bench-resize-gate

name	bench-resize-gate
description	When a Titan bench tool using Renderer3d lacks on_resize → renderer.resize(), depth_prepass_view and HZB occlusion resources are never created — DepthPrepass, HzbBuild, and SceneCull passes silently skip, and taps produce no output
source	auto-skill
extracted_at	2026-06-16T04:02:21.935Z

Bench Resize Gate

When a Titan bench tool creates a Renderer3d but never calls renderer.resize(), several rendering subsystems silently fail because their resources are only allocated inside Renderer3d::resize().

The trap

depth_prepass_view, depth_prepass_texture, and hzb_occlusion_resources are created inside Renderer3d::resize(), gated by self.fg.depth_prepass_pipeline.is_some(). The depth prepass pipeline IS created during frame graph build (before the first render), but its view and texture are NOT — they wait for resize().

If resize() is never called:

• depth_prepass_view stays None → the DepthPrepass pass arm does continue before rendering any depth or reaching the tap dispatch code
• hzb_occlusion_resources stays None → HzbBuild is never dispatched → SceneCull reads an uninitialized zero-filled HZB where every texel is 0.0 (far plane under reverse-Z), so no candidate is ever occluded
• Tap output for depth_prepass, scene_indirect_draws, and scene_cull_visibility is never produced because the dispatch code is never reached

The symptom is silent: the bench runs, the window appears, geometry renders (via GBufferFill's fallback draw_indexed path), but HZB occlusion scores are always "visible" and taps produce zero output files.

The fix

Add fn on_resize to the bench's App impl, matching the probe bench pattern:

fn on_resize(&mut self, width: u32, height: u32) {
    if let Some(ref mut renderer) = self.renderer {
        renderer.resize(width, height);
    }
}

Why this is easy to miss

Renderer3d::new creates the device, surface, swapchain, and frame-graph pipelines. It looks like a complete initialization. The resize() call looks redundant for a non-resizable window — the initial size is already known. But resize() is where the depth prepass texture + view + HZB chain are actually allocated.

Verification

After adding on_resize, verify with:

cargo run -p titan-render-bench-culling --features debug-dumps -- \
  --duration 3 --warmup 5 --tap depth_prepass --dump-window 5..7 --dump-once

Expected: titan-dumps/depth_prepass-frame5.bin (or frame6) is created. CSV should show hzb_occluded entries for geometry behind occluders.