ApproximateActors: add FMeshApproximationSettings::bEnableSimplifyPrePass option, default true, and implement in ApproximateActors impl. This does a fast-collapse down to a multiple of the target triangle count (or 1m tris in tolerance-mode). This reduces simplification time in HLOD builds for small city from 4-5m to 1m in some of the worst blocks.
ApproximateActors: add FMeshApproximationSettings::bEnableParallelBaking, default true, and implement in the ApproximateActors Impl. This allows the photocapture step to proceed at the same time as the mesh generation, which shaves 30-40s off every HLOD build, but increases memory requirements.
#rb sebastien.lussier
#jira UE-142582
#preflight 6214fd9e797dbbeb4723468e
#rnx
#ROBOMERGE-AUTHOR: ryan.schmidt
#ROBOMERGE-SOURCE: CL 19083146 in //UE5/Release-5.0/... via CL 19097574
#ROBOMERGE-BOT: UE5 (Release-Engine-Staging -> Main) (v921-19075845)
[CL 19141130 by ryan schmidt in ue5-main branch]
