perf(render): split the wire arena into regular + mesh-edge batches

The single-batch arena required a set with no mesh/solid edges, so any drawing
with a 3D solid or mesh (this one: 1693 mesh-edge wires of 12200) disqualified the
WHOLE set — every edit fell back to build_wire_buffers re-uploading ~265 MB
(4.4M instances), stalling ~1s per edit on a shared-memory GPU.

Split the resident set into a regular-2D arena and a mesh-edge arena (the wires
that need the draw loops mesh-edge skip/black treatment), one WireArena each,
passed as &[&WireModel] subsets (no clone). Both patch incrementally; the mesh
arena carries is_3d_mesh_edge so the existing draw loop handles it. A changed
handle absent from an arenas subset is a no-op for it, so each edit touches only
the batch it belongs to. Result: the wire block drops from ~300ms + a 265 MB GPU
upload to ~2ms.

Two correctness points folded in from adversarial review:
- mesh-edge wires are stamped draw_depth 0 (matching WireGpu::from_run) so their
  hidden back edges dont peek through the shaded fill; the mesh arena also always
  bails on append (all its wires share depth 0, so relocation would reorder
  coincident edges).
- buffers are capped at wgpus 256 MB limit — a batch larger than one buffer
  returns None so the caller chunks it via the batched path (fixes a create_buffer
  panic on the 355 MB regular batch).

Still behind OCS_WIRE_GPU_PATCH (default off). OCS_PERF prints the per-edit wire
timing + outcome.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/scene/pipeline/mod.rs

@@ -154,7 +154,12 @@ pub struct Pipeline {
     /// edit patches one entity's slab in place instead of rebuilding every wire.
     #[cfg(not(target_arch = "wasm32"))]
     pub(crate) wire_arena: Option<wire_arena::WireArena>,
-    /// The Model content id `wire_arena` currently mirrors (`u64::MAX` = none).
+    /// Second arena for the mesh/solid EDGE wires (drawn with the mesh-edge skip /
+    /// black treatment); the resident set is split into this + `wire_arena` so
+    /// both patch incrementally. Shares `wire_arena_id`.
+    #[cfg(not(target_arch = "wasm32"))]
+    pub(crate) wire_arena_mesh: Option<wire_arena::WireArena>,
+    /// The Model content id both arenas currently mirror (`u64::MAX` = none).
     #[cfg(not(target_arch = "wasm32"))]
     pub(crate) wire_arena_id: u64,
     /// Pixel scissor rects [x, y, w, h] for viewport-clipped wires. Recomputed each frame.
@@ -1320,6 +1325,8 @@ impl Pipeline {
             #[cfg(not(target_arch = "wasm32"))]
             wire_arena: None,
             #[cfg(not(target_arch = "wasm32"))]
+            wire_arena_mesh: None,
+            #[cfg(not(target_arch = "wasm32"))]
             wire_arena_id: u64::MAX,
             wire_pixel_scissors: vec![],
             gpu_selected_wires: vec![],

src/scene/pipeline/wire_arena.rs

@@ -50,6 +50,12 @@ const HEADROOM_NUM: u64 = 3;
 const HEADROOM_DEN: u64 = 2;
 const MIN_INST_CAP: u64 = 4096;
 const MIN_CONST_CAP: u64 = 1024;
+/// wgpu caps a single buffer at 256 MB. An arena keeps ONE instance buffer per
+/// batch, so a batch whose instances exceed this can't be an arena — build
+/// returns None and the caller falls back to the chunked batched path. The
+/// buffer (with headroom) is also clamped here so it never exceeds the limit.
+const MAX_INSTANCES: u64 = 268_435_456 / std::mem::size_of::<WireInstance>() as u64;
+const MAX_CONSTS: u64 = 268_435_456 / std::mem::size_of::<WireConst>() as u64;
 
