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• Z Order in 2D with orthographic projection and texture atlas

  - by Carbon Crystal

  I am working with a 2D game in OpenGL ES and have a question about z-order together with a texture atlas. I am using an orthographic projection because I want pixel-perfect rendering of 2D sprites, however from what I can determine the draw order is really the only thing that will determine which textures (sprites) appear above or below their neighbors. That is, the "z-index" is a function of the order in which the textures are drawn as opposed to the z coordinate on the vertex array being drawn. So.. I have a texture atlas to save binding multiple textures for each draw call but this immediately creates a problem if there is more than one atlas in play. If I need to draw textures from more than one atlas (typically the case if I have too many sprites to fit in a single atlas of a reasonable size), then I can't maintain a "draw order" across atlases unless I want to bind/unbind the atlas textures more than once.. which kinda defeats the purpose. Does anyone have any clues as to what the best approach is here? Currently I'm running under an assumption that I will have to declare different fixed "depths" (e.g foreground, background etc) in my 2D scene and assume that the z-order for sprites at a given depth is the same. Then I can have as many atlases as I need at each depth and simply draw the depths in order (along with their associated atlases) I'd love to hear what other people are doing.

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• Checking if an object is inside bounds of an isometric chunk

  - by gopgop

  How would I check if an object is inside the bounds of an isometric chunk? for example I have a player and I want to check if its inside the bounds of this isometric chunk. I draw the isometric chunk's tiles using OpenGL Quads. My first try was checking in a square pattern kind of thing: e = object; this = isometric chunk; if (e.getLocation().getX() < this.getLocation().getX()+World.CHUNK_WIDTH*World.TILE_WIDTH && e.getLocation().getX() > this.getLocation().getX()) { if (e.getLocation().getY() > this.getLocation().getY() && e.getLocation().getY() < this.getLocation().getY()+World.CHUNK_HEIGHT*World.TILE_HEIGHT) { return true; } } return false; What happens here is that it checks in a SQUARE around the chunk so not the real isometric bounds. Image example: (THE RED IS WHERE THE PROGRAM CHECKS THE BOUNDS) What I have now: Desired check: Ultimately I want to do the same for each tile in the chunk. EXTRA INFO: Till now what I had in my game is you could only move tile by tile but now I want them to move freely but I still need them to have a tile location so no matter where they are on the tile their tile location will be that certain tile. then when they are inside a different tile's bounding box then their tile location becomes the new tile. Same thing goes with chunks. the player does have an area but the area does not matter in this case. and as long as the X and Y are inside the bounding box then it should return true. they don't have to be completely on the tile.

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• How to remove seams from a tile map in 3D?

  - by Grimshaw

  I am using my OpenGL custom engine to render a tilemap made with Tiled, using a well spread tileset from the web. There is nothing fancy going on. I load the TMX file from Tiled and generate vertex arrays and index arrays to render the tilemap. I am rendering this tilemap as a wall in my 3D world, meaning that I move around with a fly camera in my 3D world and at Z=0 there is a plane showing me my tiles. Everything is working correctly but I get ugly seems between the tiles. I've tried orthographic and perspective cameras and with either I found particular sets of parameters for the projection and view matrices where the artifacts did not show, but otherwise they are there 99% of the time in multiple patterns, depending on the zoom and camera parameters like field of view. Here's a screenshot of the artifact being shown: http://i.imgur.com/HNV1g4M.png Here's the tileset I am using (which Tiled also uses and renders correctly): http://i.imgur.com/SjjHK4q.png My tileset has no mipmaps and is set to GL_NEAREST and GL_CLAMP_TO_EDGE values. I've looked around many articles in the internet and nothing helped. I tried uv correction so the uv fall at half of the texel, rather than the end of the texel to prevent interpolating with the neighbour value(which is transparency). I tried debugging with my geometry and I verified that with no texture and a random color in each tile, I don't seem to see any seams. All vertices have integer coordinates, i.e, the first tile is a quad from (0,0) to (1,1) and so on. Tried adding a little offset both to the UV and to the vertices to see if the gaps cease to exist. Disabled multisampling too. Nothing fixed it so far. Thanks.

