System Information
Operating system: Windows-10-10.0.17763 64 Bits
Graphics card: GeForce GTX 1050 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 436.30
Blender Version
Broken: version: 2.81 (sub 13), branch: master, commit date: 2019-10-02 21:39, hash: rB93e8c962fcc1
Worked: (optional)
Short description of error
Solidify modifier's material index offset no longer does anything.
Exact steps for others to reproduce the error
Add object. Add Solidify modifier to it. Set offset to 1. Add 2 materials.
Only first material will be applied.
Note, that rim can use second material, but not the duplicated geometry.
In fact, there isn't any original geometry left. And if you swap material slots, rim won't use second material anymore, yet geometry will work.