Open worlds

Target: tens of thousands of objects over kilometres, mostly static.

• Camera-relative tracing (rendering/pathtracing/relative_origin_grid): exact shadows and reflections far from the origin.
• Persistent instances (rendering/pathtracing/persistent_instances): unchanged objects and MultiMeshes cost no per-frame work.
• Off-screen culling (rendering/pathtracing/cull_max_distance, cull_min_size): small or distant unseen objects leave the trace.
• Opacity micromaps (rendering/pathtracing/opacity_micromaps): cut-out foliage traced without any-hit shaders.
• Mesh LOD in the path tracer (rendering/pathtracing/mesh_lod).

Settings for a large world, in project.godot:

[rendering]
pathtracing/relative_origin_grid=1024.0
pathtracing/persistent_instances=true
pathtracing/cull_max_distance=500.0
pathtracing/cull_min_size=0.1
pathtracing/opacity_micromaps=true

Test scene (2 km, prints timing and memory):

godot --path docs/bench/open_world --gpu-profile -- --count=100000 --set=rendering/pathtracing/persistent_instances:1

Options: --movers=N, --churn=N, --recolor, --fly=S, --multimesh=M (MultiMesh tiles of M meters), --mmmove=N, --raster, --out=frame.png. Design and measurements: open-world geometry, persistent instances, instanced forests, opacity micromaps.