void main( void ) { IN_FS_Texcoord = IN_VS_Texcoord; vec4 posObject = uModel * vec4(IN_VS_Position, 1.0); vec3 normalObject = (uModel * vec4(IN_VS_Normal, 0.0)).xyz; vec3 tangentObject = (uModel * vec4(IN_VS_Tangent, 0.0)).xyz; //vec3 binormalObject = (uModel * vec4(IN_VS_BiTangent, 0.0)).xyz; vec3 binormalObject = normalize(cross(tangentObject, normalObject)); // uCameraDirection is the camera position, just bad named vec3 fvViewDirection = normalize( uCameraDirection - posObject.xyz); vec3 fvLightDirection = normalize( uLightPos.xyz - posObject.xyz ); IN_FS_CameraDir_Tangent.x = dot( tangentObject, fvViewDirection ); IN_FS_CameraDir_Tangent.y = dot( binormalObject, fvViewDirection ); IN_FS_CameraDir_Tangent.z = dot( normalObject, fvViewDirection ); IN_FS_LightDir_Tangent.x = dot( tangentObject, fvLightDirection ); IN_FS_LightDir_Tangent.y = dot( binormalObject, fvLightDirection ); IN_FS_LightDir_Tangent.z = dot( normalObject, fvLightDirection ); gl_Position = (uViewProjection*uModel) * vec4(IN_VS_Position, 1.0); } The VS just builds the TBN matrix, from incoming normal, tangent and binormal in world space. Calculates the light and eye direction in worldspace. And finally transforms the light and eye direction into tangent space. FS: #version 400 // uniforms uniform Light { vec4 fvDiffuse; vec4 fvAmbient; vec4 fvSpecular; }; uniform Material { vec4 diffuse; vec4 ambient; vec4 specular; vec4 emissive; float fSpecularPower; float shininessStrength; }; uniform sampler2D colorSampler; uniform sampler2D normalMapSampler; uniform sampler2D heightMapSampler; in vec2 IN_FS_Texcoord; in vec3 IN_FS_CameraDir_Tangent; in vec3 IN_FS_LightDir_Tangent; out vec4 color; vec2 TraceRay(in float height, in vec2 coords, in vec3 dir, in float mipmap){ vec2 NewCoords = coords; vec2 dUV = - dir.xy * height * 0.08; float SearchHeight = 1.0; float prev_hits = 0.0; float hit_h = 0.0; for(int i=0;i<10;i++){ SearchHeight -= 0.1; NewCoords += dUV; float CurrentHeight = textureLod(heightMapSampler,NewCoords.xy, mipmap).r; float first_hit = clamp((CurrentHeight - SearchHeight - prev_hits) * 499999.0,0.0,1.0); hit_h += first_hit * SearchHeight; prev_hits += first_hit; } NewCoords = coords + dUV * (1.0-hit_h) * 10.0f - dUV; vec2 Temp = NewCoords; SearchHeight = hit_h+0.1; float Start = SearchHeight; dUV *= 0.2; prev_hits = 0.0; hit_h = 0.0; for(int i=0;i<5;i++){ SearchHeight -= 0.02; NewCoords += dUV; float CurrentHeight = textureLod(heightMapSampler,NewCoords.xy, mipmap).r; float first_hit = clamp((CurrentHeight - SearchHeight - prev_hits) * 499999.0,0.0,1.0); hit_h += first_hit * SearchHeight; prev_hits += first_hit; } NewCoords = Temp + dUV * (Start - hit_h) * 50.0f; return NewCoords; } void main( void ) { vec3 fvLightDirection = normalize( IN_FS_LightDir_Tangent ); vec3 fvViewDirection = normalize( IN_FS_CameraDir_Tangent ); float mipmap = 0; vec2 NewCoord = TraceRay(0.1,IN_FS_Texcoord,fvViewDirection,mipmap); //vec2 ddx = dFdx(NewCoord); //vec2 ddy = dFdy(NewCoord); vec3 BumpMapNormal = textureLod(normalMapSampler, NewCoord.xy, mipmap).xyz; BumpMapNormal = normalize(2.0 * BumpMapNormal - vec3(1.0, 1.0, 1.0)); vec3 fvNormal = BumpMapNormal; float fNDotL = dot( fvNormal, fvLightDirection ); vec3 fvReflection = normalize( ( ( 2.0 * fvNormal ) * fNDotL ) - fvLightDirection ); float fRDotV = max( 0.0, dot( fvReflection, fvViewDirection ) ); vec4 fvBaseColor = textureLod( colorSampler, NewCoord.xy,mipmap); vec4 fvTotalAmbient = fvAmbient * fvBaseColor; vec4 fvTotalDiffuse = fvDiffuse * fNDotL * fvBaseColor; vec4 fvTotalSpecular = fvSpecular * ( pow( fRDotV, fSpecularPower ) ); color = ( fvTotalAmbient + (fvTotalDiffuse + fvTotalSpecular) ); } The FS implements the displacement technique in TraceRay method, while always using mipmap level 0. Most of the code is from NVIDIA sample and another paper I found on the web, so I guess there cannot be much wrong in here. At the end it uses the modified UV coords for getting the displaced normal from the normal map and the color from the color map. I looking forward for some ideas. Thanks in advance! Edit: Here is the code loading the heightmap: glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, mWidth, mHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, mImageData); glGenerateMipmap(GL_TEXTURE_2D); //glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR_MIPMAP_LINEAR); //glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR); //glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); //glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); Maybe something wrong in here?

