I am using Direct3D 9 (for testing stuff)
The geometry is fine, but the u, v all breaks, I think the original uvs are good for the submeshes only, the material id also breaks (turns to zero), basically means I can't tell which subset is which... how can I solve this?
thanks
Jack

show us your code for collapsing, it's hard to tell what the issue is, just by your words.

42 minutes ago, Krypt0n said:

show us your code for collapsing, it's hard to tell what the issue is, just by your words.

Also, study some small test, e.g. "collapsing" two tetrahedra. or two cubes. Comparing the desired result (which you can compute easily) with your defective mesh operation should be very instructive.