It should work for either MESHES = or MATERIALS = if they're named correctly. It's often easier specifying material names because (for example) external bodywork often has one material name for the complete bodywork, but different mesh names for each panel.
Adding CULL_MODE = DOUBLESIDED is useful to visually help to plug holes in the cockpit if things like rubber seals are one-sided.
For example, on the recent E21 BMW/Alpina pack, some gaps through to the road can be sort-of hidden with:
Code:
;stop sun ingress around cockpit mesh seams, into footwells etc
[SHADER_REPLACEMENT_...]
ACTIVE = 1
MATERIALS = matt colors?, Black, BODY; external bodywork, trim, pillars, dashboard etc
MESHES =
CULL_MODE = DOUBLESIDED
CAST_SHADOWS = 1
DOUBLE_FACE_SHADOW_BIASED = 1
This just doublesides materials so that (for example) the door skin is no longer transparent from the cockpit side, so the road can no longer be seen through the gap at the top of the door cill... but you do see the door paint on the inside of the door through the gap. Which is not ideal, but IS better than seeing the road. Works best with dark car paints.
Configs like this are a bandaid with mixed results, treating the symptom rather than the disease. The modder really needs to take more care to ensure that gaps like this are properly sealed in the actual model.
Edit: by the way, on the subject of those E21 BMWs, the ones that don't have a right-side mirror but do have a few mirror mesh artefacts still floating around on that side need:
Code:
;useful for hiding stuff
[MESH_ADJUSTMENT_...]
MESHES=R Mirror?
IS_RENDERABLE=0
drive.google.com
