Cairn - Technical Breakdown - Wall Clippers
I was lucky to work on Cairn as Technical Art Director, I thought it might be interesting to share some of its "development secrets".
This one is about a little technique we used to fake small boolean operations on rocks.
More about Cairn :
https://www.thegamebakers.com/cairn/
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A little write about the technique we used to render inner holds on walls in Cairn.
https://www.thegamebakers.com/cairn/
Additionals holds/cracks are drawn in editor on walls, and we want to have "inner" holds.
When you want to carve something or create a hole in 3D, the first thing that come in mind is boolean operations.
But it is slow, can crash and the result is not always optimal.
We use it a very little in Cairn and only at a macro level design stage.
For tiny subtractions like holds, we go for another method I called WallClippers:
First we need to remove/clip the parts we want to carve.
To do so, we project all vertices of our holds meshes on the wall (baked static mesh) and render them at runtime to a depth buffer.
Rock shader compares its own depth with this depth buffer, if they are close enough, let's discard this fragment.
Then we render our crack/hold mesh over this hole. This hold is a lie ! (well, doesn't exist for physx)
various gbuffers :
[normals] [material ids] [edge detection removal] [wall clippers depth]
only the last one is used for this method (others are just here for vizualisation)
and something way more interesting is what level artists do with your tech stuff initially designed for little tiny cracks :)