marfrit
a4e7d8ab90
panvk-bifrost campaigns (r1..r4 Vulkan compositor + r5.video1 Vulkan
video decode) shipped before this repo existed; the deliverable
patches live in marfrit-packages, but the reasoning chain, phase docs,
and source-state evidence lived only in local working trees on the
development host.
This retrofit imports:
- mesa-panvk-bifrost/ — r1..r4 era phase docs (iter1..iter18)
(libmali stub blobs at iter18/blob/ excluded
— 109MB of RE artifacts replaced with a README
pointer)
- mesa-panvk-bifrost-video/ — sibling campaign phase docs + probe
- evidence/ — frozen .tgz source snapshots at each milestone
(basis for the 0005 patch diff generation)
Future iterations should branch off here from day one, so each iter is
a commit rather than a snapshot. See [[feedback-session-local-process-pins]]
for the process drift this retrofit closes.
Total: 1.9 MB across 124 files.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
3.3 KiB
3.3 KiB
Phase 0 — substrate for iter6
Opened 2026-05-19 after iter5 close GREEN.
Locked research question — iter6
Render a depth-tested scene into a 128×128 RGBA8 color attachment + 128×128 D32_SFLOAT depth attachment via dynamic rendering:
- Triangle A (red): large, NDC (-0.8,-0.8), (0.8,-0.8), (0.0,0.8), all with z=0.7
- Triangle B (green): small, NDC (-0.4,-0.4), (0.4,-0.4), (0.0,0.4), all with z=0.3 — fully geometrically inside Triangle A
- Draw A first, then B. Depth test enabled (
VK_COMPARE_OP_LESS).- Triangle B's lower z should make it appear in front of A wherever they overlap.
Verify specific pixels:
(0, 0)— clear (outside both, top-left corner)(127, 127)— clear (outside both, bottom-right corner)(64, 64)— inside both, GREEN (B in front)(64, 30)— inside A only (above B's reach in pixel-y), RED(64, 100)— inside A only (below B's reach), RED
Why this shape
iter5 closed all single-draw, no-depth, descriptor-binding paths. iter6 adds:
- Depth/stencil attachment (D32_SFLOAT) — new image format, new aspect, new usage flag (DEPTH_STENCIL_ATTACHMENT)
- Depth test + depth write in pipeline state (
VkPipelineDepthStencilStateCreateInfo) - Multi-draw within one render pass — two
vkCmdDrawcalls between begin/end - z-coordinate handling in the vertex shader (gl_Position.z affects depth)
- 128×128 image instead of 64×64 (more tiles — 8×8 grid of 16×16 = 64 tiles)
- Depth attachment format in
VkPipelineRenderingCreateInfoKHR.depthAttachmentFormat - Depth attachment in
VkRenderingInfoKHR.pDepthAttachment
Hypothesis space
- D32_SFLOAT depth format on Bifrost. Bifrost packs depth into tiles; the layout differs from color. First time we use a non-color attachment.
- Depth-stencil image creation + layout (
DEPTH_STENCIL_ATTACHMENT_OPTIMAL). New layout never used. - Depth test plumbing. PanVk-Bifrost's path from
VkPipelineDepthStencilStateCreateInfo→ tile descriptor depth-state fields. - Depth write back to depth attachment. Mali stores depth in tile memory then flushes; per-tile flush + cache invalidation.
- Multi-draw within one render pass. Bifrost's binner may have bugs handling N>1 jobs per render pass — particularly around per-draw state changes.
- z-coordinate from vertex shader. Vertex output position.z passes through to rasterizer.
- Tile binning at 128×128 (64 tiles vs. iter3's 16). More potential for binner state bugs.
In-scope (LOCKED 2026-05-19 for iter6)
- 128×128 RGBA8 color + 128×128 D32_SFLOAT depth attachment.
- 6 vertices (2 triangles) in one vertex buffer, vec3 pos + vec3 color.
- Depth test enabled, depth write enabled, compare LESS.
- Two
vkCmdDraw(3, 1, *, 0)calls within one render pass. - 5-point pixel-level verification.
Out-of-scope (LOCKED 2026-05-19 for iter6)
- Stencil (D32_SFLOAT has no stencil aspect anyway).
- D24_UNORM_S8_UINT or other depth formats (iter would explore if iter6 fails).
- Depth clear via load-op only (no separate clear-image).
- Front-face culling, polygon-mode lines.
- Indexed draws.
- More than 2 triangles.
- WSI / surface — still off-screen attachment + buffer readback.