feat(constellarium): rebuild on pixi + d3-force — Obsidian's actual mechanics - #147
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…echanics
The old Constellarium ran cosmos.gl, a GPU particle simulator with its own
shader integrator. It could show 12k points, but no parameter tuning could
make it feel like Obsidian, because the feel is not a parameter: it is
d3-force's velocity-Verlet settle plus a handful of very specific
interaction behaviours. Researched against the canonical open replica
(Quartz v4 graph.inline.ts — pixi.js + d3-force, the same stack Obsidian
itself credits) and implemented its mechanics verbatim:
charge = forceManyBody().strength(-100 * repelForce) [repel 0.5]
center = forceCenter().strength(centerForce) [0.3]
link = forceLink().distance(linkDistance) [30]
collide = forceCollide(nodeRadius)
radius = 2 + sqrt(degree)
hover → non-neighbour nodes AND links tween to α0.2 over 200ms;
hovered label pops to α1 at 1.1x over 100ms
label → α = max((k · opacityScale − 1) / 3.75, 0) — the zoom fade law
drag → alphaTarget(1) reheat on grab; fx delta divided by zoom k;
release un-pins so the node re-floats
Plus the four Obsidian force sliders (center / repel / link force / link
distance) live on the running simulation, and a text-fade slider — the
"behaves like Obsidian" ask made literal.
Deviations, each deliberate and documented inline:
- node radius capped at 14: our hub entities reach degree 500+, which no
vault sees — uncapped they render as plates
- labels materialised for the top 400 by degree + on hover, not all 5k:
Obsidian-scale vaults are hundreds of notes; faint stars' labels are
zoom-faded to zero anyway, so this is visually indistinguishable
- deep tier 12k -> 5k: d3-force is CPU; Obsidian itself slows at that
scale, and the feel matters more here than raw count. The GPU full sky
still exists at /galaxy.
Kept: manuscript chrome, tier picker, seek, folio panel, the curated
12-hue warm community palette, community-bearing seeding.
Bundle 570kB -> 360kB (cosmos + webgl-device out, pixi + d3 in).
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GobDsDKP6FE5hr747DPtcC
vicquick
enabled auto-merge (squash)
August 21, 2026 21:28
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Why cosmos.gl could never feel like Obsidian
The feel isn't a parameter. It's d3-force's velocity-Verlet settle plus a handful of very specific interaction behaviours, and cosmos.gl runs its own shader integrator. Tuning was never going to converge.
Research (stored in nobrainr, tags: research/obsidian-graph)
Obsidian core is closed, but the canonical open replica — Quartz v4
graph.inline.ts— uses pixi.js + d3-force and its mechanics are readable. Cross-checked against Obsidian's official Help (sliders, filters, groups) and the plugin ecosystem (Pixi.js WebGL mirrors the core's stack).The mechanics, implemented verbatim
forceManyBody().strength(-100 * repelForce), repel 0.5forceCenter().strength(0.3)forceLink().distance(30)+ strength sliderforceCollide(nodeRadius)2 + √degreeα = max((k·opacityScale − 1)/3.75, 0)— the exact zoom lawalphaTarget(1)reheat on grab;fx = init + Δ/k; release un-pins, node re-floatsPlus Obsidian's four force sliders live on the running sim + text-fade slider — "behaves like Obsidian" made literal.
Deliberate deviations (documented inline)
/galaxy.Kept
Manuscript chrome, tier picker, seek, folio, the curated 12-hue warm palette, community-bearing seeding.
Bundle 570kB → 360kB. Build passes.
🤖 Generated with Claude Code
https://claude.ai/code/session_01GobDsDKP6FE5hr747DPtcC