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• Pixel alignment algorithm

  - by user42325

  I have a set of square blocks, I want to draw them in a window. I am sure the coordinates calculation is correct. But on the screen, some squares' edge overlap with other, some are not. I remember the problem is caused by accuracy of pixels. I remember there's a specific topic related to this kind of problem in 2D image rendering. But I don't remember what exactly it is, and how to solve it. Look at this screenshot. Each block should have a fixed width margin. But in the image, the vertical white line have different width.Though, the horizontal lines looks fine.

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• Space-efficient data structures for broad-phase collision detection

  - by Marian Ivanov

  As far as I know, these are three types of data structures that can be used for collision detection broadphase: Unsorted arrays: Check every object againist every object - O(n^2) time; O(log n) space. It's so slow, it's useless if n isn't really small. for (i=1;i<objects;i++){ for(j=0;j<i;j++) narrowPhase(i,j); }; Sorted arrays: Sort the objects, so that you get O(n^(2-1/k)) for k dimensions O(n^1.5) for 2d and O(n^1.67) for 3d and O(n) space. Assuming the space is 2D and sortedArray is sorted so that if the object begins in sortedArray[i] and another object ends at sortedArray[i-1]; they don't collide Heaps of stacks: Divide the objects between a heap of stacks, so that you only have to check the bucket, its children and its parents - O(n log n) time, but O(n^2) space. This is probably the most frequently used approach. Is there a way of having O(n log n) time with less space? When is it more efficient to use sorted arrays over heaps and vice versa?

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• SDL_BlitSurface segmentation fault (surfaces aren't null)

