【Unity】ComputeShaderでMax-Minフィルタを実装してみる【Q13】

#pragma kernel MaxMinFilter

RWTexture2D<float4> Result;
Texture2D<float4> Texture;

[numthreads(32,16,1)]
void MaxMinFilter (uint3 id : SV_DispatchThreadID)
{
    float4 rgb2gray = float4(0.2126, 0.7152, 0.0722, 0);

    float gray[9] = {
        dot(Texture[id.xy + int2(-1, 1)],rgb2gray),
        dot(Texture[id.xy + int2(0, 1)],rgb2gray),
        dot(Texture[id.xy + int2(1, 1)],rgb2gray),
        dot(Texture[id.xy + int2(-1, 0)],rgb2gray),
        dot(Texture[id.xy],rgb2gray),
        dot(Texture[id.xy + int2(1, 0)],rgb2gray),
        dot(Texture[id.xy + int2(-1, -1)],rgb2gray),
        dot(Texture[id.xy + int2(0, -1)],rgb2gray),
        dot(Texture[id.xy + int2(1, -1)],rgb2gray)
    };

    float maxValue = max(gray[0],max(gray[1], max(gray[2], max(gray[3], max(gray[4], max(gray[5], max(gray[6], max(gray[7], gray[8]))))))));
    float minValue = min(gray[0],min(gray[1], min(gray[2], min(gray[3], min(gray[4], min(gray[5], min(gray[6], min(gray[7], gray[8]))))))));

    float target = maxValue - minValue;

    Result[id.xy] = float4(target, target, target, 1);
}

C#側のコードはこちら。

using UnityEngine;
using UnityEngine.UI;

public class MaxMinFilter : MonoBehaviour
{
    [SerializeField] private ComputeShader _computeShader;
    [SerializeField] private Texture2D _tex;
    [SerializeField] private RawImage _renderer;

    struct ThreadSize
    {
        public uint x;
        public uint y;
        public uint z;

        public ThreadSize(uint x, uint y, uint z)
        {
            this.x = x;
            this.y = y;
            this.z = z;
        }
    }

    private void Start()
    {
        if (!SystemInfo.supportsComputeShaders)
        {
            Debug.LogError("Comppute Shader is not support.");
            return;
        }

        // RenderTextueの初期化
        var result = new RenderTexture(_tex.width, _tex.height, 0, RenderTextureFormat.ARGB32);
        result.enableRandomWrite = true;
        result.Create();

        // カーネルインデックスを取得
        var kernelIndex = _computeShader.FindKernel("MaxMinFilter");

        // 一つのグループの中に何個のスレッドがあるか
        ThreadSize threadSize = new ThreadSize();
        _computeShader.GetKernelThreadGroupSizes(kernelIndex, out threadSize.x, out threadSize.y, out threadSize.z);

        // GPUにデータをコピーする
        _computeShader.SetTexture(kernelIndex, "Texture", _tex);
        _computeShader.SetTexture(kernelIndex, "Result", result);

        // GPUの処理を実行する
        _computeShader.Dispatch(kernelIndex, _tex.width / (int)threadSize.x, _tex.height / (int)threadSize.y, (int)threadSize.z);

        // テクスチャを適応
        _renderer.texture = result;
    }
}