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perf(scene): skip wire GPU re-upload when only the camera moved

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Phase 3.2 (wire pan path). Wire vertex buffers are world-space, so a
camera move changes only the view_proj uniform (uploaded every frame),
never the wire data — yet upload_wires re-ran on every camera_generation
tick, re-packing vertices and re-writing the GPU buffer on each pan.

Stamp every Model-tile re-tessellation with a monotonic content id
(WIRE_CONTENT_GEN), reused when a pan reuses the tessellation. The
pipeline records the resident buffer's id and skips upload_wires when the
incoming id matches. The gate is pulled out of the (epoch, camera_gen)
block so a preview/interim wire change still uploads even with a static
camera; non-tile paths and overlay frames force a fresh id, preserving
current behaviour. Monotonic id sidesteps the ABA hazard a freed/realloc'd
Arc pointer would carry.

Pairs with the pan tessellation reuse: a pan now skips both the CPU
re-tessellation and the GPU wire upload.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Hakan Seven 2026-06-05 09:16:44 +03:00
commit 0f40cfa054
4 changed files with 93 additions and 14 deletions
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50
src/scene/render.rs
View file

@ -74,9 +74,13 @@ pub struct ViewportData {
pub(super) hidden_line: bool,
pub(super) geometry_epoch: u64,
/// Camera generation captured when this Primitive was assembled. Paired
/// with `geometry_epoch` so the wire buffers re-upload when the view
/// changes (frustum culling produces a different wire list).
/// with `geometry_epoch` so the per-frame scissor / LOD recompute runs.
pub(super) camera_generation: u64,
/// Content id of `wires` (Phase 3.2). Stable across a pure pan that reuses
/// the Model-tile tessellation, so `prepare` skips re-uploading the
/// world-space wire buffer when only the camera moved. Non-tile and
/// preview/interim frames carry a fresh id each time → always re-upload.
pub(super) wire_content_id: u64,
/// Screen rectangle this viewport fills, **normalized** to the widget
/// bounds (each component in 0..1). A single full-widget view is
/// `(0, 0, 1, 1)`; tiled / floating viewports are sub-rectangles.
@ -227,9 +231,6 @@ impl shader::Primitive for Primitive {
inner.upload_images(device, queue, &vp.images[..]);
inner.upload_meshes(device, &vp.meshes[..]);
}
// Wires re-upload on every camera change because the visible
// subset shifts under frustum culling.
inner.upload_wires(device, &vp.wires[..], &vp.draw_depths);
inner.upload_face3d(
device,
&vp.face3d_wires[..],
@ -239,6 +240,17 @@ impl shader::Primitive for Primitive {
);
inner.cached_epoch = cur_key;
}
// Wire buffers are world-space, so a camera move alone doesn't
// change them — only the view_proj uniform (uploaded every frame).
// Gate the upload on the wire content id instead of the camera tick
// (Phase 3.2): a pan that reused the Model-tile tessellation keeps
// the id, skipping the vertex re-pack + GPU write. Kept independent
// of the `cur_key` block so a preview/interim wire change still
// uploads even when the camera didn't move.
if vp.wire_content_id != inner.cached_wire_id {
inner.upload_wires(device, &vp.wires[..], &vp.draw_depths);
inner.cached_wire_id = vp.wire_content_id;
}
let vproj = vp.uniforms.view_proj;
inner.compute_wire_scissors(vproj, clip_size.width, clip_size.height);
inner.compute_wipeout_scissors(vproj, clip_size.width, clip_size.height);
@ -587,22 +599,39 @@ impl Scene {
// tile's camera — culling/LOD depend on per-tile zoom, not the
// active tile's. Paper-space content viewports already had a
// per-viewport cache.
let base_arc = if let Some(tile_idx) = inst.tile_idx {
// `tile_wire_gen` is the Model-tile content id (Phase 3.2): present
// only on the tiled Model path, where a pan reuses the tessellation
// and its id so the GPU wire upload can be skipped. The other wire
// sources don't participate and force a re-upload below.
let (base_arc, tile_wire_gen) = if let Some(tile_idx) = inst.tile_idx {
let aspect = if full.height > 0.0 {
full.width / full.height
} else {
1.0
};
self.model_tile_wires_arc(tile_idx, &inst.camera, aspect, full.height)
let arc = self.model_tile_wires_arc(tile_idx, &inst.camera, aspect, full.height);
(arc, Some(self.last_model_wire_gen.get()))
} else if inst.paper_sheet {
// The sheet renders the paper block's own entities + viewport
// borders — NOT the projected viewport content (the GPU content
// viewports draw that themselves).
self.paper_sheet_wires_arc()
(self.paper_sheet_wires_arc(), None)
} else if inst.handle == acadrust::Handle::NULL {
self.entity_wires_arc()
(self.entity_wires_arc(), None)
} else {
self.model_wires_for_viewport_arc(inst.handle, full.height)
(self.model_wires_for_viewport_arc(inst.handle, full.height), None)
};
// Wire-buffer content id for the upload gate. Live preview / interim
// wires are appended below and vary frame-to-frame, so any frame
// carrying them forces a fresh upload, as do the non-tile paths.
let has_overlay = self.interim_wire.is_some() || !self.preview_wires.is_empty();
let wire_content_id = match tile_wire_gen {
Some(g) if !has_overlay => g,
_ => {
let n = self.wire_force_nonce.get().wrapping_add(1);
self.wire_force_nonce.set(n);
n | (1u64 << 63)
}
};
let (face3d_wires, other_wires) = split_face3d_wires(&base_arc, &self.document);
let all_wires = if self.interim_wire.is_none() && self.preview_wires.is_empty() {
@ -694,6 +723,7 @@ impl Scene {
hidden_line: flags.hidden_line,
geometry_epoch: self.geometry_epoch,
camera_generation: self.camera_generation,
wire_content_id,
screen_rect,
})
}