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Thread: Display algorithm in Fragment Shader

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  1. #1
    Newbie Newbie
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    Apr 2014
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    Display algorithm in Fragment Shader

    I am new in OpenGL, recently, I am using OpenGL ES to process real time video frame(frame size if about 800 * 600, target GPU is PowerVR SGX543/266 MHz). In this project, we anlyse data of pixel cluster and display the pixel with an algorithm (for example, make a Gaussian Blur algorithm). In my design, the algorithm is implemented in the Fragment Shader(Time Complexity is O(n*n)), it works, but the frame rate is too low, The normal frame rate is about 60 fpt, when enable the algorithm, frame rate become to 2 fpt.
    My question is: "algorithm implemented in the Fragment Shader", is this pattern correct? It seems absolute to fall down the frame rate.

  2. #2
    Advanced Member Frequent Contributor
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    Dec 2007
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    Hungary
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    Yes, you should use fragment shader, especially because your target GPU doesn't support compute shaders (which could be an alternative).

    Your problem is that you use n*n fetches in your fragment shader. But this is not the most efficient way.

    You should use a 2-pass separable Gaussian filter then you can reduce the number of fetches to 2*n. Also there are other techniques to reduce the fetch count.

    For more information check this article.
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  3. #3
    Newbie Newbie
    Join Date
    Apr 2014
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    aqueous, thanks your reply, it's very helpful for me.

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