Sign in to follow this  
snobaste

OpenGL OpenGL Fog on integrated graphics

Recommended Posts

Hello, first time poster here :)

I have been working on an OpenGL game and have recently sent copies to friends to test out.

On my machine and any of the ones I've tested it on (all with dedicated graphics cards ranging from an old Radeon X1600 Mobility to an nVidia GeForce GTX 580), my OpenGL fog displays correctly:
[media]http://img8.imageshack.us/img8/4047/sorrowsong2011071221410.png[/media]

However, when others run the game (specifically on laptops with Intel GMA onboard graphics), the fog does not render correctly:
[media]http://img37.imageshack.us/img37/1614/sorrowsong2011071221410.jpg[/media]

Here's how I'm initializing my OpenGL context:
[source]
glewInit();

glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

glDisable(GL_DEPTH_TEST);

glViewport(0, 0, screenWidth, screenHeight);
glDisable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE);
glEnable(GL_TEXTURE_2D);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, screenWidth, screenHeight, 0, 0.1f, 1000.0f);
if(accumBufferSupport) {
glClearAccum(0.0, 0.0, 0.0, 1.0);
glClear(GL_ACCUM_BUFFER_BIT);
}

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glEnable(GL_FOG);
glFogi(GL_FOG_MODE, GL_LINEAR);

glFogf(GL_FOG_DENSITY, 0.55f);
glFogf(GL_FOG_START, 1000.0f);
glFogf(GL_FOG_END, 1500.0f);
GLfloat fogColor[4]= {1.0f, 1.0f, 1.0f, 1.0f};
glFogfv(GL_FOG_COLOR, fogColor);

glHint(GL_FOG_HINT, GL_NICEST);

glEnable(GL_CULL_FACE);
[/source]

Then, when each level of the game is loaded, the fog color is changed with glFogfv(GL_FOG_COLOR, fogColor) and nothing else.

Also, because the game is 2D with 3D backgrounds, I switch projection modes each frame:
[source]
// Use perspective
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45, 4.0f/3.0f, 0.1f, 100000.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

glPushAttrib(GL_VIEWPORT_BIT);
glViewport(...); // Viewport math left out for length... this just sets the viewport to the game rectangle on screen

// Code to render background here

// Go back to orthographic
glPopAttrib();
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, screenWidth, screenHeight, 0, 0.1f, 1000.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
[/source]

I'm guessing the problem might have something to do with the Z-ordering, but I'm not understanding why it's happening only on integrated cards. It also doesn't appear to be a problem with older versions of OpenGL, either. The fog runs fine on the Radeon X1600 (OpenGL 2.0), but then doesn't run on the Intel GMA X4500 HD (OpenGL 2.1).

I haven't been able to find anything online about this issue and was wondering if anyone knows what the problem might be.

Thanks :)

Share this post


Link to post
Share on other sites
Is the background plane rendered as a single quad with fog, or do you have many passes or more complex geometry?

It's possible that it's just a driver problem, but you could try logging some pixel format information and see so you don't get a 16-bit z-buffer, if you believe that could cause the artifact. You should be able to force a 16-bit z buffer when selecting the pixel format, to try it out on your own system.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Forum Statistics

    • Total Topics
      627712
    • Total Posts
      2978765
  • Similar Content

    • By DelicateTreeFrog
      Hello! As an exercise for delving into modern OpenGL, I'm creating a simple .obj renderer. I want to support things like varying degrees of specularity, geometry opacity, things like that, on a per-material basis. Different materials can also have different textures. Basic .obj necessities. I've done this in old school OpenGL, but modern OpenGL has its own thing going on, and I'd like to conform as closely to the standards as possible so as to keep the program running correctly, and I'm hoping to avoid picking up bad habits this early on.
      Reading around on the OpenGL Wiki, one tip in particular really stands out to me on this page:
      For something like a renderer for .obj files, this sort of thing seems almost ideal, but according to the wiki, it's a bad idea. Interesting to note!
      So, here's what the plan is so far as far as loading goes:
      Set up a type for materials so that materials can be created and destroyed. They will contain things like diffuse color, diffuse texture, geometry opacity, and so on, for each material in the .mtl file. Since .obj files are conveniently split up by material, I can load different groups of vertices/normals/UVs and triangles into different blocks of data for different models. When it comes to the rendering, I get a bit lost. I can either:
      Between drawing triangle groups, call glUseProgram to use a different shader for that particular geometry (so a unique shader just for the material that is shared by this triangle group). or
      Between drawing triangle groups, call glUniform a few times to adjust different parameters within the "master shader", such as specularity, diffuse color, and geometry opacity. In both cases, I still have to call glBindTexture between drawing triangle groups in order to bind the diffuse texture used by the material, so there doesn't seem to be a way around having the CPU do *something* during the rendering process instead of letting the GPU do everything all at once.
      The second option here seems less cluttered, however. There are less shaders to keep up with while one "master shader" handles it all. I don't have to duplicate any code or compile multiple shaders. Arguably, I could always have the shader program for each material be embedded in the material itself, and be auto-generated upon loading the material from the .mtl file. But this still leads to constantly calling glUseProgram, much more than is probably necessary in order to properly render the .obj. There seem to be a number of differing opinions on if it's okay to use hundreds of shaders or if it's best to just use tens of shaders.
      So, ultimately, what is the "right" way to do this? Does using a "master shader" (or a few variants of one) bog down the system compared to using hundreds of shader programs each dedicated to their own corresponding materials? Keeping in mind that the "master shaders" would have to track these additional uniforms and potentially have numerous branches of ifs, it may be possible that the ifs will lead to additional and unnecessary processing. But would that more expensive than constantly calling glUseProgram to switch shaders, or storing the shaders to begin with?
      With all these angles to consider, it's difficult to come to a conclusion. Both possible methods work, and both seem rather convenient for their own reasons, but which is the most performant? Please help this beginner/dummy understand. Thank you!
    • By JJCDeveloper
      I want to make professional java 3d game with server program and database,packet handling for multiplayer and client-server communicating,maps rendering,models,and stuffs Which aspect of java can I learn and where can I learn java Lwjgl OpenGL rendering Like minecraft and world of tanks
    • By AyeRonTarpas
      A friend of mine and I are making a 2D game engine as a learning experience and to hopefully build upon the experience in the long run.

      -What I'm using:
          C++;. Since im learning this language while in college and its one of the popular language to make games with why not.     Visual Studios; Im using a windows so yea.     SDL or GLFW; was thinking about SDL since i do some research on it where it is catching my interest but i hear SDL is a huge package compared to GLFW, so i may do GLFW to start with as learning since i may get overwhelmed with SDL.  
      -Questions
      Knowing what we want in the engine what should our main focus be in terms of learning. File managements, with headers, functions ect. How can i properly manage files with out confusing myself and my friend when sharing code. Alternative to Visual studios: My friend has a mac and cant properly use Vis studios, is there another alternative to it?  
    • By ferreiradaselva
      Both functions are available since 3.0, and I'm currently using `glMapBuffer()`, which works fine.
      But, I was wondering if anyone has experienced advantage in using `glMapBufferRange()`, which allows to specify the range of the mapped buffer. Could this be only a safety measure or does it improve performance?
      Note: I'm not asking about glBufferSubData()/glBufferData. Those two are irrelevant in this case.
    • By xhcao
      Before using void glBindImageTexture(    GLuint unit, GLuint texture, GLint level, GLboolean layered, GLint layer, GLenum access, GLenum format), does need to make sure that texture is completeness. 
  • Popular Now