  - by Trollkemada

  My app is crashing on SDL_BlitSurface() and i can't figure out why. I think it has something to do with my static object. If you read the code you'll why I think so. This happens when the limits of the map are reached, i.e. (iwidth || jheight). This is the code: Map.cpp (this render) Tile const * Map::getTyle(int i, int j) const { if (i >= 0 && j >= 0 && i < width && j < height) { return data[i][j]; } else { return &Tile::ERROR_TYLE; // This makes SDL_BlitSurface (called later) crash //return new Tile(TileType::ERROR); // This works with not problem (but is memory leak, of course) } } void Map::render(int x, int y, int width, int height) const { //DEBUG("(Rendering...) x: "<<x<<", y: "<<y<<", width: "<<width<<", height: "<<height); int firstI = x / TileType::PIXEL_PER_TILE; int firstJ = y / TileType::PIXEL_PER_TILE; int lastI = (x+width) / TileType::PIXEL_PER_TILE; int lastJ = (y+height) / TileType::PIXEL_PER_TILE; // The previous integer division rounds down when dealing with positive values, but it rounds up // negative values. This is a fix for that (We need those values always rounded down) if (firstI < 0) { firstI--; } if (firstJ < 0) { firstJ--; } const int firstX = x; const int firstY = y; SDL_Rect srcRect; SDL_Rect dstRect; for (int i=firstI; i <= lastI; i++) { for (int j=firstJ; j <= lastJ; j++) { if (i*TileType::PIXEL_PER_TILE < x) { srcRect.x = x % TileType::PIXEL_PER_TILE; srcRect.w = TileType::PIXEL_PER_TILE - (x % TileType::PIXEL_PER_TILE); dstRect.x = i*TileType::PIXEL_PER_TILE + (x % TileType::PIXEL_PER_TILE) - firstX; } else if (i*TileType::PIXEL_PER_TILE >= x + width) { srcRect.x = 0; srcRect.w = x % TileType::PIXEL_PER_TILE; dstRect.x = i*TileType::PIXEL_PER_TILE - firstX; } else { srcRect.x = 0; srcRect.w = TileType::PIXEL_PER_TILE; dstRect.x = i*TileType::PIXEL_PER_TILE - firstX; } if (j*TileType::PIXEL_PER_TILE < y) { srcRect.y = 0; srcRect.h = TileType::PIXEL_PER_TILE - (y % TileType::PIXEL_PER_TILE); dstRect.y = j*TileType::PIXEL_PER_TILE + (y % TileType::PIXEL_PER_TILE) - firstY; } else if (j*TileType::PIXEL_PER_TILE >= y + height) { srcRect.y = y % TileType::PIXEL_PER_TILE; srcRect.h = y % TileType::PIXEL_PER_TILE; dstRect.y = j*TileType::PIXEL_PER_TILE - firstY; } else { srcRect.y = 0; srcRect.h = TileType::PIXEL_PER_TILE; dstRect.y = j*TileType::PIXEL_PER_TILE - firstY; } SDL::YtoSDL(dstRect.y, srcRect.h); SDL_BlitSurface(getTyle(i,j)->getType()->getSurface(), &srcRect, SDL::getScreen(), &dstRect); // <-- Crash HERE /*DEBUG("i = "<<i<<", j = "<<j); DEBUG("srcRect.x = "<<srcRect.x<<", srcRect.y = "<<srcRect.y<<", srcRect.w = "<<srcRect.w<<", srcRect.h = "<<srcRect.h); DEBUG("dstRect.x = "<<dstRect.x<<", dstRect.y = "<<dstRect.y);*/ } } } Tile.h #ifndef TILE_H #define TILE_H #include "TileType.h" class Tile { private: TileType const * type; public: static const Tile ERROR_TYLE; Tile(TileType const * t); ~Tile(); TileType const * getType() const; }; #endif Tile.cpp #include "Tile.h" const Tile Tile::ERROR_TYLE(TileType::ERROR); Tile::Tile(TileType const * t) : type(t) {} Tile::~Tile() {} TileType const * Tile::getType() const { return type; } TileType.h #ifndef TILETYPE_H #define TILETYPE_H #include "SDL.h" #include "DEBUG.h" class TileType { protected: TileType(); ~TileType(); public: static const int PIXEL_PER_TILE = 30; static const TileType * ERROR; static const TileType * AIR; static const TileType * SOLID; virtual SDL_Surface * getSurface() const = 0; virtual bool isSolid(int x, int y) const = 0; }; #endif ErrorTyle.h #ifndef ERRORTILE_H #define ERRORTILE_H #include "TileType.h" class ErrorTile : public TileType { friend class TileType; private: ErrorTile(); mutable SDL_Surface * surface; static const char * FILE_PATH; public: SDL_Surface * getSurface() const; bool isSolid(int x, int y) const ; }; #endif ErrorTyle.cpp (The surface can't be loaded when building the object, because it is a static object and SDL_Init() needs to be called first) #include "ErrorTile.h" const char * ErrorTile::FILE_PATH = ("C:\\error.bmp"); ErrorTile::ErrorTile() : TileType(), surface(NULL) {} SDL_Surface * ErrorTile::getSurface() const { if (surface == NULL) { if (SDL::isOn()) { surface = SDL::loadAndOptimice(ErrorTile::FILE_PATH); if (surface->w != TileType::PIXEL_PER_TILE || surface->h != TileType::PIXEL_PER_TILE) { WARNING("Bad tile surface size"); } } else { ERROR("Trying to load a surface, but SDL is not on"); } } if (surface == NULL) { // This if doesn't get called, so surface != NULL ERROR("WTF? Can't load surface :\\"); } return surface; } bool ErrorTile::isSolid(int x, int y) const { return true; }

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• Stencil buffer appears to not be decrementing values correctly