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• From simple physics with a ball, to a more complicated shape

  - by Maximus

  Hello fellow game devs and stack overflowers... I recently made a transition from OpenGL ES 1.1 to 2.0 (on Android via NDK) and things are going well so far. I'm working on doing a dice rolling application (gaming dice up to 20 sided, not just regular 6 sided die) as a way to learn more about how physics is implemented in a gaming environment. I've explored implementing existing engine options (such as Bullet) and I don't think I need to implement something quite so sophisticated. I've found several tutorials that handle a lot of the general physics involved with initial trajectory, velocity, angle of contact and reflection angle, etc. I'm confident that I'd be able to implement ball-like behavior without much trouble. My question lies in when I attempt to make the interaction of the die shape with another surface more "realistic," for example... the die strikes the floor surface at such an angle where only one corner makes contact with the floor. In my mind, the center of gravity of the object would play a part in determining how the die bounces away, possibly even spinning it it faster, etc... but I am not sure what the actual math involved is. Are there any recommended resources for getting into this level of detail? Initial searches haven't turned up much... Thanks to everyone in the community, -Jeremiah

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• How can I unit test rendering output?

  - by stephelton

  I've been embracing Test-Driven Development (TDD) recently and it's had wonderful impacts on my development output and the resiliency of my codebase. I would like to extend this approach to some of the rendering work that I do in OpenGL, but I've been unable to find any good approaches to this. I'll start with a concrete example so we know what kinds of things I want to test; lets say I want to create a unit cube that rotates about some axis, and that I want to ensure that, for some number of frames, each frame is rendered correctly. How can I create an automated test case for this? Preferably, I'd even be able to write a test case before writing any code to render the cube (per usual TDD practices.) Among many other things, I'd want to make sure that the cube's size, location, and orientation are correct in each rendered frame. I may even want to make sure that the lighting equations in my shaders are correct in each frame. The only remotely useful approach to this that I've come across involves comparing rendered output to a reference output, which generally precludes TDD practice, and is very cumbersome. I could go on about other desired requirements, but I'm afraid the ones I've listed already are out of reach.

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• What is the correct and most efficient approach of streaming vertex data?

  - by Martijn Courteaux

  Usually, I do this in my current OpenGL ES project (for iOS): Initialization: Create two VBO's and one IndexBuffer (since I will use the same indices), same size. Create two VAO's and configure them, both bound to the same Index Buffer. Each frame: Choose a VBO/VAO couple. (Different from the previous frame, so I'm alternating.) Bind that VBO Upload new data using glBufferSubData(GL_ARRAY_BUFFER, ...). Bind the VAO Render my stuff using glDrawElements(GL_***, ...); Unbind the VAO However, someone told me to avoid uploading data (step 3) and render immediately the new data (step 5). I should avoid this, because the glDrawElements call will stall until the buffer is effectively uploaded to VRAM. So he suggested to draw all my geometry I uploaded the previous frame and upload in the current frame what will be drawn in the next frame. Thus, everything is rendered with the delay of one frame. Is this true or am I using the good approach to work with streaming vertex data? (I do know that the pipeline will stall the other way around. Ie: when you draw and immediately try to change the buffer data. But I'm not doing that, since I implemented double buffering.)

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• vector rotations for branches of a 3d tree

  - by freefallr

  I'm attempting to create a 3d tree procedurally. I'm hoping that someone can check my vector rotation maths, as I'm a bit confused. I'm using an l-system (a recursive algorithm for generating branches). The trunk of the tree is the root node. It's orientation is aligned to the y axis. In the next iteration of the tree (e.g. the first branches), I might create a branch that is oriented say by +10 degrees in the X axis and a similar amount in the Z axis, relative to the trunk. I know that I should keep a rotation matrix at each branch, so that it can be applied to child branches, along with any modifications to the child branch. My questions then: for the trunk, the rotation matrix - is that just the identity matrix * initial orientation vector ? for the first branch (and subsequent branches) - I'll "inherit" the rotation matrix of the parent branch, and apply x and z rotations to that also. e.g. using glm::normalize; using glm::rotateX; using glm::vec4; using glm::mat4; using glm::rotate; vec4 vYAxis = vec4(0.0f, 1.0f, 0.0f, 0.0f); vec4 vInitial = normalize( rotateX( vYAxis, 10.0f ) ); mat4 mRotation = mat4(1.0); // trunk rotation matrix = identity * initial orientation vector mRotation *= vInitial; // first branch = parent rotation matrix * this branches rotations mRotation *= rotate( 10.0f, 1.0f, 0.0f, 0.0f ); // x rotation mRotation *= rotate( 10.0f, 0.0f, 0.0f, 1.0f ); // z rotation Are my maths and approach correct, or am I completely wrong? Finally, I'm using the glm library with OpenGL / C++ for this. Is the order of x rotation and z rotation important?

