Sorry, it is a secret recipe.
Ok, April
The best looking solution is to code a simple edge detector directly into the LFS post-processing shader.
However, this will not work online, because all players need to have the same shader. Therefore I made up a simple geometric workaround. The black contour is just a blackened and up-scaled model of the car body which encapsulates the actual body. The LFS uses (almost every game does) a back-face culling optimization technique - the triangles can be seen from only one side (if not set otherwise). To prevent contour from hiding the actual body, it has simply flipped normals (triangles). Therefore, only the back side of the contour is being rendered.
There are several limitations of this method:
- it creates characteristic artefacts on non-convex objects
- it may stop working in the future due to LFS graphical updates (may spoil dynamic lights or the environment mapping for example)
- it is suitable for low-poly models only
As far as I know, currently this mod is the only one with such graphical feature. But who knows, maybe this recipe will inspire some other modders
