I’m going with the patch mesh just above (1 unit) the surface I want the decal to appear.
I won’t be projecting it onto the surface beneath using the entity method.
I have to keep my eye on the number of entities since I’m getting fairly high up in the count.
I did get the entity method working thanks to ShaderMan.
There is nothing bad about CSG Subtract, I use it all the time. I never do it on ready textured brushes, I always cualk things, then CSG Subtract, then texture. I have no problems with it.
In theory it’s nothing wrong with csg subtract, in practice it might not produce the best results. If you know what you do, and only use it for simple structures it can be a time saver. But more often than not, the result is far from perfect where manual cuts would produce far better results, with less overdraw and simpler brushwork. Usually IF you use CSG subtract, you still need to optimise the brushwork after the subtract which makes it more or less redundant.