[reczkok]

Adds triangular patch surfaces to meshes, with subdivision separate from surface sampling

• icosphere, capsule and rounded box primitives
• tessellate into indexed geometry or sample patches directly in vertex shaders
• shared index buffer across subdivision levels, so detail can change without rebuilding buffers
• spherical interpolation helpers + an interactive patch tessellation example

Tessellation and spherical interpolation ideas yoinked from @deluksic’s de/geometry-spheres branch, shared in the original PR comment

Stacks on #2997

[github-actions]

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https://pkg.pr.new/software-mansion/TypeGPU/typegpu@b83da478cd244cca83dd5415ca70c313a5f44a19

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Bundle size comparison (import * as ... in PR vs import * as ... in target):

🟢 Decreased	➖ Unchanged	🔴 Increased	❔ Unknown
0	355	0	0

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[github-actions]

Resolution Time Benchmark

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[Copilot]

🟡 Changes recommended

Rounded-box radius handling can invert faces for thin dimensions, while fully rounded boxes retain unnecessary collapsed geometry.

2 open issues

• Clamp rounded box radius to prevent inverted face winding · New
• Omit collapsed patches when rounded box inset is zero · New

What changed in this PR

Adds triangular patch surfaces to the meshes API, separating surface sampling from subdivision. This supports both indexed geometry and direct vertex-shader evaluation.

Changes:

• Adds icosphere, capsule, and rounded-box patches with tessellated convenience constructors.
• Introduces triangle subdivision utilities, reusable index prefixes, and spherical interpolation helpers.
• Adds an interactive example and tests for topology, surface sampling, and shader resolution.

File	Description
packages/​typegpu-geometry/​tests/​patches.test.ts	Tests subdivision, watertightness, and interpolation specialization.
packages/​typegpu-geometry/​tests/​mesh.test.ts	Extends primitive and degenerate-triangle checks.
packages/​typegpu-geometry/​src/​mesh/​triangles.ts	Defines patch surfaces and subdivision utilities.
packages/​typegpu-geometry/​src/​mesh/​patchPrimitives.ts	Adds tessellated primitive constructors.
packages/​typegpu-geometry/​src/​mesh/​patches/​spherical.ts	Implements spherical interpolation helpers.
packages/​typegpu-geometry/​src/​mesh/​patches/​rounded.ts	Implements capsule and rounded-box patches.
packages/​typegpu-geometry/​src/​mesh/​patches/​index.ts	Exports patch constructors and interpolation helpers.
packages/​typegpu-geometry/​src/​mesh/​patches/​icosphere.ts	Implements icosphere patches.
packages/​typegpu-geometry/​src/​mesh/​index.ts	Exposes the new mesh APIs.
apps/​typegpu-docs/​tests/​individual-example-tests/​mesh-patches.test.ts	Checks example pipeline shader resolution.
apps/​typegpu-docs/​src/​examples/​rendering/​mesh-patches/​meta.json	Registers the example metadata.
apps/​typegpu-docs/​src/​examples/​rendering/​mesh-patches/​index.ts	Demonstrates adjustable subdivision with shared indices.
apps/​typegpu-docs/​src/​examples/​rendering/​mesh-patches/​index.html	Provides the example canvas.

_{Review effort: Balanced}

[pullfrog]

Important

roundedBox silently produces inside-out geometry when radius exceeds half the smallest box dimension, and a majority-degenerate, non-manifold mesh at exactly half. inset = halfSize - radius is never clamped or validated.

( ◦°^°◦) 🏴‍☠️

Ahoy! I plundered the diff o' PR #3014, ran the geometry tests, typecheck and linters, and keelhauled one leaky roundedBox radius that flips the hull inside-out when it be past half the smallest beam. One warnin' be posted below, savvy?

Reviewed changes

• Patch surfaces — adds icosphere, capsule and roundedBox as shader-evaluated PatchSurface objects under src/mesh/patches/, with spherical interpolation helpers (linear, uniformArea, arc, warp).
• Triangle tessellation — triangles.ts adds the CPU helpers triangleVertexCount/triangleIndexCount/triangleIndices and the GPU helpers triangleBarycentrics/triangleIndexAt, plus tessellate mapping a linear vertex index onto a triangular grid.
• Shared index buffer — triangleIndexAt is segment-independent, so one max-segment index buffer works as a prefix at every lower subdivision; the new docs example drives detail from a single buffer while the vertex shader recomputes barycentrics.
• Patch primitives + example — patchPrimitives.ts tessellates the three shapes with a segments option, plus a new mesh-patches docs example and jsdom example test.

I verified the geometry tests (44 passing), typecheck, lint and formatting locally, and independently checked that the index-prefix property holds for every segment value in [1..32] and that capsule/icosphere stay watertight and correctly wound across the probed parameter ranges. The only issue found is the unclamped radius below.

[pullfrog]

✅ No new issues found.

( ◦°^°◦) 🏴‍☠️

Ahoy! I boarded the new commit on PR #3014 and found the leak I'd flagged last voyage already plugged — the roundedBox radius be clamped to half the smallest beam, so no more inside-out hulls. Batten down the tests and let her sail.

Reviewed changes

• Clamped the rounded-box radius — roundedBox now resolves radius as Math.min(maxRadius, halfSize.x, halfSize.y, halfSize.z) (patches/rounded.ts:92) and documents it as "Clamped to half of the smallest dimension". This removes the negative inset that previously mirrored face/edge patches and wound ~55% of triangles inside-out once radius exceeded half the smallest dimension.
• Added a thin-box winding case — mesh.test.ts gains ['thin rounded box', meshes.roundedBox({ height: 0.05 })], exercising the newly clamped path where inset reaches zero on the smallest axis.

I re-ran the geometry suite (45 passing) and package typecheck, and independently probed five configurations (radius well above min/2, exactly min/2, thin boxes, and a normal case): none produce inside-out triangles anymore. The residual trade-off — collapsing to exactly min/2 leaves zero-area face/edge patches on the smallest axis (e.g. radius: 0.5 on a unit cube yields 576/704 degenerate triangles) — is wasted geometry rather than a rendering defect, and matches the clamp semantics the author chose. Prior review's inline thread is resolved on GitHub.

  ^{｜ Fix it ➔ ｜ View workflow run ｜ Using deepseek-v4.1-flash (free via Pullfrog for OSS) ｜ 𝕏}