v0.12.0

Performance

• Arc-backed surface submission: SurfaceSubmission::Flat now holds Arc<[SceneRenderItem]> instead of Vec; per-frame cost for a static scene drops from a full deep-copy (~150 MB/frame at 1M objects) to a single atomic refcount increment. New SceneFrame::from_shared_items constructs a frame directly from a caller-owned Arc with no allocation.
• Async scene build: large scene construction runs on a background thread; the UI thread stays live during the build. Completion is delivered via mpsc::channel::try_recv. A LoadingBarItem overlay drives a live progress bar fed by an Arc<AtomicU32> counter incremented every 10 000 objects.
• Parallel BVH construction: build_bvh_node uses rayon::join for subtrees above 1 024 entries, cutting build time ~8x on multi-core hardware (~3 s -> ~400 ms for 1M objects)

Features

• GPU-driven culling: compute cull pass replaces the CPU BVH instanced culling path
  • cull_instances compute shader tests per-instance world-space AABBs against the camera frustum; visible instances are compacted into a visibility index buffer via atomic slot claims
  • write_indirect_args compute shader writes one DrawIndexedIndirect entry per batch and resets atomic counters for the next frame
  • Main pass and OIT pass use draw_indexed_indirect; vertex shaders read through the visibility index buffer via a vs_main_cull entry point
  • Shadow cascade extension: each cascade gets its own GPU cull dispatch (per-cascade frustum, per-cascade visibility buffer) and indirect draw; the CPU per-item frustum loop in the instanced shadow path is replaced
  • Automatic activation: GPU culling is on by default when the device supports INDIRECT_FIRST_INSTANCE; silent fallback to direct draw on devices that do not
  • disable_gpu_driven_culling() / enable_gpu_driven_culling() runtime toggle on ViewportRenderer
  • FrameStats::gpu_culling_active: reports which draw path ran each frame
• Showcase 3 (Performance at Scale): live GPU culling toggle, full FrameStats readout (CPU/GPU timings, culled count, draw path, render scale, upload bytes)