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• Sprites, Primitives and logic entity as structs

  - by Jeffrey

  I'm wondering would it be considered acceptable: The window class is responsible for drawing data, so it will have a method: Window::draw(const Sprite&); Window::draw(const Rect&); Window::draw(const Triangle&); Window::draw(const Circle&); and all those primitives + sprites would be just public struct. For example Sprite: struct Sprite { float x, y; // center float origin_x, origin_y; float width, height; float rotation; float scaling; GLuint texture; Sprite(float w, float h); Sprite(float w, float h, float a, float b); void useTexture(std::string file); void setOrigin(float a, float b); void move(float a, float b); // relative move void moveTo(float a, float b); // absolute move void rotate(float a); // relative rotation void rotateTo(float a); // absolute rotation void rotationReset(); void scale(float a); // relative scaling void scaleTo(float a); // absolute scaling void scaleReset(); }; So instead of having each primitive to call their draw() function, which is a little bit off topic for their object, I let the Window class handle all the OpenGL stuff and manipulate them as simple objects that will be drawn later on. Is this pattern used? Does it have any cons against it's primitives-draw-themself pattern? Are there any other related patterns?

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• Rendering text with stb_font results in glitches

  - by Fabian Fritz

  I'm trying to render text with OpenGL and an "inline"-font taken from the stb_fonts The relevant code for initializing the font & rendering: LabelFactory::LabelFactory() { static unsigned char fontpixels [STB_SOMEFONT_BITMAP_HEIGHT][STB_SOMEFONT_BITMAP_WIDTH]; STB_SOMEFONT_CREATE(fontdata, fontpixels, STB_SOMEFONT_BITMAP_HEIGHT); glGenTextures(1, &texture); glBindTexture(GL_TEXTURE_2D, texture); glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE); glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, STB_SOMEFONT_BITMAP_WIDTH, STB_SOMEFONT_BITMAP_HEIGHT, 0, GL_ALPHA, GL_UNSIGNED_BYTE, fontdata); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); } void LabelFactory::renderLabel(Label * label) { int x = label->x; int y = label->y; const char * str = label->text; glBindTexture(GL_TEXTURE_2D, texture); glEnable(GL_BLEND); glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); glEnable(GL_ALPHA_TEST); glColor4f(1.0f, 1.0f, 1.0f, 1.0f); glEnable(GL_TEXTURE_2D); glBegin(GL_QUADS); while (*str) { int char_codepoint = *str++; stb_fontchar *cd = &fontdata[char_codepoint - STB_FONT_arial_14_usascii_FIRST_CHAR]; glTexCoord2f(cd->s0, cd->t0); glVertex2i(x + cd->x0, y + cd->y0); glTexCoord2f(cd->s1, cd->t0); glVertex2i(x + cd->x1, y + cd->y0); glTexCoord2f(cd->s1, cd->t1); glVertex2i(x + cd->x1, y + cd->y1); glTexCoord2f(cd->s0, cd->t1); glVertex2i(x + cd->x0, y + cd->y1); x += cd->advance_int; } glEnd(); } However this results in weird glitches I guess I'm doing something wrong with the alpha blending, however I was unable to improve it by changing the parameters. The size and length of the outline of the text that should be shown seems about right (it should read "Test Test Test").

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• Deferred Rendering With Diffuse,Specular, and Normal maps

  - by John

  I have been reading up on deferred rendering and I am trying to implement a renderer using the Sponza atrium model, which can be found here, as my sandbox.Note I am also using OpenGL 3.3 and GLSL. I am loading the model from a Wavefront OBJ file using Assimp. I extract all geometry information including tangents and bitangents. For all the aiMaterials,I extract the following information which essentially comes from the sponza.mtl file. Ambient/Diffuse/Specular/Emissive Reflectivity Coefficients(Ka,Kd,Ks,Ke) Shininess Diffuse Map Specular Map Normal Map I understand that I must render vertex attributes such as position ,normals,texture coordinates to textures as well as depth for the second render pass. A lot of resources mention putting colour information into a g-buffer in the initial render pass but do you not require the diffuse,specular and normal maps and therefore lights to determine the fragment colour? I know that doesnt make since sense because lighting should be done in the second render pass. In terms of normal mapping, do you essentially just pass the tangent,bitangents, and normals into g-buffers and then construct the tangent matrix and apply it to the sampled normal from the normal map. Ultimately, I would like to know how to incorporate this material information into my deferred renderer.