  - by Alex Ames

  I'm attempting to use the stencil buffer as a clipper for my UI system, but I'm having trouble debugging a problem I'm running in to. This is what I'm doing: A widget can pass a rectangle to the the stencil clipper functions, which will increment the stencil buffer values that it covers. Then it will draw its children, which will only get drawn in the stencilled area (so that if they extend outside they'll be clipped). After a widget is done drawing its children, it pops that rectangle from the stack and in the process decrements the values in the stencil buffer that it has previously incremented. The slightly simplified code is below: static void drawStencil(Rect& rect, unsigned int ref) { // Save previous values of the color and depth masks GLboolean colorMask[4]; GLboolean depthMask; glGetBooleanv(GL_COLOR_WRITEMASK, colorMask); glGetBooleanv(GL_DEPTH_WRITEMASK, &depthMask); // Turn off drawing glColorMask(0, 0, 0, 0); glDepthMask(0); // Draw vertices here ... // Turn everything back on glColorMask(colorMask[0], colorMask[1], colorMask[2], colorMask[3]); glDepthMask(depthMask); // Only render pixels in areas where the stencil buffer value == ref glStencilFunc(GL_EQUAL, ref, 0xFF); glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP); } void pushScissor(Rect rect) { // increment things only at the current stencil stack level glStencilFunc(GL_EQUAL, s_scissorStack.size(), 0xFF); glStencilOp(GL_KEEP, GL_INCR, GL_INCR); s_scissorStack.push_back(rect); drawStencil(rect, states, s_ScissorStack.size()); } void popScissor() { // undo what was done in the previous push, // decrement things only at the current stencil stack level glStencilFunc(GL_EQUAL, s_scissorStack.size(), 0xFF); glStencilOp(GL_KEEP, GL_DECR, GL_DECR); Rect rect = s_scissorStack.back(); s_scissorStack.pop_back(); drawStencil(rect, states, s_scissorStack.size()); } And this is how it's being used by the Widgets if (m_clip) pushScissor(m_rect); drawInternal(target, states); for (auto child : m_children) target.draw(*child, states); if (m_clip) popScissor(); This is the result of the above code: There are two things on the screen, a giant test button, and a window with some buttons and text areas on it. The text area scroll box is set to clip its children (so that the text doesn't extend outside the scroll box). The button is drawn after the window and should be on top of it completely. However, for some reason the text area is appearing on top of the button. The only reason I can think of that this would happen is if the stencil values were not getting decremented in the pop, and when it comes time to render the button, since those pixels don't have the right stencil value it doesn't draw over. But I can't figure out whats wrong with my code that would cause that to happen.

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• Should I always be checking every neighbor when building voxel meshes?

  - by Raven Dreamer

  I've been playing around with Unity3d, seeing if I can make a voxel-based engine out of it (a la Castle Story, or Minecraft). I've dynamically built a mesh from a volume of cubes, and now I'm looking into reducing the number of vertices built into each mesh, as right now, I'm "rendering" vertices and triangles for cubes that are fully hidden within the larger voxel volume. The simple solution is to check each of the 6 directions for each cube, and only add the face to the mesh if the neighboring voxel in that direction is "empty". Parsing a voxel volume is BigO(N^3), and checking the 6 neighbors keeps it BigO(7*N^3)-BigO(N^3). The one thing this results in is a lot of redundant calls, as the same voxel will be polled up to 7 times, just to build the mesh. My question, then, is: Is there a way to parse a cubic volume (and find which faces have neighbors) with fewer redundant calls? And perhaps more importantly, does it matter (as BigO complexity is the same in both cases)?

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• 3D/perspective Top down shooter bullet issues

  - by Tseng

  I'm developing a top-down shooter with multiple levels (ground for ground units, middle level for buildings, top level for air unity). The problem is the collision. Though I can make the collider box of a bullet be long enough to reach the ground (and collide with it), the real issue is optical. When the bullet is fired from a aircraft and collides with some object on the ground (building, ground unit) it will be optically offset due to the perspective camera, because it looks like the shot "by-passed" the target as seen below Is there any way to make the bullets collide perspectively correct? I'm using Unity3d Engine and it offers only simple colliders (box, sphere, cylinder, mesh and wheel), though I don't think a cone-formed collider would solve this issue. I'd need a (cheap) way to check if it's overlapping a destructible object? I thought of casting a ray from the camera through the bullet and if it hits something destructible, trigger an action, but that's quite punctual and maybe to performance heavy on certain number of bullets

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• What causes Box2D revolute joints to separate?

