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• Rotate a particle system

  - by Blueski

  Languages / Libraries in use: C++, OpenGL, GLUT Okay, here's the deal. I've got a particle system which shoots out alpha blended textures to produce a flame. The system only keeps track of very basic things such as, time alive, life, xyz and spread. The direction in which the flames are currently moving in is purely based on other things which are going on in my code ( I assume ). My goal however, is to attach the flame to the camera (DONE) and have the flame pointing in the direction my camera is facing (NOT WORKING). I've tried glRotate for both x,y,z and I can't get it to work properly. I'm currently using gluLookAt to move the camera, and get the flame to follow the XYZ of the camera by calling glTranslatef(camX, camY - offset, camZ); Any suggestions on how I can rotate the direction of the flame with the camera would be greatly appreciated. Heres an image of what I've got: http://i.imgur.com/YhV4w.png Notes: Crosshair depicts where camera is facing if I turn the camera, flame doesn't follow the crosshair Also asked here: http://stackoverflow.com/questions/9560396/rotate-a-particle-system but was referred here

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• File format for animated scene

  - by stephelton

  I've got a custom OpenGL based rendering engine and I'd like to add support for cinema-type scene animation. The artist that is helping me uses primarily 3DSMax. I'd like a file format for exporting and importing this data. I'm also in need of a file format for skeletal animation data, which may have an impact here. I've been looking at MAXScript to manually export this stuff, which would buy me the most flexibility, but I have virtually no experience with 3DSMax itself, so I get a little lost when it comes to terminology. So I'd like to know what file formats exist for animated scene data, and whether they are appropriate for my use (my fear is that they will be way too broad for my fairly simple needs.) The way I view animated scene data is basically a bunch of references to [animated] models with keyframe-based matrices describing their orientation over time. And probably some special camera stuff to handle perspective. I might also want some event type stuff for adding/removing objects. Is this a sane concept?

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• How to create per-vertex normals when reusing vertex data?

  - by Chris Smith

  I am displaying a cube using a vertex buffer object (gl.ELEMENT_ARRAY_BUFFER). This allows me to specify vertex indicies, rather than having duplicate vertexes. In the case of displaying a simple cube, this means I only need to have eight vertices total. Opposed to needing three vertices per triangle, times two triangles per face, times six faces. Sound correct so far? My question is, how do I now deal with vertex attribute data such as color, texture coordinates, and normals when reusing vertices using the vertex buffer object? If I am reusing the same vertex data in my indexed vertex buffer, how can I differentiate when vertex X is used as part of the cube's front face versus the cube's left face? In both cases I would like the surface normal and texture coordinates to be different. I understand I could average the surface normal, however I would like to render a cube. Also, this still doesn't work for texture coordinates. Is there a way to save memory using a vertex buffer object while being able to provide different vertex attribute data based on context? (Per-triangle would be idea.) Or should I just duplicate each vertex for each context in which it gets rendered. (So there is a one-to-one mapping between vertex, normal, color, etc.) Note: I'm using OpenGL ES.

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• FreeType2 Crash on FT_Init_FreeType

  - by JoeyDewd

  I'm currently trying to learn how to use the FreeType2 library for drawing fonts with OpenGL. However, when I start the program it immediately crashes with the following error: "(Can't correctly start the application (0xc000007b))" Commenting the FT_Init_FreeType removes the error and my game starts just fine. I'm wondering if it's my code or has something to do with loading the dll file. My code: #include "SpaceGame.h" #include <ft2build.h> #include FT_FREETYPE_H //Freetype test FT_Library library; Game::Game(int Width, int Height) { //Freetype FT_Error error = FT_Init_FreeType(&library); if(error) { cout << "Error occured during FT initialisation" << endl; } And my current use of the FreeType2 files. Inside my bin folder (where debug .exe is located) is: freetype6.dll, libfreetype.dll.a, libfreetype-6.dll. In Code::Blocks, I've linked to the lib and include folder of the FreeType 2.3.5.1 version. And included a compiler flag: -lfreetype My program starts perfectly fine if I comment out the FT_Init function which means the includes, and library files should be fine. I can't find a solution to my problem and google isn't helping me so any help would be greatly appreciated.

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• Blur gets displaced compared to original image

  - by user1294203

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

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• How to implement physical effect, perspective effect on Android

  - by asedra_le

  I'm researching about 2D game for Android to implement an Android Game Project. My project looks nearly like PaperToss. Instance of throwing a page, my game will throw a coin. Suppose that I have a coin put in three-dimensional that have coordinates at A(x,y,z). I throw that point ahead, after 1/100 second, that coin move from A(x,y,z) to A'(x',y',z'). By this way, I have two problems need to solve. Determine the formulas can be used to compute the coordinates of the coin at time t. This problem is under-researching. I have no idea to solve this problem. Mapping three-dimensional points to a two-dimensional and use those new coordinates (a two-dimensional coordinates) to draw our coin on screen. I have found two solutions for this problem: Orthographic projection & Perspective projection However, my old friend said that OpenGL supports to solve problems like my problems. Any body have experiences about my problems? Help me please :) Thank for reading my question.

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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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• Z-order with Alpha blending in a 3D world

  - by user41765

  I'm working on a game in a 3D world with 2D sprites only (like Don't Starve game). (OpenGL ES2 with C++) Currently, I'm ordering elements back to front before drawing them without batch (so 1 element = 1 drawcall). I would like to implement batching in my framework to decrease draw calls. Here is what I've got for the moment: Order all elements of my scene back to front. Send order list of elements to the Renderer. Renderer look in his batch manager if a batch exist for the given element with his Material. Batch didn't exist: create a new one. Batch exist for element with this Material: Add sprite to the batch. Compute big mesh with all sprite for each batch (1 material type = 1 batch). When all batches are ok, the batch manager compute draw commands for the renderer. Renderer process draw commands (bind shader, bind textures, bind buffers, draw element) Image with my problem here: Explication here But I've got some problems because objects can be behind another objects inside another batch. How can I do something like that? Thanks!

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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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• GLES2.0 3D Android game performance and multi threading the update?

  - by Ofer

  I have profiled my mixed Java\C++ Android game and I got the following result: https://dl.dropbox.com/u/8025882/PompiDev/AndroidProfile.png As you can see, the pink think is a C++ functions that updates the game. It does things like updating the logic but it mostly it generates a "request list" for rendering. The thing is, I generate DrawLists on C++ and then send them to Java to process and draw using GLES2.0. Since then I was able to improve update from 9ms down to about 7ms, but I would like to ask if I would benefit from multi threading the update? As I understand from that diagram is that the function that takes the most time is the one you see it's color on the timeline. So the pink area is taken mostly by update. The other area has MainOpenGL.Handle as it's main contributor(whch is my java function), but since it's not drawn to the top of the diagram I can conclude other things are happening at the same time that use the CPU? Or even GPU stuff that isn't shown in this diagram. I am not sure how the GPU works on this. Does it calculate stuff in parallel to the CPU? Or is it part of the CPU usage as in SoC? I am not sure. Anyway, in case GPU things DO happen in parallel to CPU, then I would guess that if I do this C++ Update in parallel to the thread that makes the OpenGL calls, I might make use of "dead CPU time" due to GPU stalling or maybe have the GPU calls getting processed earlier because it won't have to wait for Update to finish? How do you suggest to improve performance based on that? Thanks.

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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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