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• Quaternion LookAt for camera

  - by Homar

  I am using the following code to rotate entities to look at points. glm::vec3 forwardVector = glm::normalize(point - position); float dot = glm::dot(glm::vec3(0.0f, 0.0f, 1.0f), forwardVector); float rotationAngle = (float)acos(dot); glm::vec3 rotationAxis = glm::normalize(glm::cross(glm::vec3(0.0f, 0.0f, 1.0f), forwardVector)); rotation = glm::normalize(glm::quat(rotationAxis * rotationAngle)); This works fine for my usual entities. However, when I use this on my Camera entity, I get a black screen. If I flip the subtraction in the first line, so that I take the forward vector to be the direction from the point to my camera's position, then my camera works but naturally my entities rotate to look in the opposite direction of the point. I compute the transformation matrix for the camera and then take the inverse to be the View Matrix, which I pass to my OpenGL shaders: glm::mat4 viewMatrix = glm::inverse( cameraTransform->GetTransformationMatrix() ); The orthographic projection matrix is created using glm::ortho. What's going wrong?

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• GLSL Normals not transforming propertly

  - by instancedName

  I've been stuck on this problem for two days. I've read many articles about transforming normals, but I'm just totaly stuck. I understand choping off W component for "turning off" translation, and doing inverse/traspose transformation for non-uniform scaling problem, but my bug seems to be from a different source. So, I've imported a simple ball into OpenGL. Only transformation that I'm applying is rotation over time. But when my ball rotates, the illuminated part of the ball moves around just as it would if direction light direction was changing. I just can't figure out what is the problem. Can anyone help me with this? Here's the GLSL code: Vertex Shader: #version 440 core uniform mat4 World, View, Projection; layout(location = 0) in vec3 VertexPosition; layout(location = 1) in vec3 VertexColor; layout(location = 2) in vec3 VertexNormal; out vec4 Color; out vec3 Normal; void main() { Color = vec4(VertexColor, 1.0); vec4 n = World * vec4(VertexNormal, 0.0f); Normal = n.xyz; gl_Position = Projection * View * World * vec4(VertexPosition, 1.0); } Fragment Shader: #version 440 core uniform vec3 LightDirection = vec3(0.0, 0.0, -1.0); uniform vec3 LightColor = vec3(1f); in vec4 Color; in vec3 Normal; out vec4 FragColor; void main() { diffuse = max(0.0, dot(normalize(-LightDirection), normalize(Normal))); vec4 scatteredLight = vec4(LightColor * diffuse, 1.0f); FragColor = min(Color * scatteredLight, vec4(1.0)); }

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• How can I improve the "smoothness" of a 2D side-scrolling iPhone game?

  - by MrDatabase

  I'm working on a relatively simple 2D side-scrolling iPhone game. The controls are tilt-based. I use OpenGL ES 1.1 for the graphics. The game state is updated at a rate of 30 Hz... And the drawing is updated at a rate of 30 fps (via NSTimer). The smoothness of the drawing is ok... But not quite as smooth as a game like iFighter. What can I do to improve the smoothness of the game? Here are the potential issues I've briefly considered: I'm varying the opacity of up to 15 "small" (20x20 pixels) textures at a time... Apparently varying the opacity in this manner can degrade drawing performance I'm rendering at only 30 fps (via NSTimer)... Perhaps 2D games like iFighter are rendered at a higher frame rate? Perhaps the game state could be updated at a faster rate? Note the acceleration vales are updated at 100 Hz... So I could potentially update part of the game state at 100 hz All of my textures are PNG24... Perhaps PNG8 would help (due to smaller size etc)

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• Correcting Lighting in Stencil Reflections

