shader_type canvas_item;

uniform int levels = 3;
uniform float spread = 0.01;
uniform sampler2D SCREEN_TEXTURE : hint_screen_texture, filter_linear_mipmap;


void fragment(){
    vec3 sum;
    COLOR.rgb = vec3(0);
    vec2 offset = (UV - vec2(0.5))*vec2(1,-1);
    for(int i = 0; i < levels; i++){
        float t = 2.0*float(i)/float(levels-1); // range 0.0->2.0
        vec3 slice = vec3(1.0-t, 1.0 - abs(t - 1.0), t - 1.0);
        slice = max(slice, 0.0);
        sum += slice;
        vec2 slice_offset = (t-1.0)*spread*offset;
        COLOR.rgb += slice * texture(SCREEN_TEXTURE, SCREEN_UV + slice_offset).rgb;
    }
    COLOR.rgb /= sum;
}