 struct Slab {
     inst_off: u32,
@@ -73,18 +79,29 @@ pub struct WireArena {
     /// Tombstoned instances (blanked, not reclaimed) — past half the tail a patch
     /// bails so the caller compacts with a full rebuild.
     tombstoned: u32,
+    /// Whether this arena's wires are 3D mesh/solid edges (`is_3d_mesh_edge` on
+    /// the draw batch): the draw loop hides them in clean-shaded modes and draws
+    /// them black in filled-with-edges modes. The regular and mesh-edge subsets
+    /// of the resident set each get their own arena so both patch incrementally.
+    mesh_edge: bool,
 }
 
 fn handle_of(w: &WireModel) -> Option<Handle> {
     crate::scene::Scene::handle_from_wire_name(&w.name)
 }
 
-/// True if the whole set is arena-eligible: a single batch that draws with no
-/// viewport scissor — no mesh/solid fill and no per-wire scissor.
+/// True if the set can use the arena: no per-wire scissor (paper viewports). Mesh
+/// fills no longer disqualify it — the render layer splits the set into a regular
+/// and a mesh-edge subset, one arena each.
 pub fn is_arena_eligible(wires: &[WireModel]) -> bool {
-    wires
-        .iter()
-        .all(|w| w.fill_tris.is_empty() && w.vp_scissor.is_none())
+    wires.iter().all(|w| w.vp_scissor.is_none())
+}
+
+/// True when `w`'s edge segments belong to a mesh/solid whose fill is drawn in a
+/// separate pass — such wires need the draw loop's mesh-edge treatment, so they
+/// go in their own arena. `mesh_names` are the entities that emit a fill.
+pub fn is_mesh_edge(w: &WireModel, mesh_names: &rustc_hash::FxHashSet<u64>) -> bool {
+    !w.points.is_empty() && handle_of(w).map_or(false, |h| mesh_names.contains(&h.value()))
 }
 
 /// True when appending a new entity at the tail could change the image, so the
@@ -95,7 +112,7 @@ pub fn is_arena_eligible(wires: &[WireModel]) -> bool {
 ///     Surface) are excluded from `draw_depth_map`, so their fallback edge wires
 ///     get draw_depth 0.0. Two coincident opaque such wires share a z-bias and
 ///     resolve by submission order, which a tail relocation would flip.
-fn append_unsafe(wires: &[WireModel], depth_map: &FxHashMap<u64, f32>) -> bool {
+fn append_unsafe(wires: &[&WireModel], depth_map: &FxHashMap<u64, f32>) -> bool {
     wires.iter().any(|w| {
         w.color[3] < 0.999
             || handle_of(w).map_or(true, |h| !depth_map.contains_key(&h.value()))
@@ -116,13 +133,13 @@ pub fn build_handle_index(wires: &[WireModel]) -> std::sync::Arc<FxHashMap<u64,
 }
 
 /// Group `wires` (draw-order sorted, entity-contiguous) into per-handle ranges.
-fn handle_ranges(wires: &[WireModel]) -> Option<Vec<(Handle, usize, usize)>> {
+fn handle_ranges(wires: &[&WireModel]) -> Option<Vec<(Handle, usize, usize)>> {
     let mut out: Vec<(Handle, usize, usize)> = Vec::new();
     let mut i = 0;
     while i < wires.len() {
-        let h = handle_of(&wires[i])?;
+        let h = handle_of(wires[i])?;
         let mut j = i + 1;
-        while j < wires.len() && handle_of(&wires[j]) == Some(h) {
+        while j < wires.len() && handle_of(wires[j]) == Some(h) {
             j += 1;
         }
         out.push((h, i, j));
@@ -189,13 +206,11 @@ impl WireArena {
     pub fn build(
         device: &wgpu::Device,
         queue: &wgpu::Queue,
-        wires: &[WireModel],
+        wires: &[&WireModel],
         depth_map: &FxHashMap<u64, f32>,
         const_bgl: &wgpu::BindGroupLayout,
+        mesh_edge: bool,
     ) -> Option<Self> {
-        if !is_arena_eligible(wires) {
-            return None;
-        }
         let ranges = handle_ranges(wires)?;
 