  - by Reanimation

  I'm just playing around with OpenGL seeing how different methods of making shadows and reflections work. I've been following this tutorial which describes using GLUT_STENCIL's and MASK's to create a reasonable interpretation of a reflection. Following that and a bit of tweaking to get things to work, I've come up with the code below. Unfortunately, the lighting isn't correct when the reflection is created. glPushMatrix(); plane(); //draw plane that reflection appears on glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE); glDepthMask(GL_FALSE); glEnable(GL_STENCIL_TEST); glStencilFunc(GL_ALWAYS, 1, 0xFFFFFFFF); glStencilOp(GL_REPLACE, GL_REPLACE, GL_REPLACE); plane(); //draw plane that acts as clipping area for reflection glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE); glDepthMask(GL_TRUE); glStencilFunc(GL_EQUAL, 1, 0xFFFFFFFF); glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP); glDisable(GL_DEPTH_TEST); glPushMatrix(); glScalef(1.0f, -1.0f, 1.0f); glTranslatef(0,2,0); glRotatef(180,0,1,0); sphere(radius, spherePos); //draw object that you want to have a reflection glPopMatrix(); glEnable(GL_DEPTH_TEST); glDisable(GL_STENCIL_TEST); sphere(radius, spherePos); //draw object that creates reflection glPopMatrix(); It looked really cool to start with, then I noticed that the light in the reflection isn't correct. I'm not sure that it's even a simple fix because effectively the reflection is also a sphere but I thought I'd ask here none-the-less. I've tried various rotations (seen above the first time the sphere is drawn) but it doesn't seem to work. I figure it needs to rotate around the Y and Z axis but that's not correct. Have I implemented the rotation wrong or is there a way to correct the lighting?

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• Heightmap and Textures

  - by Robert

  Im trying to find the "best way" to apply a texture to a heightmap with opengl 3.x. Its really hard to find something on google because tutorials are olds and they're all using different methods, im really lost and i dont know what to use at all. Here is my code that generates the heightmap (its basic) float[] vertexes = null; float[] textureCoords = null; for(int x = 0; x < this.m_size.width; x++) { for(int y = 0; y < this.m_size.height; y++) { vertexes ~= [x, 1.0f, y]; textureCoords ~= [cast(float)x / 50, cast(float)y / 50]; } } As you can see, i dont know how to apply the texture at all (i was using / 50 for my tests). Result of that code : I would like to have something very basic like : (you can find more pics in his blog) Edit : my texture size is 1024x1024.

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• My game seems to be incompatible with recording software. What could be causing this?

  - by Lewis Wakeford

  I've just finished a little Game-Dev project for university and I need to record a video to accompany my submission (just in case they can't get my source to work). Basically my game doesn't work at all when FRAPS or Bandicam attempts to attach to it, I get a black screen and a stream of GL INVALID OPERATION messages from my error reporting code. Dxtory can't seem to hook into it correctly at all, it doesn't display it's FPS counter or anything. My game logic appears to be running correctly from the debug traces, it just seems like all the gl library calls break. I don't know a huge amount about how these programs operate so I don't really know what I could be doing to cause this. I've heard they read from the OpenGL frame buffers so maybe I'm doing something wrong there? I'm letting GLFW and GLEW do all the low level initialization, but I have successfully recorded projects with the same setup and recording software. Essentially, has anyone ever run into something like this before or do you know anything about how these programs work that could give a clue as to the cause of the issue?

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• How do I draw a scrolling background?

  - by droidmachine

  How can I draw background tile in my 2D side-scrolling game? Is that loop logical for OpenGL es? My tile 2400x480. Also I want to use parallax scrolling for my game. batcher.beginBatch(Assets.background); for(int i=0; i<100; i++) batcher.drawSprite(0+2400*i, 240, 2400, 480, Assets.backgroundRegion); batcher.endBatch(); UPDATE And thats my onDrawFrame.I'm sending deltaTime for fps control. public void onDrawFrame(GL10 gl) { GLGameState state = null; synchronized(stateChanged) { state = this.state; } if(state == GLGameState.Running) { float deltaTime = (System.nanoTime()-startTime) / 1000000000.0f; startTime = System.nanoTime(); screen.update(deltaTime); screen.present(deltaTime); } if(state == GLGameState.Paused) { screen.pause(); synchronized(stateChanged) { this.state = GLGameState.Idle; stateChanged.notifyAll(); } } if(state == GLGameState.Finished) { screen.pause(); screen.dispose(); synchronized(stateChanged) { this.state = GLGameState.Idle; stateChanged.notifyAll(); } } }