  - by nbolton

  I have created a rag doll using dynamic bodies (rectangles) and simple revolute joints (with lower and upper angles). When my rag doll hits the ground (which is a static body) the bodies seem to fidget and the joints separate. It looks like the bodies are sticking to the ground, and the momentum of the rag doll pulls the joint apart (see screenshot below). I'm not sure if it's related, but I'm using the Badlogic GDX Java wrapper for Box2D. Here's some snippets of what I think is the most relevant code: private RevoluteJoint joinBodyParts( Body a, Body b, Vector2 anchor, float lowerAngle, float upperAngle) { RevoluteJointDef jointDef = new RevoluteJointDef(); jointDef.initialize(a, b, a.getWorldPoint(anchor)); jointDef.enableLimit = true; jointDef.lowerAngle = lowerAngle; jointDef.upperAngle = upperAngle; return (RevoluteJoint)world.createJoint(jointDef); } private Body createRectangleBodyPart( float x, float y, float width, float height) { PolygonShape shape = new PolygonShape(); shape.setAsBox(width, height); BodyDef bodyDef = new BodyDef(); bodyDef.type = BodyType.DynamicBody; bodyDef.position.y = y; bodyDef.position.x = x; Body body = world.createBody(bodyDef); FixtureDef fixtureDef = new FixtureDef(); fixtureDef.shape = shape; fixtureDef.density = 10; fixtureDef.filter.groupIndex = -1; fixtureDef.filter.categoryBits = FILTER_BOY; fixtureDef.filter.maskBits = FILTER_STUFF | FILTER_WALL; body.createFixture(fixtureDef); shape.dispose(); return body; } I've skipped the method for creating the head, as it's pretty much the same as the rectangle method (just using a cricle shape). Those methods are used like so: torso = createRectangleBodyPart(x, y + 5, 0.25f, 1.5f); Body head = createRoundBodyPart(x, y + 7.4f, 1); Body leftLegTop = createRectangleBodyPart(x, y + 2.7f, 0.25f, 1); Body rightLegTop = createRectangleBodyPart(x, y + 2.7f, 0.25f, 1); Body leftLegBottom = createRectangleBodyPart(x, y + 1, 0.25f, 1); Body rightLegBottom = createRectangleBodyPart(x, y + 1, 0.25f, 1); Body leftArm = createRectangleBodyPart(x, y + 5, 0.25f, 1.2f); Body rightArm = createRectangleBodyPart(x, y + 5, 0.25f, 1.2f); joinBodyParts(torso, head, new Vector2(0, 1.6f), headAngle); leftLegTopJoint = joinBodyParts(torso, leftLegTop, new Vector2(0, -1.2f), 0.1f, legAngle); rightLegTopJoint = joinBodyParts(torso, rightLegTop, new Vector2(0, -1.2f), 0.1f, legAngle); leftLegBottomJoint = joinBodyParts(leftLegTop, leftLegBottom, new Vector2(0, -1), -legAngle * 1.5f, 0); rightLegBottomJoint = joinBodyParts(rightLegTop, rightLegBottom, new Vector2(0, -1), -legAngle * 1.5f, 0); leftArmJoint = joinBodyParts(torso, leftArm, new Vector2(0, 1), -armAngle * 0.7f, armAngle); rightArmJoint = joinBodyParts(torso, rightArm, new Vector2(0, 1), -armAngle * 0.7f, armAngle);

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• Changing State in PlayerControler from PlayerInput

  - by Jeremy Talus

  In my player input I wanna change the the "State" of my player controller but I have some trouble to do it my player input is declared like that : class ResistancePlayerInput extends PlayerInput within ResistancePlayerController config(ResistancePlayerInput); and in my playerControler I have that : class ResistancePlayerController extends GamePlayerController; var name PreviousState; DefaultProperties { CameraClass = class 'ResistanceCamera' //Telling the player controller to use your custom camera script InputClass = class'ResistanceGame.ResistancePlayerInput' DefaultFOV = 90.f //Telling the player controller what the default field of view (FOV) should be } simulated event PostBeginPlay() { Super.PostBeginPlay(); } auto state Walking { event BeginState(name PreviousStateName) { Pawn.GroundSpeed = 200; `log("Player Walking"); } } state Running extends Walking { event BeginState(name PreviousStateName) { Pawn.GroundSpeed = 350; `log("Player Running"); } } state Sprinting extends Walking { event BeginState(name PreviousStateName) { Pawn.GroundSpeed = 800; `log("Player Sprinting"); } } I have tried to use PCOwner.GotoState(); and ResistancePlayerController(PCOwner).GotoState(); but won't work. I have also tried a simple GotoState, and nothing happen how can I call GotoState for the PC Class from my player input ?

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• Detecting if an object is following a path

  - by justin.m.chase

  I am attempting to take GPS data and track it on a map and see if it follows a given path. I have the path as a set of points and the GPS data streams in as a similar set of points. I am attempting to track the progression of the current position across the path and I am wondering if there are any well known algorithms for this. I have come up with my own that works ok but it is a complex enough problem that I would like to minimize the amount of re-inventing of the wheel that I do. What approach or algorithm would you recommend taking for this problem?

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• Transforming a primitive tetrahedron into a primitive icosahedron?

