How to use stencil test

[dubois]

Stencil projection demo

I had an interview recently and we discussed how would one project this spline representing a vehicles trajectory onto uneven terrain. I proposed something like stencil shadows instead of textures. This is a demo of that - there is a spline that can be moved, it’s above the terrain, and it projects a shadow basically. It’s not the whole stencil shadow algorithm since it doesn’t compute any contours and such, but the way it writes to stencil is borrowed from there. Link