Configurable Box Blur

I could not find a good blur shader and just ended with learning the shader language. I used the post from Schorsch as a template https://godotforums.org/d/20506-a-good-blur-shader. He linked to a created shadertoy by him; so it might be that the license has to be changed?

I’m not very familiar with the shading language but I thought I read that GLES2 does not support for loops. So I gues this will work in Vulkan and GLES3.

Do note that this shader also blurs the alpha channel; something that is easily changed.

Bugfix, edge blur was incorrect. Looked at Exuin’s Blur.

Shader code
shader_type canvas_item;

uniform int strength: hint_range(1, 512) = 2;

vec4 blur_size(sampler2D tex,vec2 fragCoord, vec2 pixelSize) {
    
    vec4 color = vec4(0.,0.,0.,0.);
    float strengthFloat = float(strength);	

    vec2 pixel = fragCoord/pixelSize;
    int x_min = max(int(pixel.x-strengthFloat), 0);
    int x_max = min(int(pixel.x+strengthFloat), int(1./pixelSize.x));
    int y_min = max(int(pixel.y-strengthFloat), 0);
    int y_max = min(int(pixel.y+strengthFloat), int(1./pixelSize.y));

    int count =0;

    // Sum the pixels colors
    for(int x=x_min; x <= x_max; x++) {
        for(int y = y_min; y <= y_max; y++) {           
            color += texture(tex, vec2(float(x), float(y)) * pixelSize);
            count++;
        }
    }
    
    // Divide the color by the number of colors you summed up
    color /= float(count);
    
    return color;
}

void fragment() {	
    COLOR = blur_size(TEXTURE,UV,TEXTURE_PIXEL_SIZE);
}
Tags
blur
The shader code and all code snippets in this post are under CC0 license and can be used freely without the author's permission. Images and videos, and assets depicted in those, do not fall under this license. For more info, see our License terms.

Related shaders

Box Blur

Artsy Circle blur type thingy

Radial Blur Shader

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Ro
Ro
3 months ago

Thanks for that nice Shader. Works really well! 😉

Qtan1
Qtan1
2 months ago

Hi,
thanks for the amazing shader. I used it to create a dynamic depth of field effect: https://godotshaders.com/shader/dynamic-depth-of-field/

Calinou
1 month ago

I’m not very familiar with the shading language but I thought I read that GLES2 does not support for loops. So I gues this will work in Vulkan and GLES3.

for loops with a constant iteration count are guaranteed to work in GLES2/WebGL 1.0, but not when they have a variable iteration count. while loops won’t work either.