[Compute Shader] Porting an Image Effect Shader - Kuwahara Filter

Questions & Answers
1

Hi All I am trying to port an image Effect Shader to Compute Shader because I want to learn compute shaders. I chose to port Kuwahara Filter because I am generally interested in image filtering. Below is my port which give a black screen. Any help will be appreciated as I am very new to this and there isn’t much info on the subject around. The original image effect shader is in the link above.

// 
#pragma kernel CSMain
#include "UnityCG.cginc"


// Create a RenderTexture with enableRandomWrite flag and set it
// with cs.SetTexture

Texture2D<float4> Source;
RWTexture2D<float4> Destination;
int Radius = 5;
SamplerState samplerSource;

[numthreads(8,8,1)]
void CSMain(uint3 id : SV_DispatchThreadID)
{


	float3 mean[4] = {
	{ 0, 0, 0 },
	{ 0, 0, 0 },
	{ 0, 0, 0 },
	{ 0, 0, 0 }
	};

	float3 sigma[4] = {
		{ 0, 0, 0 },
	{ 0, 0, 0 },
	{ 0, 0, 0 },
	{ 0, 0, 0 }
	};

	float2 start[4] = { { -Radius, -Radius },{ -Radius, 0 },{ 0, -Radius },{ 0, 0 } };


	float2 pos;
	float3 col;
	uint width;
	uint height;
	uint levels;
	Source.GetDimensions(0, width, height, levels);

	float widthf = (float)width;
	float heightf = (float)height;


	for (int k = 0; k < 4; k++) {
		for (int i = 0; i <= Radius; i++) {
			for (int j = 0; j <= Radius; j++) {
				pos = float2(i, j) + start[k];
				col = Source.SampleLevel(samplerSource, float2(pos.x * 1.0/width, pos.y * 1.0/height), 0);
				mean[k] += col;
				sigma[k] += col * col;
			}
		}
	}

	float sigma2;

	float n = pow(Radius + 1, 2);
	float4 color = Source[id.xy];
	float min = 1;

	for (int l = 0; l < 4; l++) {
		mean[l] /= n;
		sigma[l] = abs(sigma[l] / n - mean[l] * mean[l]);
		sigma2 = sigma[l].r + sigma[l].g + sigma[l].b;

		if (sigma2 < min) {
			min = sigma2;
			color.rgb = mean[l].rgb;
		}
	}

	Destination[id.xy] = color;

}
2

bit of a late reply, but this works for me:

#pragma kernel CSMain
#include "UnityCG.cginc"

Texture2D<float4> source;
RWTexture2D<float4> output;

int _Radius = 10;
SamplerState sampler_source;

[numthreads(8, 8, 1)]
void CSMain(uint3 id : SV_DispatchThreadID)
{
    float3 mean[4] = {
    { 0, 0, 0 },
    { 0, 0, 0 },
    { 0, 0, 0 },
    { 0, 0, 0 }
    };

    float3 sigma[4] = {
    { 0, 0, 0 },
    { 0, 0, 0 },
    { 0, 0, 0 },
    { 0, 0, 0 }
    };

    float2 start[4] = { { -_Radius * .5, -_Radius * .5},{ -_Radius * .5, 0 },{ 0, -_Radius * .5},{ 0, 0 } };

    float2 pos;
    float3 col;
    
    for (int k = 0; k < 4; k++) {
        for (int i = 0; i <= _Radius; i++) {
            for (int j = 0; j <= _Radius; j++) {
                pos = float2(i, j) + start[k];
                col = source[id.xy + uint2(pos.x, pos.y)];
                mean[k] += col;
                sigma[k] += col * col;
            }
        }
    }

    float sigma2;

    float n = pow(_Radius + 1, 2);
    float4 color = source[id.xy];
    float min = 1;

    for (int l = 0; l < 4; l++) {
        mean[l] /= n;
        sigma[l] = abs(sigma[l] / n - mean[l] * mean[l]);
        sigma2 = sigma[l].r + sigma[l].g + sigma[l].b;

        if (sigma2 < min) {
            min = sigma2;
            color.rgb = mean[l].rgb;
        }
    }

    output[id.xy] = color;

}

188564-image-2021-11-11-071457.png

3

Not too late :slight_smile: Thanks! I will check it out. Also, you another new thing that you might want to Check out is a library called ComputeSharp (not unity related)