source: code/archive/skybox/Media/materials/programs/hdr_bloom.glsl

uniform sampler2D inRTT;

uniform vec4 sampleOffsets[15];
uniform vec4 sampleWeights[15];

varying vec2 uv;

void main(void)
{
    vec4 accum = vec4(0.0, 0.0, 0.0, 1.0);
        vec2 sampleUV;
    
    for( int i = 0; i < 15; i++ )
    {
        // Sample from adjacent points, 7 each side and central
        sampleUV = uv + sampleOffsets[i].xy;
        accum += sampleWeights[i] * texture2D(inRTT, sampleUV);
    }
    
    gl_FragColor = accum;
        
}