My usual response is to sigh, and start explaining why we can’t do outlines like that. Or at least start talking to them about the kind of deep modi

The Quest for Very Wide Outlines

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Style Pass

2021-08-17 11:30:05

My usual response is to sigh, and start explaining why we can’t do outlines like that. Or at least start talking to them about the kind of deep modifications to the asset pipeline we would need to make this possible.

Of course my latest project is no different. But this time before I launched into my script on the differences between what Photoshop can do compared to the limitations of real time I had a thought.

This is a tale about trying to make very wide outlines for real time rendering. Attempting to over engineer and optimize the “bad” brute force way to see how fast I can get it. And then finally relenting and implementing the method I was willfully ignoring from the start.

One of the oldest and most used methods for adding outlines to any mesh is the inverted hull method. This has been used probably for as long as 3D rendering has been a thing. Just render the mesh twice, with the second version of it flipped inside out and slightly bigger. Jet Set Radio is an excellent early example of this technique. But it’s still used today to great effect, like any of the recent 3D fighting games from Arc System Works.

The methods for achieving a slightly bigger mesh are varied, but the most common method is to move the vertices out by the vertex normal. For very old games this would have been done outside of the game and there would simply have been two meshes, but today it’s most commonly done with shaders.