🔺 Meshing

Automatic Delaunay triangulation with Ruppert refinement — fast, high-quality, running entirely in your browser via WebAssembly.

The spade Mesher

ThermX uses spade, a Constrained Delaunay Triangulation (CDT) engine written in Rust and compiled to WebAssembly (WASM). The spade WASM binary is only 185 KB — small enough to ship inline — and runs at near-native speed in both the browser and desktop app.

The meshing algorithm is based on Ruppert's refinement, which iteratively improves mesh quality by inserting new Steiner points until all triangles meet the user-specified angle and area constraints.

Generating a Mesh

Complete your geometry (all regions drawn, no overlaps)
Assign materials and boundary conditions
Open the Mesh tab in the right panel
Adjust quality parameters if needed (defaults work well for most models)
Click Generate Mesh

The mesh is generated in a background Web Worker so the UI remains responsive. For typical building component cross-sections, meshing takes under one second.

Quality Parameters

Min edge length

0.5 – 50 mm

Lower bound on triangle edge length. Prevents over-refinement in thin regions. Default: 0.5 mm.

Max edge length

0.5 – 50 mm

Upper bound. Larger values produce coarser meshes. Default: 10 mm. Both sliders use a logarithmic scale.

Min angle

0 – 34°

Minimum interior angle for any triangle. Higher values improve numerical quality but increase element count. Default: 20°.

Max area

Any (mm²)

Maximum area per triangle. Leave blank to disable. Useful for ensuring fine resolution in large homogeneous regions.

Best Practice

Start with defaults. If results show large temperature gradients in a region, reduce max edge length there or set a max area constraint and remesh. For thin insulation layers, ensure min edge is smaller than the layer thickness.

Dual-Slider Controls

The min/max edge length sliders are linked: the minimum can never exceed the maximum. Both sliders use a logarithmic scale so that fine control is available at small values (below 2 mm) while still allowing coarse values up to 50 mm.

Real-Time Mesh Preview

After meshing, the canvas shows the triangulation overlaid on your geometry. Triangles are color-coded by quality:

Green — High-quality triangles (angles near 60°)
Yellow — Acceptable quality
Red — Poor quality (sharp angles); consider tightening the min angle constraint

Hover over any triangle to see its area, minimum angle, and element index.

Mesh Statistics

After generation, the Mesh panel shows:

Total number of triangles
Total number of nodes
Minimum and maximum triangle angles
Generation time

Technical Details

Component	Details
Algorithm	Constrained Delaunay + Ruppert's Refinement
Implementation	spade (Rust crate)
Runtime	WebAssembly (WASM), 185 KB binary
Threading	Runs in a Web Worker (non-blocking)
Constraints	All geometry edges are preserved as constrained edges
Material boundaries	Automatically preserved — no triangle spans multiple materials

Common Issues

Meshing fails or hangs

This usually means geometry has overlapping regions or extremely short edges (degenerate geometry). Check for overlaps using Check Geometry and ensure no vertices are placed closer together than the min edge length.

Too many elements, slow solve

Increase the max edge length or the max area. For a quick check, use a coarse mesh; for final results, refine.

Poor quality near thin layers

Reduce the min edge length below the layer thickness. Alternatively, increase the min angle to force more equilateral triangles in those regions.