  - by Djentleman

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

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• Unexpected results for projection on to plane

  - by ravenspoint

  I want to use this projection matrix: GLfloat shadow[] = { -1,0,0,0, 1,0,-1,1, 0,0,-1,0, 0,0,0,-1 }; It should cast object shadows onto the y = 0 plane from a point light at 1,1,-1. I create a rectangle in the x = 0.5 plane glBegin( GL_QUADS ); glVertex3f( 0.5,0.2,-0.5); glVertex3f( 0.5,0.2,-1.5); glVertex3f( 0.5,0.5,-1.5); glVertex3f( 0.5,0.5,-0.5); glEnd(); Now if I manually multiply these vertices with the matrix, I get. glBegin( GL_QUADS ); glVertex3f( 0.375,0,-0.375); glVertex3f( 0.375,0,-1.625); glVertex3f( 0,0,-2); glVertex3f( 0,0,0); glEnd(); Which produces a reasonable display ( camera at 0,5,0 looking down y axis ) So rather than do the calculation manually, I should be able to use the opengl model transormation. I write this code: glMatrixMode (GL_MODELVIEW); GLfloat shadow[] = { -1,0,0,0, 1,0,-1,1, 0,0,-1,0, 0,0,0,-1 }; glLoadMatrixf( shadow ); glBegin( GL_QUADS ); glVertex3f( 0.5,0.2,-0.5); glVertex3f( 0.5,0.2,-1.5); glVertex3f( 0.5,0.5,-1.5); glVertex3f( 0.5,0.5,-0.5); glEnd(); But this produces a blank screen! What am I doing wrong? Is there some debug mode where I can print out the transformed vertices, so I can see where they are ending up? Note: People have suggested that using glMultMatrixf() might make a difference. It doesn't. Replacing glLoadMatrixf( shadow ); with glLoadIdentity(); glMultMatrixf( shadow ); gives the identical result ( of course! )

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• UV Atlas Generation and Seam Removal