         // const slot 0 = blank tombstone target.
@@ -205,9 +220,12 @@ impl WireArena {
         for (h, i, j) in ranges {
             let inst_off = instances.len() as u32;
             let const_off = consts_cpu.len() as u32;
-            for w in &wires[i..j] {
+            for &w in &wires[i..j] {
                 let wire_id = consts_cpu.len() as u32;
-                let dd = wire_draw_depth(w, depth_map);
+                // 3D mesh outline edges are occluded by true depth and must NOT
+                // take the draw-order z-bias (or hidden back edges peek through
+                // the shaded fill) — matching WireGpu::from_run.
+                let dd = if mesh_edge { 0.0 } else { wire_draw_depth(w, depth_map) };
                 let (mut insts, cst) = emit_wire_native(w, wire_id, w.color, dd);
                 instances.append(&mut insts);
                 consts_cpu.push(cst);
@@ -225,9 +243,17 @@ impl WireArena {
 
         let inst_tail = instances.len() as u32;
         let const_tail = consts_cpu.len() as u32;
-        let inst_cap = ((inst_tail as u64 * HEADROOM_NUM / HEADROOM_DEN).max(MIN_INST_CAP)) as u32;
-        let const_cap =
-            ((const_tail as u64 * HEADROOM_NUM / HEADROOM_DEN).max(MIN_CONST_CAP)) as u32;
+        // A batch bigger than one buffer can't be an arena — let the caller chunk
+        // it via the batched path.
+        if inst_tail as u64 > MAX_INSTANCES || const_tail as u64 > MAX_CONSTS {
+            return None;
+        }
+        let inst_cap = ((inst_tail as u64 * HEADROOM_NUM / HEADROOM_DEN)
+            .max(MIN_INST_CAP)
+            .min(MAX_INSTANCES)) as u32;
+        let const_cap = ((const_tail as u64 * HEADROOM_NUM / HEADROOM_DEN)
+            .max(MIN_CONST_CAP)
+            .min(MAX_CONSTS)) as u32;
         let inst_buf = alloc_inst(device, inst_cap as u64);
         let const_buf = alloc_const(device, const_cap as u64);
         if inst_tail > 0 {
@@ -247,6 +273,7 @@ impl WireArena {
             consts_cpu,
             slabs,
             tombstoned: 0,
+            mesh_edge,
         })
     }
 
@@ -265,12 +292,9 @@ impl WireArena {
         &mut self,
         queue: &wgpu::Queue,
         changes: &[(Handle, ChangeKind)],
-        wires: &[WireModel],
+        wires: &[&WireModel],
         depth_map: &FxHashMap<u64, f32>,
     ) -> bool {
-        if !is_arena_eligible(wires) {
-            return false;
-        }
         let Some(ranges) = handle_ranges(wires) else {
             return false;
         };
@@ -282,7 +306,9 @@ impl WireArena {
         for &(h, kind) in changes {
             let new_range = range_of.get(&h).copied();
 
-            // Removed / now-hidden ⇒ tombstone the slab.
+            // Removed / now-hidden ⇒ tombstone the slab. A handle not in THIS
+            // arena's subset (it belongs to the other batch) simply isn't in its
+            // slabs, so this is a no-op for it.
             if matches!(kind, ChangeKind::Removed) || new_range.is_none() {
                 if let Some(slab) = self.slabs.remove(&h) {
                     let blanks = vec![blank_instance(); slab.inst_len as usize];
@@ -298,9 +324,9 @@ impl WireArena {
             // Emit into fresh, run-local const slots (patched to absolute below).
             let mut insts: Vec<WireInstance> = Vec::new();
             let mut csts: Vec<WireConst> = Vec::new();
-            for w in run {
+            for &w in run {
                 let wire_id = csts.len() as u32;
-                let dd = wire_draw_depth(w, depth_map);
+                let dd = if self.mesh_edge { 0.0 } else { wire_draw_depth(w, depth_map) };
                 let (mut wi, c) = emit_wire_native(w, wire_id, w.color, dd);
                 insts.append(&mut wi);
                 csts.push(c);
@@ -339,9 +365,11 @@ impl WireArena {
             }
 
