Unreal 5.6 - Kuwahara
Post-Process Technique

KUWAHARA 5.6

Music by Simon Henry - Sometime Ago

The Kuwahara Post Process technique is an imaging technique, originally developed by Michiyoshi Kuwahara.

A doctor working on the university of Kyoto, Japan, in the 1970’s.

In unreal engine, it’s used artistically to simulate a painted environment.

There are many versions of the Kuwahara filter for UE 5.6

however, in my version I add the ability to
add a texture to simulate a canvas, and it’s quite literally how I start the base of my paintings.

Like in this case — “The Gardener”

In order to save time, I scult as normal,
or model a mesh, create a depth map and apply the filter.


I now have a solid color-base to begin painting in photoshop as normal with my brushes and ComfyUI.

Saving me time, making the process efficient and above all, working smartly.
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003.png
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005.png
hands.png
hands_final.png

KUWAHARA CODE

Custom Node

Unreal 5.6

//Kuwahara UE5.6 Version by Joshua Balcaceres //www.balcaceres.art

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 offsets[4] = {{-RADIUS.x, -RADIUS.y}, {-RADIUS.x, 0}, {0, -RADIUS.y}, {0, 0}};

float2 pos; float3 col;

float gradientX = 0; float gradientY = 0;

float sobelX[9] = {-1, -2, -1, 0, 0, 0, 1, 2, 1}; float sobelY[9] = {-1, 0, 1, -2, 0, 2, -1, 0, 1};

int index = 0; float2 texelSize = 1.0/VIEWSIZE;

for(int x = -1; x <= data-preserve-html-node="true" 1; x++) { for(int y = -1; y <= data-preserve-html-node="true" 1; y++) { if(index == 4) { index++; continue; }

    float2 offset = float2(x, y) * texelSize;
    float3 pxCol = SceneTextureLookup(UV + offset, 14, false).xyz;
    float pxLum = dot(pxCol, float3(0.2126, 0.7152, 0.0722));

    gradientX += pxLum * sobelX[index];
    gradientY += pxLum * sobelY[index];

    index++;

}

}

float angle = 0;

if(abs(gradientX) > 0.001) { atan(gradientY / gradientX); }

float s = sin(angle); float c = cos(angle);

for(int i = 0; i < 4; i++) { for(int j = 0; j <= data-preserve-html-node="true" RADIUS.x; j++) { for(int k = 0; k <= data-preserve-html-node="true" RADIUS.y; k++) { pos = float2(j, k) + offsets[i]; float2 offs = pos * texelSize;

        offs = float2(offs.x * c - offs.y * s, offs.x * s+ offs.y *c);

        float2 uvpos = UV + offs;
        col = SceneTextureLookup(uvpos, 14, false);

        mean[i] += col;

        sigma[i] += col * col;

    }

}

}

float n = (RADIUS.x+1) * (RADIUS.y+1); float sigma_f; float min = 1;

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

if(sigma_f < min)
    {
        min = sigma_f;
        col = mean[i];
    }

}

return col;