How To Add Colored Shadow Penumbra In Unreal Engine 5

Oscar Sanz, Senior Technical Artist at CD Projekt Red, has written a blog post.

Chosker

Even if you don't know the term, you've probably noticed the effect itself, often visible in the penumbra of an image and often exaggerated by artists. It's the soft, transitional edge of a shadow that gets additional color, and it's an important technique artists use to add visual clarity to their work.

3D is no different. If you want to add colored shadow penumbra to your Unreal project, Oscar Sanz, also known as Chosker, has written a guide explaining how to implement it by editing the shaders. He was inspired by this project from Romain Durand:

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A post shared by Romain Durand (@rdurandart)

If you're interested in the theory, read this Medium article by Shahriar Shahrabi.

Chosker explains that his approach is fairly simple to implement and avoids the need to guess light and shadow values like a post-process solution, which can be especially tricky with Lumen or day/night cycles. It also works with all light types and is very lightweight in terms of performance. However, the color saturation can only be adjusted globally rather than per light or scene, the effect needs wide penumbras to be noticeable, and it only works with dynamic lights, not baked lighting.

You only need to edit the engine shaders, so you can stick with the launcher version. If you're not familiar with how engine shader files can be edited, check out this Chosker's article to learn more and get started. Read the article on the implementation of colored shadow penumbra here.