>>2873419Duplicating faces also exacts a toll on performance even if they are hidden (lower toll if the material is not being rendered), but I guess you'll find it negligible if you aren't using one of those super-high-poly clothing models and have a decent rig. Furthermore, morphs also have a performance cost.
Testing conditions: single model doing the 挑発ぶるんぶるんre "dance" with unlimited FPS, RTX 2060 6 GB / 16 GB RAM / Ryzen 7 2700X. duplicating all faces of all materials brings the count up to 333,724 (with 106,521 vertices) in MMM and 189,414 for the MMD-compatible version (57,626 vertices).
1) With a barebone Ray-MMD for MMM setup, the performance in motion dropped from 8 to 4 at the start and from 4 to 2 fps further on.
2) In a blank MMM scene, from ~93 to ~32.
3) 42 fps vs 31 fps (not recompared in MMM) in a set-up ムムム's indoor pool scene with a wet skin material assigned to the model.
4) ~290 vs ~250 fps in a blank MMD scene (and 215 vs 97 fps when using the MMD versions in MMM; however, if I turn off rendering for the duplicate materials, it rises to 164 fps).
5) ~380 FPS and ~315 FPS if I delete the remaining 248 morphs. ~250 FPS if I duplicate both vertices & faces instead of just faces after deleting all morphs. File sizes: 3.283 KB, 3.844 KB, 7.628 KB respectively.
https://youtu.be/oLO9Jc5NjUs?si=CAaYO_EIoQlY2qua&t=8