// At first glance it looks like I'm doing nothing, but remember the order of operations vec4 brightnessFilter(vec4 input_colour) { vec4 col = vec4(0.0); col.r = max(input_colour.r + input_colour.r / 2.0, 0); col.g = max(input_colour.g + input_colour.g / 2.0, 0); col.b = max(input_colour.b + input_colour.b / 2.0, 0); col.w = 1.0; return col; }