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• Trouble with Collada bones

  - by KyleT

  I have a Collada file with a rigged mesh. I've read the node tags in the library_visual_scenes tag and extracted the matrix for each node and stored everything in a hierarchical bone structure. My Matrix container is "row major", so I'd store the first float of a matrix tag in the 1st row, 1st column, the second in the 1st row, 2nd column, etc. From what I gather this is the Bind Pose Matrix. After that I went through the tag and extracted the float array in the source tag of the skin tag of the controller for the mesh. I stored each matrix from this float array in their corresponding Bone as the Inverse Bind Matrix. I also extracted the bind-shape-matrix and stored it. Now I'd like to draw the skeleton with OpenGL to see if everything is working correctly before I go about skinning. I iterate once over my bones and multiply a bone's Bind Pose Matrix by it's parents and store that. After that I iterate again over the bones and multiply the result of the previous matrix multiplication by the Inverse Bind Matrix and then by the Bind Shape Matrix. The results look something like this: [0.2, 9.2, 5.8, 1.2 ] [4.6, -3.3, -0.2, -0.1 ] [-1.8, 0.2, -4.2, -3.9 ] [0, 0, 0, 1 ] I've had to go to various sources to get the little understanding of Collada I have and books about 3d transform matricies can get pretty intense. I've hit a brick wall and if you could please read through this and see if there is something I'm doing wrong, and how I'd go about getting an X,Y,Z to draw a point for each of these joints once I've calculated the final transform, I'd really appreciate it.

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• pointers to member functions in an event dispatcher

  - by derivative

  For the past few days I've been trying to come up with a robust event handling system for the game (using a component based entity system, C++, OpenGL) I've been toying with. class EventDispatcher { typedef void (*CallbackFunction)(Event* event); typedef std::unordered_map<TypeInfo, std::list<CallbackFunction>, hash_TypeInfo > TypeCallbacksMap; EventQueue* global_queue_; TypeCallbacksMap callbacks_; ... } global_queue_ is a pointer to a wrapper EventQueue of std::queue<Event*> where Event is a pure virtual class. For every type of event I want to handle, I create a new derived class of Event, e.g. SetPositionEvent. TypeInfo is a wrapper on type_info. When I initialize my data, I bind functions to events in an unordered_map using TypeInfo(typeid(Event)) as the key that corresponds to a std::list of function pointers. When an event is dispatched, I iterate over the list calling the functions on that event. Those functions then static_cast the event pointer to the actual event type, so the event dispatcher needs to know very little. The actual functions that are being bound are functions for my component managers. For instance, SetPositionEvent would be handled by void PositionManager::HandleSetPositionEvent(Event* event) { SetPositionEvent* s_p_event = static_cast<SetPositionEvent*>(event); ... } The problem I'm running into is that to store a pointer to this function, it has to be static (or so everything leads me to believe.) In a perfect world, I want to store pointers member functions of a component manager that is defined in a script or whatever. It looks like I can store the instance of the component manager as well, but the typedef for this function is no longer simple and I can't find an example of how to do it. Is there a way to store a pointer to a member function of a class (along with a class instance, or, I guess a pointer to a class instance)? Is there an easier way to address this problem?

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• Can anyone point me to some open source directX rendering engines or frameworks? [on hold]

  - by Jim

  I'm completely new to graphics API programmming, but not at all new to the theory and principle operation of game engines and rendering engines. That being said, I want to do some experiments of rendering very dense geometry scenes in a basic rendering engine or game engine. I don't need a lot of bells and whistles. What I need is enough control that I can implement my own scene graph algorithms and control the rendering pipeline very specifically. My ideal candidate engine would be either a rendering engine or game engine with a modular design that might be ready to go out of the box but would be simple enough in case I need to rip out some of the guts in the rendering management and implement my own. It's a tough call because I'm right at the level where it's almost better to go from scratch, but there's no sense in having to build every single basic thing such as heirarchical transforms, etc. I just want to work with rendering optimization to push dense geometry for maximum FPS. Does anyone have a suggestion for an engine or basic framework to use? I requested DirectX in my title because I figured it would likely be better supported and less likely for me to run into some obscure less-documented problem. But OpenGL might be acceptable if the recommended framework was definitely better than my other options. EDIT: I should add that I really want GPU tessellation support (part of adding to the density of geometry detail).

