Perf S2: viewport culling (zoomed-in) + throttled minimap - #69
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When zoomed into a large graph, most nodes are off-screen yet still painted every frame — off-screen SVG costs the same to paint as on-screen. Add geometric viewport culling: node groups (and edges with both ends hidden) outside the viewport + margin get display:none, so they are neither laid out nor painted. Do-no-harm gating (learned by measurement): culling is skipped below scale 0.5 (the whole-graph "fit" view, where every node is on screen and a cull pass is pure overhead — an early attempt that culled unconditionally slowed zoom). When zoomed back out below the threshold, everything is revealed once. Culling is only enabled above 200 nodes. Recomputed on a throttle during sim ticks AND on every pan/zoom (the one-shot sim is usually stopped, so the zoom handler is the only thing that can reveal nodes panned back into view). Also throttle the minimap position-dict rebuild (every tick -> every 8th); it doesn't need 60 Hz and was rebuilding a full 1000-entry dict per tick. Measured (Compute Core, 1000n/1400e, HIGH), zoomed in to scale ~1.7 (982 nodes culled): zoomed-in drag FPS 1.2 -> 9 (~8x). Whole-graph fit-view drag/zoom unchanged (do-no-harm); idle still 60 (S1 preserved). The whole-graph view (scale ~0.1, all elements painted) is bound by element count, addressed next by simplified-node LOD. large-graph-profile.spec.ts now also measures a zoomed-in drag + culled count. Verified: web typecheck 0; THE GATE 5/5; hierarchy-navigation green. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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This was referenced Jun 15, 2026
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Stage 2 of the measured large-graph performance effort (follows #68)
When you zoom into a large graph, most nodes are off-screen but still painted
every frame. This adds geometric viewport culling: off-screen node groups
(and edges with both ends off-screen) get
display:none, so they're neither laidout nor painted.
Do-no-harm gating (driven by measurement)
A first attempt culled unconditionally and slowed zoom — because at the
whole-graph "fit" view (scale ~0.1) every node is on screen, so a cull pass is
pure overhead. So culling now:
zoom back out;
one-shot sim is usually stopped, so the zoom handler is what reveals nodes
panned back into view).
Also throttles the minimap position-dict rebuild (every tick → every 8th).
Result (Compute Core, 1000n/1400e, HIGH)
The whole-graph view (scale ~0.1, all 40k SVG elements painted) is bound by
element count, not culling — that's the next stage (simplified-node LOD at low
zoom), which targets the FPS you feel when looking at the entire graph.
Verification
test:smoke) 5/5hierarchy-navigationgreen (exercises the 1000-node Compute Core)large-graph-profile.spec.tsextended with a zoomed-in drag + culled-count assertion🤖 Generated with Claude Code