Product · SceneReady

Decimation levels — one B-rep, five triangle budgets

A game engine's first question about an imported CAD model is how many triangles? A B-rep has no answer until export — a STEP file stores surfaces, not facets — so NativeCAD lets the chord tolerance decide: every LOD tier below is the same solid model, freshly tessellated at a coarser tolerance and written as its own GLB. Each tier is a fresh answer against the exact geometry rather than a collapse of the fine mesh.

cad_export_body { format: "glb", tolerance: 0.5, path: "prop_lod3.glb" }   // chord tolerance, mm

Or hand the kernel the budget instead of the tolerance — it walks a coarsening ladder and returns the finest mesh at or under the count, and reports the shortfall if even the coarsest mesh exceeds it, never a silent overshoot:

cad_export_body { format: "glb", maxTriangles: 500, path: "prop_far.glb" }

Compare the tiers

Loading the LOD index…

Every model, every tier

Poster shots are rendered straight from the shipped GLBs with the wireframe overlaid — on this page the mesh density is the subject. Click any tier to load it in the viewer above.

Why fresh tessellation beats mesh decimation

Coarse still shades smooth. Per-vertex normals come from the B-rep surfaces, so the 104-triangle shaft still shades like a cylinder. A decimator working on the fine mesh has only triangles to average; the exact geometry is gone.
Watertight at every tier. Each level is a full kernel tessellation of a closed solid — no collapsed slivers, no pinched holes, no shells that leak at the seams after aggressive reduction.
The budget goes where the curvature is. Planes are minimal at every tier; only curved faces spend more triangles at tighter tolerance. On the drilled bracket, LOD0 and LOD4 differ almost entirely in the five bores.
Instancing multiplies the savings. The pin array stores ONE pin mesh referenced by 28 nodes. Re-tessellating that one mesh re-LODs every placement: the drop a renderer sees is 28× the drop on the wire.
Provenance per file. Every GLB records its source document, tessellation settings and kernel version in the asset record — a level in your asset pipeline can be traced back to the tolerance that produced it.