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• Matrix loading problems with jbullet and lwjgl

  - by Quintin

  The following code does not load the matrix correctly from jbullet. //box is a RigidBody Transform trans = new Transform(); trans = box.getMotionState().getWorldTransform(trans); float[] matrix = new float[16]; trans.getOpenGLMatrix(matrix); // pass that matrix to OpenGL and render the cube FloatBuffer buffer = ByteBuffer.allocateDirect(4*16).asFloatBuffer().put(matrix); buffer.rewind(); glPushMatrix(); glMultMatrix(buffer); glBegin(GL_POINTS); glVertex3f(0,0,0); glEnd(); glPopMatrix(); the jbullet is configured as so: CollisionConfiguration = new DefaultCollisionConfiguration(); dispatcher = new CollisionDispatcher(collisionConfiguration); Vector3f worldAabbMin = new Vector3f(-10000,-10000,-10000); Vector3f worldAabbMax = new Vector3f(10000,10000,10000); AxisSweep3 overlappingPairCache = new AxisSweep3(worldAabbMin, worldAabbMax); SequentialImpulseConstraintSolver solver = new SequentialImpulseConstraintSolver(); dynamicWorld = new DiscreteDynamicsWorld(dispatcher, overlappingPairCache, solver, collisionConfiguration); dynamicWorld.setGravity(new Vector3f(0,-10,0)); dynamicWorld.getDispatchInfo().allowedCcdPenetration = 0f; CollisionShape groundShape = new BoxShape(new Vector3f(1000.f, 50.f, 1000.f)); Transform groundTransform = new Transform(); groundTransform.setIdentity(); groundTransform.origin.set(new Vector3f(0.f, -60.f, 0.f)); float mass = 0f; Vector3f localInertia = new Vector3f(0, 0, 0); DefaultMotionState myMotionState = new DefaultMotionState(groundTransform); RigidBodyConstructionInfo rbInfo = new RigidBodyConstructionInfo(mass, myMotionState, groundShape, localInertia); RigidBody body = new RigidBody(rbInfo); dynamicWorld.addRigidBody(body); dynamicWorld.clearForces(); Nothing is rendered on the screen. What am I doing wrong?

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• Issues implementing arcball viewer

  - by Pris

  My scene has a simple cube, and a camera built with the lookAt function (I'm using OpenGL). The scene renders fine, and I'm sure I have my model/view/projection matrices set up correctly. Now I'm trying to implement arcball rotation for my camera, but I'm having some trouble. I've got it down to calculating the angle/axis rotation for a virtual sphere in normalized screen coordinates. That means when I move my mouse left to right, I get an angle around the Y axis... and moving my mouse up/down will get me an angle about X. I'm not sure where to go from here -- what do I need to do with my axis so I can apply the angle to simulate camera rotation about its viewpoint? If I try directly applying the axis/angle rotation the camera/view transform I get what you'd expect. The view is rotated about the world axes which the mouse moving over the virtual sphere on the screen corresponds to. So if I move the mouse up/down the view rotates about the world's X axis (what I get reminds me of a first-person view)... but this isn't what I want. I think I need the axis I get to be transformed so it passes through the camera viewpoint and is oriented correct in reference to the camera... but I don't know if that's right or how to do that.

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• Fourth texture = segmentation fault

  - by Robin92

  I keep on getting segmentation fault each time I load fourth texture - what type of texture, I mean filename, does not matter. I checked value of GL_TEXTURES_STACK_SIZE which turned out to be 10 so quite more than 4, isn't it? Here're code fragments: funciton to load texture from png static GLuint gl_loadTexture(const char filename[]) { static int iTexNum = 1; GLuint texture = 0; img_s *img = NULL; img = img_loadPNG(filename); if (img) { glGenTextures(iTexNum++, &texture); glBindTexture(GL_TEXTURE_2D, texture); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR); glTexImage2D(GL_TEXTURE_2D, 0, img->iGlFormat, img->uiWidth, img->uiHeight, 0, img->iGlFormat, GL_UNSIGNED_BYTE, img->p_ubaData); img_free(img); //it may cause errors on windows } else printf("Error: loading texture '%s' failed!\n", filename); return texture; } actual loading static GLuint textures[4]; static void gl_init() { (...) //setting up OpenGL /* loading textures */ textures[0] = gl_loadTexture("images/background.png"); textures[1] = gl_loadTexture("images/spaceship.png"); textures[2] = gl_loadTexture("images/asteroid.png"); textures[3] = gl_loadTexture("images/asteroid2.png"); //this is causing SegFault no matter which file I load! } Any ideas? Problem is present on both Linux and Windows.

