Adds a dedicated `visibility: array<u32>` storage buffer (binding 4)
alongside the existing batched hatch buffers. Vertex shader reads
`visibility[v.instance_index]` — 0 → emit an out-of-NDC clip
position so the GPU rasterizer clips the primitive before the
fragment stage runs.
`compute_hatch_lod` now drives this buffer instead of (or alongside,
for the per-hatch fallback) `hatch_skip_flags`. Walks a per-instance
CPU AABB mirror that the builder fills at upload time (`instance_aabbs`),
applies the same `aabb_below_pixel` (sub-pixel LOD) OR `aabb_offscreen`
(frustum cull) rule the legacy path used, and pushes the resulting
0/1 flags via `queue.write_buffer` on a separate 4 B-per-hatch buffer
— ~40 KB per pan tick for 10 k hatches, far cheaper than re-writing
the 112 B-per-instance data.
Step 5 will remove the legacy `gpu_hatches` Vec, the per-hatch draw
loop, and `hatch_skip_flags` once the batched path has soaked.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Two issues in the step-3 batched path surfaced during testing:
1. WGSL rejects compile-time NaN literals (`0.0 / 0.0`), so the
visibility-skip path that emitted a NaN clip position failed
`Device::create_shader_module` validation. Replaced with an
out-of-frustum clip position `(2, 2, 2, 1)` — the GPU rasterizer
clips the primitive and the fragment shader never runs.
2. Pattern hatches rendered with the wrong spacing / direction. The
batched builder was rotating `perp_step` / `along_step` into the
global frame, but the per-hatch shader (`hatch.wgsl`) expects them
in QCAD PAT local-frame convention: `perp_step = family.dy`,
`along_step = family.dx`, with the cos_off/sin_off rotation applied
inside the shader. Now matches `build_family_batch` from
`hatch_gpu.rs` line-for-line. `line_width` also reset to 0 (the
shader picks 1 px from a screen-space derivative; the stored field
is unused).
3. Padding's `max_spacing` likewise dropped its bogus rotation and
now uses `|dy|` per family, matching the new perp_step convention.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Stand-alone module — no consumers yet. Packs an entire `&[HatchModel]`
into four storage buffers + a per-vertex (corner, instance_index)
stream:
- `InstanceBuffer` — `HatchInstance[]` (112 B each): color, mode,
gradient params, world_origin, local-space aabb, boundary range,
family range, visibility flag.
- `BoundaryBuffer` — flat `vec4<f32>[]` (NaN markers preserved as
per-path separators, just like the per-hatch shader expects).
- `FamilyBuffer` — flat `LineFamilyGpu[]` (matches the per-hatch
family layout one-for-one apart from `dash_offset` indexing into a
separate dash buffer).
- `DashBuffer` — flat `f32[]`.
The per-vertex buffer holds `6 × instance_count` records of
`(corner: u32, instance_index: u32)`. Step 2 will add the matching
WGSL shader that uses these to project a per-instance AABB quad and
run the in-polygon test against `BoundaryBuffer[offset..offset+count]`.
iced reports 8 storage buffers per stage, 128 MB binding cap, 256 MB
buffer cap — plenty for ~10 k hatches × 112 B + ~32 MB boundaries.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