             // Layout changed ⇒ append at the tail. Unsafe to relocate when the set
-            // resolves overlap by submission order (transparency, or a wire with
-            // no draw-order depth); fall back to a full rebuild instead.
-            if append_unsafe {
+            // resolves overlap by submission order: transparency, a wire with no
+            // draw-order depth, or the mesh-edge arena (all its wires are forced
+            // to depth 0, so coincident edges resolve by submission order). Fall
+            // back to a full rebuild instead.
+            if append_unsafe || self.mesh_edge {
                 return false;
             }
             if self.inst_tail + inst_len > self.inst_cap
@@ -383,7 +411,13 @@ impl WireArena {
             // depth map and re-upload the whole (small) const buffer; the instance
             // buffer is untouched.
             for (h, slab) in &self.slabs {
-                let dd = depth_map.get(&h.value()).copied().unwrap_or(0.0);
+                // Mesh-edge wires keep depth 0 (no draw-order bias); regular wires
+                // take the re-normalised map value.
+                let dd = if self.mesh_edge {
+                    0.0
+                } else {
+                    depth_map.get(&h.value()).copied().unwrap_or(0.0)
+                };
                 for k in 0..slab.const_len {
                     self.consts_cpu[(slab.const_off + k) as usize].draw_depth = dd;
                 }
@@ -406,7 +440,7 @@ impl WireArena {
             instance_buffer: self.inst_buf.clone(),
             instance_count: self.inst_tail,
             vp_scissor: None,
-            is_3d_mesh_edge: false,
+            is_3d_mesh_edge: self.mesh_edge,
             const_bind_group: Some(self.const_bind_group.clone()),
         }]
     }

