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Type: Posts; User: Cornix

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  1. If I had to guess I would say the problem is with...

    If I had to guess I would say the problem is with depth testing. Even if a face is translucent it may write a value to the depth buffer. A face that is later drawn may then be discarded because it...
  2. They are slow because the data has to travel from...

    They are slow because the data has to travel from your program to OpenGL. Every OpenGL function call is expensive, especially if data has to be moved around from main memory (or CPU cache) to video...
  3. You have to remember that it does not matter how...

    You have to remember that it does not matter how you upload your data, it is still the same amount of data. For example, if you use immediate mode to draw your sprites, you are still uploading all...
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    With glScissor you can specify a rectangular area...

    With glScissor you can specify a rectangular area and with glEnable(GL_SCISSOR_TEST) you can activate scissor testing. When you render something and scissor testing is enabled then all fragments...
  5. What happened to me once was that I did something...

    What happened to me once was that I did something wrong (illegal arguments to some OpenGL function) and wasnt checking for errors consistently and different drivers / GPUs reacted differently to the...
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    It wasnt really a practical question and more of...

    It wasnt really a practical question and more of a theoretical question. I was thinking that graphics card producers would try to optimize VAO's since they have been added to the specs and as time...
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    Is it true that VAO's are inefficient?

    Hi there,

    somebody told me recently that VAO's are inefficient (due to cache misses or something) and one should only use one global VAO for maximum efficiency. This sounds dubious to me and...
  8. Your code might be slow because you create lots...

    Your code might be slow because you create lots of java objects which need to be garbage collected.
    Could you show us the actual java code you use with your buffers? In general, when performance is...
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    What java library are you using for the OpenGL...

    What java library are you using for the OpenGL bindings?
    If it is LWJGL then your approach will not work as you need to set the buffers byte order and you also have to rewind it. If you are new to...
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    You can write your own shaders and use uniforms...

    You can write your own shaders and use uniforms for the alpha value.
  11. Thread: Simple question

    by Cornix
    Replies
    3
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    546

    Because multiplication with matrices is not...

    Because multiplication with matrices is not commutative. Do internet research on commutativity and matrices and you may learn more.
  12. In general you want to have as few OpenGL calls...

    In general you want to have as few OpenGL calls as possible, and you want to do many things at once. If you have many sprites, and they are all moving, just update the VBO data for all of them at...
  13. Of course it will. Just think about it, old...

    Of course it will. Just think about it, old applications have to run on newer hardware as well. So if you write a new application using old techniques it will run on new hardware just as well as old...
  14. No. You use the fixed functionality pipeline. In...

    No.
    You use the fixed functionality pipeline. In the fixed function pipeline you will always take the fragment color from the highest enabled texture when rendering. The texcoords will be the last...
  15. Have you disabled textures before drawing the...

    Have you disabled textures before drawing the point? Otherwise you will try to sample texcoords from the texture, even when drawing a point or a line.
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    If you want good performance then immediate mode...

    If you want good performance then immediate mode (the glBegin ... glEnd stuff) is probably not what you want to do. It is old and deprecated, mainly because it is slow.
    If you want to improve...
  17. Thread: GLSL questions

    by Cornix
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    1,074

    Why dont you just try it out? You have a...

    Why dont you just try it out? You have a compiler, just ask it what is allowed.
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    You can use the same shaders for various...

    You can use the same shaders for various rendering operations.
    If you want to show 1000 images but they all use the same kind of information you only need a single shader.

    You can also draw all...
  19. OpenGL is not responsible for creating windows....

    OpenGL is not responsible for creating windows. That is a platform dependent task which is usually done by a third party library. And just having multiple windows is not killing frame rates either....
  20. How about you just try it and see how the...

    How about you just try it and see how the performance is before making assumptions. You could even try different approaches and pick the one with the most promising results.
  21. How often do you need to remove these meshes? If...

    How often do you need to remove these meshes? If it isnt too often or you dont have too many meshes then simply rebuild the entire VBO from ground up.
    Uploading a few kb of data isnt that slow...
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    You could test if your depth testing is...

    You could test if your depth testing is initialized correctly by just drawing 2 lonely triangles over each other and see whether the correct one gets displayed.
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    Why should it not be? The developers make it for...

    Why should it not be?
    The developers make it for fun and their personal enjoyment and share their work with others. Not everybody wants to have money, some prefer personal satisfaction.
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    Perhaps you should instead look at a full blown...

    Perhaps you should instead look at a full blown engine like libGDX which will do these things for you. If you are a beginner it might be very though to do everything by scratch.
  25. Not everybody speaks english as their native...

    Not everybody speaks english as their native language, its a big world, it might very well be that you do not know what translation means.
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