  - by P. Avery

  I'm generating light maps for scene mesh objects using DirectX's UV Atlas Tool( D3DXUVAtlasCreate() ). I've succeeded in generating an atlas, however, when I try to render the mesh object using the atlas the seams are visible on the mesh. Below are images of a lightmap generated for a cube. Here is the code I use to generate a uv atlas for a cube: struct sVertexPosNormTex { D3DXVECTOR3 vPos, vNorm; D3DXVECTOR2 vUV; sVertexPosNormTex(){} sVertexPosNormTex( D3DXVECTOR3 v, D3DXVECTOR3 n, D3DXVECTOR2 uv ) { vPos = v; vNorm = n; vUV = uv; } ~sVertexPosNormTex() { } }; // create a light map texture to fill programatically hr = D3DXCreateTexture( pd3dDevice, 128, 128, 1, 0, D3DFMT_A8R8G8B8, D3DPOOL_MANAGED, &pLightmap ); if( FAILED( hr ) ) { DebugStringDX( "Main", "Failed to D3DXCreateTexture( lightmap )", __LINE__, hr ); return hr; } // get the zero level surface from the texture IDirect3DSurface9 *pS = NULL; pLightmap->GetSurfaceLevel( 0, &pS ); // clear surface pd3dDevice->ColorFill( pS, NULL, D3DCOLOR_XRGB( 0, 0, 0 ) ); // load a sample mesh DWORD dwcMaterials = 0; LPD3DXBUFFER pMaterialBuffer = NULL; V_RETURN( D3DXLoadMeshFromX( L"cube3.x", D3DXMESH_MANAGED, pd3dDevice, &pAdjacency, &pMaterialBuffer, NULL, &dwcMaterials, &g_pMesh ) ); // generate adjacency DWORD *pdwAdjacency = new DWORD[ 3 * g_pMesh->GetNumFaces() ]; g_pMesh->GenerateAdjacency( 1e-6f, pdwAdjacency ); // create light map coordinates LPD3DXMESH pMesh = NULL; LPD3DXBUFFER pFacePartitioning = NULL, pVertexRemapArray = NULL; FLOAT resultStretch = 0; UINT numCharts = 0; hr = D3DXUVAtlasCreate( g_pMesh, 0, 0, 128, 128, 3.5f, 0, pdwAdjacency, NULL, NULL, NULL, NULL, NULL, 0, &pMesh, &pFacePartitioning, &pVertexRemapArray, &resultStretch, &numCharts ); if( SUCCEEDED( hr ) ) { // release and set mesh SAFE_RELEASE( g_pMesh ); g_pMesh = pMesh; // write mesh to file hr = D3DXSaveMeshToX( L"cube4.x", g_pMesh, 0, ( const D3DXMATERIAL* )pMaterialBuffer->GetBufferPointer(), NULL, dwcMaterials, D3DXF_FILEFORMAT_TEXT ); if( FAILED( hr ) ) { DebugStringDX( "Main", "Failed to D3DXSaveMeshToX() at OnD3D9CreateDevice()", __LINE__, hr ); } // fill the the light map hr = BuildLightmap( pS, g_pMesh ); if( FAILED( hr ) ) { DebugStringDX( "Main", "Failed to BuildLightmap()", __LINE__, hr ); } } else { DebugStringDX( "Main", "Failed to D3DXUVAtlasCreate() at OnD3D9CreateDevice()", __LINE__, hr ); } SAFE_RELEASE( pS ); SAFE_DELETE_ARRAY( pdwAdjacency ); SAFE_RELEASE( pFacePartitioning ); SAFE_RELEASE( pVertexRemapArray ); SAFE_RELEASE( pMaterialBuffer ); Here is code to fill lightmap texture: HRESULT BuildLightmap( IDirect3DSurface9 *pS, LPD3DXMESH pMesh ) { HRESULT hr = S_OK; // validate lightmap texture surface and mesh if( !pS || !pMesh ) return E_POINTER; // lock the mesh vertex buffer sVertexPosNormTex *pV = NULL; pMesh->LockVertexBuffer( D3DLOCK_READONLY, ( void** )&pV ); // lock the mesh index buffer WORD *pI = NULL; pMesh->LockIndexBuffer( D3DLOCK_READONLY, ( void** )&pI ); // get the lightmap texture surface description D3DSURFACE_DESC desc; pS->GetDesc( &desc ); // lock the surface rect to fill with color data D3DLOCKED_RECT rct; hr = pS->LockRect( &rct, NULL, 0 ); if( FAILED( hr ) ) { DebugStringDX( "main.cpp:", "Failed to IDirect3DTexture9::LockRect()", __LINE__, hr ); return hr; } // iterate the pixels of the lightmap texture // check each pixel to see if it lies between the uv coordinates of a cube face BYTE *pBuffer = ( BYTE* )rct.pBits; for( UINT y = 0; y < desc.Height; ++y ) { BYTE* pBufferRow = ( BYTE* )pBuffer; for( UINT x = 0; x < desc.Width * 4; x+=4 ) { // determine the pixel's uv coordinate D3DXVECTOR2 p( ( ( float )x / 4.0f ) / ( float )desc.Width + 0.5f / 128.0f, y / ( float )desc.Height + 0.5f / 128.0f ); // for each face of the mesh // check to see if the pixel lies within the face's uv coordinates for( UINT i = 0; i < 3 * pMesh->GetNumFaces(); i +=3 ) { sVertexPosNormTex v[ 3 ]; v[ 0 ] = pV[ pI[ i + 0 ] ]; v[ 1 ] = pV[ pI[ i + 1 ] ]; v[ 2 ] = pV[ pI[ i + 2 ] ]; if( TexcoordIsWithinBounds( v[ 0 ].vUV, v[ 1 ].vUV, v[ 2 ].vUV, p ) ) { // the pixel lies b/t the uv coordinates of a cube face // light contribution functions aren't needed yet //D3DXVECTOR3 vPos = TexcoordToPos( v[ 0 ].vPos, v[ 1 ].vPos, v[ 2 ].vPos, v[ 0 ].vUV, v[ 1 ].vUV, v[ 2 ].vUV, p ); //D3DXVECTOR3 vNormal = v[ 0 ].vNorm; // set the color of this pixel red( for demo ) BYTE ba[] = { 0, 0, 255, 255, }; //ComputeContribution( vPos, vNormal, g_sLight, ba ); // copy the byte array into the light map texture memcpy( ( void* )&pBufferRow[ x ], ( void* )ba, 4 * sizeof( BYTE ) ); } } } // go to next line of the texture pBuffer += rct.Pitch; } // unlock the surface rect pS->UnlockRect(); // unlock mesh vertex and index buffers pMesh->UnlockIndexBuffer(); pMesh->UnlockVertexBuffer(); // write the surface to file hr = D3DXSaveSurfaceToFile( L"LightMap.jpg", D3DXIFF_JPG, pS, NULL, NULL ); if( FAILED( hr ) ) DebugStringDX( "Main.cpp", "Failed to D3DXSaveSurfaceToFile()", __LINE__, hr ); return hr; } bool TexcoordIsWithinBounds( const D3DXVECTOR2 &t0, const D3DXVECTOR2 &t1, const D3DXVECTOR2 &t2, const D3DXVECTOR2 &p ) { // compute vectors D3DXVECTOR2 v0 = t1 - t0, v1 = t2 - t0, v2 = p - t0; float f00 = D3DXVec2Dot( &v0, &v0 ); float f01 = D3DXVec2Dot( &v0, &v1 ); float f02 = D3DXVec2Dot( &v0, &v2 ); float f11 = D3DXVec2Dot( &v1, &v1 ); float f12 = D3DXVec2Dot( &v1, &v2 ); // Compute barycentric coordinates float invDenom = 1 / ( f00 * f11 - f01 * f01 ); float fU = ( f11 * f02 - f01 * f12 ) * invDenom; float fV = ( f00 * f12 - f01 * f02 ) * invDenom; // Check if point is in triangle if( ( fU >= 0 ) && ( fV >= 0 ) && ( fU + fV < 1 ) ) return true; return false; } Screenshot Lightmap I believe the problem comes from the difference between the lightmap uv coordinates and the pixel center coordinates...for example, here are the lightmap uv coordinates( generated by D3DXUVAtlasCreate() ) for a specific face( tri ) within the mesh, keep in mind that I'm using the mesh uv coordinates to write the pixels for the texture: v[ 0 ].uv = D3DXVECTOR2( 0.003581, 0.295631 ); v[ 1 ].uv = D3DXVECTOR2( 0.003581, 0.003581 ); v[ 2 ].uv = D3DXVECTOR2( 0.295631, 0.003581 ); the lightmap texture size is 128 x 128 pixels. The upper-left pixel center coordinates are: float halfPixel = 0.5 / 128 = 0.00390625; D3DXVECTOR2 pixelCenter = D3DXVECTOR2( halfPixel, halfPixel ); will the mapping and sampling of the lightmap texture will require that an offset be taken into account or that the uv coordinates are snapped to the pixel centers..? ...Any ideas on the best way to approach this situation would be appreciated...What are the common practices?