src/scene/view/render.rs

@@ -369,38 +369,81 @@ impl shader::Primitive for Primitive {
                 // 2D/3D sets fall through to the shared batched path below.
                 let mut arena_served = false;
                 #[cfg(not(target_arch = "wasm32"))]
+                let _perf = std::env::var_os("OCS_PERF").is_some();
+                #[cfg(not(target_arch = "wasm32"))]
+                let _t0 = std::time::Instant::now();
+                #[cfg(not(target_arch = "wasm32"))]
+                let mut _patched = false;
+                #[cfg(not(target_arch = "wasm32"))]
                 if crate::scene::wire_gpu_patch_enabled()
                     && inner.wire_const_bgl.is_some()
                     && crate::scene::pipeline::wire_arena::is_arena_eligible(&vp.wires)
                 {
-                    use crate::scene::pipeline::wire_arena;
-                    // In-place patch from the base the GPU holds, else rebuild.
-                    let patched = if let (Some(arena), Some((base, changes))) =
-                        (inner.wire_arena.as_mut(), vp.wire_patch.as_ref())
-                    {
-                        inner.wire_arena_id == *base
-                            && !changes.is_empty()
-                            && arena.patch(queue, changes, &vp.wires[..], &vp.draw_depths)
-                    } else {
-                        false
-                    };
-                    if !patched {
-                        let bgl = inner.wire_const_bgl.as_ref().unwrap();
-                        inner.wire_arena = wire_arena::WireArena::build(
-                            device,
-                            queue,
-                            &vp.wires[..],
-                            &vp.draw_depths,
-                            bgl,
-                        );
+                    use crate::scene::pipeline::wire_arena::{self, WireArena};
+                    // Split the resident set into the regular 2D wires and the
+                    // mesh/solid EDGE wires (which need the mesh-edge draw
+                    // treatment), one arena each, so both patch incrementally.
+                    // Fill-only wires (no segments) are drawn in the face3d pass,
+                    // not here, so they go in neither.
+                    let mesh_names: rustc_hash::FxHashSet<u64> = vp
+                        .wires
+                        .iter()
+                        .filter(|w| !w.fill_tris.is_empty() && !w.fill_tris_low.is_empty())
+                        .filter_map(|w| w.name.parse::<u64>().ok())
+                        .collect();
+                    let regular: Vec<&crate::scene::WireModel> = vp
+                        .wires
+                        .iter()
+                        .filter(|w| {
+                            !w.points.is_empty() && !wire_arena::is_mesh_edge(w, &mesh_names)
+                        })
+                        .collect();
+                    let mesh: Vec<&crate::scene::WireModel> = vp
+                        .wires
+                        .iter()
+                        .filter(|w| wire_arena::is_mesh_edge(w, &mesh_names))
+                        .collect();
+                    let bgl = inner.wire_const_bgl.as_ref().unwrap();
+                    let base_ok = vp
+                        .wire_patch
+                        .as_ref()
+                        .map_or(false, |(base, changes)| {
+                            inner.wire_arena_id == *base && !changes.is_empty()
+                        });
+                    let changes = vp.wire_patch.as_ref().map(|(_, c)| c);
+
+                    // Each batch: patch from the shared base if possible, else
+                    // rebuild just that batch. They advance together.
+                    let reg_ok = base_ok
+                        && inner.wire_arena.as_mut().map_or(false, |a| {
+                            a.patch(queue, changes.unwrap(), &regular, &vp.draw_depths)
+                        });
+                    if !reg_ok {
+                        inner.wire_arena =
+                            WireArena::build(device, queue, &regular, &vp.draw_depths, bgl, false);
                     }
-                    if let Some(arena) = inner.wire_arena.as_ref() {
-                        inner.gpu_wires = std::sync::Arc::new(arena.wire_gpus());
-                        inner.wire_handle_index =
-                            wire_arena::build_handle_index(&vp.wires[..]);
+                    let mesh_ok = base_ok
+                        && inner.wire_arena_mesh.as_mut().map_or(false, |a| {
+                            a.patch(queue, changes.unwrap(), &mesh, &vp.draw_depths)
+                        });
+                    if !mesh_ok {
+                        inner.wire_arena_mesh =
+                            WireArena::build(device, queue, &mesh, &vp.draw_depths, bgl, true);
+                    }
+                    _patched = reg_ok && mesh_ok;
+
+                    if let (Some(reg), Some(me)) =
+                        (inner.wire_arena.as_ref(), inner.wire_arena_mesh.as_ref())
+                    {
+                        let mut gpus = reg.wire_gpus();
+                        gpus.extend(me.wire_gpus());
+                        inner.gpu_wires = std::sync::Arc::new(gpus);
+                        inner.wire_handle_index = wire_arena::build_handle_index(&vp.wires[..]);
                         inner.wire_arena_id = vp.wire_content_id;
                         arena_served = true;
                     } else {
+                        inner.wire_arena = None;
+                        inner.wire_arena_mesh = None;
                         inner.wire_arena_id = u64::MAX;
                     }
                 }
@@ -436,6 +479,24 @@ impl shader::Primitive for Primitive {
                 inner.wire_handle_index = built.1;
                 } // end !arena_served
                 inner.cached_wire_id = vp.wire_content_id;
+                #[cfg(not(target_arch = "wasm32"))]
+                if _perf {
+                    let gi: u32 = inner.gpu_wires.iter().map(|w| w.instance_count).sum();
+                    let outcome = if !arena_served {
+                        "shared-fullupload"
+                    } else if _patched {
+                        "arena-patch"
+                    } else {
+                        "arena-build"
+                    };
+                    eprintln!(
+                        "[perf] wire {:>7.1}ms  {:<18} wires={} gpu_instances={}",
+                        _t0.elapsed().as_secs_f64() * 1000.0,
+                        outcome,
+                        vp.wires.len(),
+                        gi,
+                    );
+                }
             }
             // Selection xray overlay — rebuilt when the selection changes or the
             // underlying wires changed. A pick bumps only selection_generation,