PhysX tip: use the new Opcode2-based midphase structure
PhysX 3.4 has a new mesh structure based on Opcode 2, which is used for the “midphase” queries (i.e. any collision query against a triangle mesh).
It is not enabled by default because it currently has some limitations compared to the previous midphase structure:
- it does not support deformable meshes (i.e. it does not support PxTriangleMesh::getVerticesForModification() and PxTriangleMesh::refitBVH())
- it is not implemented on all platforms. It is currently only available on platforms for which PX_INTEL_FAMILY is defined (that includes PCs but also consoles like the Xbox One and PS4).
To enable it, look up the comments for PxCookingParams::midphaseDesc and the PxMidphaseDesc class. Or check the PhysX manual. Or the PEEL code. Basically it will come down to simply adding this line to the cooking params before passing them to PxCreateCooking:
PxCookingParams Params;
Params.midphaseDesc.setToDefault(PxMeshMidPhase::eBVH34);
Overall, the new structure should be faster than the previous one. It is also much faster to build, so if for some reason you must cook triangle meshes at runtime, this new structure should help. Memory usage should be roughly the same as before.
You can see the results in PEEL 1.1. The new midphase structure is selected by default in PEEL, but you can go back to the old one using the “cooking” tab in the PhysX 3.4 plugin’s UI. Note that Opcode 2 used as a standalone library still provides significantly faster results (you can see that in PEEL as well), because PhysX has a larger per-query overhead for management, filtering, etc.
The midphase structure is also used in rigid body simulation, for dynamic objects colliding against triangle meshes (to fetch candidate triangles). So switching to the new structure might also give you performance gains there, even if you are not using scene queries.