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• Overriding component behavior

  - by deft_code

  I was thinking of how to implement overriding of behaviors in a component based entity system. A concrete example, an entity has a heath component that can be damaged, healed, killed etc. The entity also has an armor component that limits the amount of damage a character receives. Has anyone implemented behaviors like this in a component based system before? How did you do it? If no one has ever done this before why do you think that is. Is there anything particularly wrong headed about overriding component behaviors? Below is rough sketch up of how I imagine it would work. Components in an entity are ordered. Those at the front get a chance to service an interface first. I don't detail how that is done, just assume it uses evil dynamic_casts (it doesn't but the end effect is the same without the need for RTTI). class IHealth { public: float get_health( void ) const = 0; void do_damage( float amount ) = 0; }; class Health : public Component, public IHealth { public: void do_damage( float amount ) { m_damage -= amount; } private: float m_health; }; class Armor : public Component, public IHealth { public: float get_health( void ) const { return next<IHealth>().get_health(); } void do_damage( float amount ) { next<IHealth>().do_damage( amount / 2 ); } }; entity.add( new Health( 100 ) ); entity.add( new Armor() ); assert( entity.get<IHealth>().get_health() == 100 ); entity.get<IHealth>().do_damage( 10 ); assert( entity.get<IHealth>().get_health() == 95 ); Is there anything particularly naive about the way I'm proposing to do this?

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• Problem with Ogre::Camera lookAt function when target is directly below.

  - by PigBen

  I am trying to make a class which controls a camera. It's pretty basic right now, it looks like this: class HoveringCameraController { public: void init(Ogre::Camera & camera, AnimatedBody & target, Ogre::Real height); void update(Ogre::Real time_delta); private: Ogre::Camera * camera_; AnimatedBody * target_; Ogre::Real height_; }; HoveringCameraController.cpp void HoveringCameraController::init(Ogre::Camera & camera, AnimatedBody & target, Ogre::Real height) { camera_ = &camera; target_ = &target; height_ = height; update(0.0); } void HoveringCameraController::update(Ogre::Real time_delta) { auto position = target_->getPosition(); position.y += height_; camera_->setPosition(position); camera_->lookAt(target_->getPosition()); } AnimatedBody is just a class that encapsulates an entity, it's animations and a scene node. The getPosition function is simply forwarded to it's scene node. What I want(for now) is for the camera to simply follow the AnimatedBody overhead at the distance given(the height parameter), and look down at it. It follows the object around, but it doesn't look straight down, it's tilted quite a bit in the positive Z direction. Does anybody have any idea why it would do that? If I change this line: position.y += height_; to this: position.x += height_; or this: position.z += height_; it does exactly what I would expect. It follows the object from the side or front, and looks directly at it.

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• Simple project - make a 3D box tumble and fall to the ground [closed]

  - by Dominic Bou-Samra

  Possible Duplicate: Resources to learn programming rigid body simulation Hi guys, I want to try learning rigid-body dynamic simulation. I have done a fluid and cloth simulation before, but never anything rigid. My maths knowledge is limited in that I don't know the notation that well. Are there any good cliff-notes, tutorials, guides on how I would accomplish a simple task like this? I don't want a super complex pdf that's only a little relevant. Thanks.

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