Ah I had just been applying the cel-shading to the character, the sky and the rest of the world were being rendered normally (passing PostProcessInput0 to the emissive out if custom depth isn’t used). I’ve been messing with Hue/Saturation but haven’t got it working yet, here’s a good resource on how to convert RGB to Hue/Saturation/Lightness: Math behind colorspace conversions, RGB-HSL – Niwa It’s now UE4 related, just an easy to follow overview of the maths involved.