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• Sprite batching seems slow

  - by Dekowta

  I have implemented a sprite batching system in OpenGL which will batch sprites based on their texture. How ever when I'm rendering ~5000 sprites all using the same texture i'm getting roughly 30fps. The process is as followed create sprite batch which also create a VBO with a set size and also creates the shaders as well call begin and initialise the render mode (at the moment just setting alpha on) call Draw with a sprite. This checks to see if the texture of the sprite has already been loaded and if so it just creates a pointer to the batch item and adds the new sprite coords. If not then it creates a new batch item and adds the sprite coords to that; it adds the batch item to the main batch. if the max sprite count is reached render will be called call end which calls render to render the left over sprites in the batch. and also resets the buffer offset render loops through each item in the batch and will bind the texture of the batch item, map the data to the buffer and then draw the array. the buffer will then be offset by the amount of sprites drawn. I have a feeling that it could be the method i'm using to store the batched sprites or it could be something else that i'm missing but I still can work it out. the cpp and h files are as followed http://pastebin.com/ZAytErGB http://pastebin.com/iCB608tA On top of this i'm also getting a weird issue where then two sprites are batched on after the other the second sprite will use the same coordinates as the last. And then when one if drawn after it is fine. I can't seem to find what is causing this issue. any help would be appreciated iv been sat trying to work this all out for a while now and cant seems to put my finger on what's causing it all.

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• Why is my Python OpenGL render2DTexture function so slow?

  - by Barakat

  SOLVED: The problem was actually using time.time() every CPU cycle to see whether the next frame should be drawn or not. The time it takes to execute time.time() was having an impact on the FPS. I made this function for drawing 2D textures as images in a 2D view in my OpenGL application. After doing some testing I found that it takes up 1-2 fps per texture. I know I am probably doing something wrong in this code. Any ideas? I am limiting the FPS to 60. Edit: When I disable the texture rendering it adds about 15% fps back. When I disabled text rendering it adds about 15% fps back. When i disable both barely any fps is consumed anymore. IE: 20 out of 60 fps with both on. 30 out of 60 when one is disabled. 58 out of 60 when both are disabled. When rendering the text on a button ( the control I'm using to test this ), it only "prepares" the text when the button label is set. Updated code, still running at the same speed but still works the same: def render2DTexture( self, texture, rect, texrect ): glEnable( GL_TEXTURE_2D ) glBindTexture( GL_TEXTURE_2D, texture ) glBegin( GL_QUADS ) glTexCoord2f( texrect.left, texrect.bottom ) glVertex2i( rect.left, self.windowSize[1] - rect.top ) glTexCoord2f( texrect.right, texrect.bottom ) glVertex2i( rect.left + rect.right, self.windowSize[1] - rect.top ) glTexCoord2f( texrect.right, texrect.top ) glVertex2i( rect.left + rect.right, self.windowSize[1] - ( rect.top + rect.bottom ) ) glTexCoord2f( texrect.left, texrect.top ) glVertex2i( rect.left, self.windowSize[1] - ( rect.top + rect.bottom ) ) glEnd() glDisable( GL_TEXTURE_2D ) def prepareText( self, text, fontFace, color ): self.loadFont( fontFace ) bmp = self.fonts[ fontFace ].render( text, 1, color ) return ( pygame.image.tostring( bmp, 'RGBA', 1 ), bmp.get_width(), bmp.get_height() ) def renderText( self, pText, position ): glRasterPos2i( position[0], self.windowSize[1] - ( position[1] + pText[2] ) ) glDrawPixels( pText[1], pText[2], GL_RGBA, GL_UNSIGNED_BYTE, pText[0] )

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