uniform sampler2D SCREEN_TEXTURE;
uniform highp float Strength;
const highp int SampleCount = 10; // a higher number makes the shader look better, but has a big performance impact

// a simple radial blur
void fragment() {
    highp vec3 col = texture(SCREEN_TEXTURE, UV).xyz;
    highp vec4 color = zTexture(UV);
    highp vec2 direction = vec2(0.5, 0.5) - UV;
    for (int i=1; i <= SampleCount; i++)
    {
        col += zTextureSpec(SCREEN_TEXTURE, UV + float(i) * Strength / float(SampleCount) * direction).xyz;
    }
    col = col / float(SampleCount);
    COLOR = vec4(vec3(col), color.a);
}