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Type: Posts; User: mbentrup

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    Generally you cannot request an OpenGL context of...

    Generally you cannot request an OpenGL context of a specific version. The GLW API, which is the link between OpenGL and the Windows system allows the application to specify an OpenGL version, but it...
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    If you have samples per Pixel, the OpenGL may...

    If you have <n> samples per Pixel, the OpenGL may run the fragment shader any number between 1 and <n> times per fragment. If the number of fragment shader invocations is less than the number of...
  3. Another issue may be that you have automatic...

    Another issue may be that you have automatic mipmap generation enabled, that would require decompress/downscale/recompress to next lower level steps for the compressed format, while uncompressed...
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    You should set stencil to 1 instead of increment...

    You should set stencil to 1 instead of increment in step 1.1.3, otherwise it would fail if the shape overlaps itself.
  5. Clipping a triangle by a sphere will not give you...

    Clipping a triangle by a sphere will not give you another triangle (or two) as clipping it with a plane does. You could instead use a fragment shader to discard all fragments outside the clipping...
  6. When you request version 3.0 you will get a...

    When you request version 3.0 you will get a compatibility context (well, technichally there are no profiles before version 3.2, but the contexts <= 3.1 behave exactly like compatibilty contexts),...
  7. The texture proxy will *not* tell you if there's...

    The texture proxy will *not* tell you if there's enough memory to allocate a texture of that size, it checks only that the driver is generally capable of working with a texture of the given size and...
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    The post-VS cache in modern GPUs is not a strict...

    The post-VS cache in modern GPUs is not a strict FIFO, because the vertices are processed in parallel. I think AMD GPUs process up to 64 vertices at the same time and NVidia 32. However, the FIFO...
  9. Look here:...

    Look here: http://www.opengl.org/sdk/docs/manglsl/xhtml/textureSize.xml
  10. This is addressed in issue #10 of...

    This is addressed in issue #10 of http://www.opengl.org/registry/specs/ARB/texture_view.txt. You have to be careful because a compressed texture and a matching integer texture will have different...
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    The difference is that you draw all the QUADS in...

    The difference is that you draw all the QUADS in one batch (one glBegin/glEnd pair), while the VBO version makes a draw call for every two triangles. Try to make one index buffer containing 20000...
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    The shader objects are needed only for linking...

    The shader objects are needed only for linking the program, you can delete them after you linked the program.
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    Unless you have a driver supporting...

    Unless you have a driver supporting GL_ARB_shader_stencil_export there's no easy way to do that. When I needed a certain pattern in the stencil buffer for stencil routing I ended up with an 8-pass...
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    The funny thing is that the GLX protocol for...

    The funny thing is that the GLX protocol for buffer objects is fully defined by the ARB, including the MapBuffer and MapBufferRange calls, in the respective ARB extension docs. What is missing are...
  15. This "polygon buffer" method works great when you...

    This "polygon buffer" method works great when you draw polygons sequentially, anything deserving the attribute "fast" on a GPU has to work parallelized.
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    Well, indirect GLX allows the sharing of buffer...

    Well, indirect GLX allows the sharing of buffer objects between different clients, so "the" client byte order may be ambigous. The way GLX handles this is that it doesn't allow the creation of any GL...
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    GL_LINEAR_MIPMAP_NEAREST is not a valid...

    GL_LINEAR_MIPMAP_NEAREST is not a valid magnification filter, it is only allowed for minification. You should use GL_LINEAR there.
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    Even if VBOs are technically faster than...

    Even if VBOs are technically faster than immediate mode, you may not see an improvement if the bottleneck of your application is somewhere else. The GPU works like a pipeline and the slowest stage...
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    Don't forget that there's extension for sparse...

    Don't forget that there's extension for sparse textures which may be impractical to transfer as a whole. The bind to FBO/ReadPixels workaround may also fail, because FBOs usually aren't capable to...
  20. glGetString(GL_EXTENSIONS) is usually only NULL...

    glGetString(GL_EXTENSIONS) is usually only NULL when you have no current OpenGL context. Also WGL_EXT_swap_control is not a GL extension, but a WGL extension, so you should use...
  21. How would your strongly typed Pascal binding deal...

    How would your strongly typed Pascal binding deal with glDrawBuffer(), which accepts GL_FRONT, GL_BACK, GL_FRONT_AND_BACK, but also GL_NONE, GL_FRONT_LEFT, GL_FRONT_RIGHT, etc. ?
  22. You pass the address of a stack-allocated...

    You pass the address of a stack-allocated structure to pthread_create, this will be destroyed as soon as the main thread leaves init(), so probably before the loader thread has a chance to read the...
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    Nvidia called this "pseudo instancing", and...

    Nvidia called this "pseudo instancing", and showed some significant performance gains on old GPUs by using vertex attributes. Performance on DX10+ GPUs may be different.
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    AMD does it that way on the southern island chips...

    AMD does it that way on the southern island chips according to their open ISA documents:



    The GPU has some dedicated interpolation instructions for the fragment shader.
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    This will make all varyings behave as if they...

    This will make all varyings behave as if they were declared "noperspective".

    Also note that after viewport transformation the vertex coordinates are usually converted to fixed-point numbers with...
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