Read float values from RGBAFloat texture in Unity 3D

问题

It seems people aren't discussing much around floating point textures. I used them to do some computations and then forward the result to another surface shader (to obtain some specific deformations) and that's cool, it always works for me if I digest the results in a shader but this time I need to get those values CPU side so I get a float[] array with the results (just after calling Graphics.Blit that fills the floating point texture). How can this be achieved?

On a side note: the only guy that I saw using this method so far is Keijiro, for example in his Kvant Wall; if you have other sources I'd be grateful if you let me know.

Incidentally, I know there are compute shaders and OpenCL and CUDA. This is the method I need now.

回答1:

So I came up with this solution.

 float[] DecodeFloatTexture()
{
    Texture2D decTex = new Texture2D(resultBuffer.width, resultBuffer.height, TextureFormat.RGBAFloat, false);
    RenderTexture.active = resultBuffer;
    decTex.ReadPixels(new Rect(0, 0, resultBuffer.width, resultBuffer.height), 0, 0);
    decTex.Apply();
    RenderTexture.active = null;
    Color[] colors = decTex.GetPixels();
    // HERE YOU CAN GET ALL 4 FLOATS OUT OR JUST THOSE YOU NEED.
    // IN MY CASE ALL 4 VALUES HAVE A MEANING SO I'M GETTING THEM ALL.
    float[] results = new float[colors.Length*4];
    for(int i=0; i<colors.Length; i++)
    {
        results[i * 4] = colors[i].r;
        results[i * 4 + 1] = colors[i].g;
        results[i * 4 + 2] = colors[i].b;
        results[i * 4 + 3] = colors[i].a;
    }
    return results;
}

Alternatively, if what we need is not a float, GetRawTextureData can be used to then convert the bytes to the new type with System.BitConverter which gives some flexibility on the data you are passing from the shader (for example if your fragment shader is outputting half4). If you need float though the first method is better.

 float[] DecodeFloatTexture()
{
    Texture2D decTex = new Texture2D(resultBuffer.width, resultBuffer.height, TextureFormat.RGBAFloat, false);
    RenderTexture.active = resultBuffer;
    decTex.ReadPixels(new Rect(0, 0, resultBuffer.width, resultBuffer.height), 0, 0);
    decTex.Apply();
    RenderTexture.active = null;
    byte[] bytes = decTex.GetRawTextureData();
    float[] results = new float[resultBuffer.width * resultBuffer.height];
    for (int i = 0; i < results.Length; i++)
    {
        int byteIndex = i * 4;
        byte[] localBytes = new byte[] { bytes[i], bytes[i + 1], bytes[i + 2], bytes[i + 3] }; // converts 4 bytes to a float
        results[i] = System.BitConverter.ToSingle(localBytes, 0);
    }
    return results;
}

来源：https://stackoverflow.com/questions/40128185/read-float-values-from-rgbafloat-texture-in-unity-3d

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unity3d

gpgpu