Overprint Screen Shader

I’ve got a background in graphic design and illustration and wanted to do a project that marries digital and analog graphics. I was inspired by risograph printing and other printing techniques where colors overlay each other and allows the underlaying colors to shine trough.

I created this post processing effect in unreal which separates parts of the scene in to a number of “layers” depending on the brightness of the pixels. Each layer except from the brightest layer is then multiplied with the underlying layer to create an effects of colors that are mixed together. This means that when the darkest layers color is changed, only the darkest parts will change color, while if the lighter layers colors are changed all of the darker layers will change color based on the new mix of colors.

I also decided to create a knock out print effect which is more like an ordinary toon shader in the way that layers are not mixed. It still separates the scene in different brightness layers but here the colors are opaque and does not multiply. To make it possible for more variation i added outlines that are either the same stroke weight or changes stroke weight based on the distance from the camera, making closer lines thicker and lines further away thinner. I built an interface with buttons and sliders that controls and visualizes the colors used in the scenes and a toggle between two different scenes. All the scene assets are made in Blender by me.

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