CAD formats describe shapes mathematically — a cylinder is an axis and a radius, not an approximation made of triangles.
STEP
The main neutral CAD interchange format. Carries exact surface geometry, assembly structure and some metadata, and is readable by essentially every CAD application. When a manufacturer asks for a file, this is usually what they mean.
IGES
Older, still encountered, generally superseded by STEP. Carries surfaces but handles solids and assemblies less well.
Native formats
Each CAD application has its own, which preserves full parametric history — the sequence of operations that built the part. That history is what makes a CAD model editable by changing a dimension, and it does not survive translation to STEP.
Why this matters for 3D art
- CAD to mesh is routine. You choose a tessellation quality and get triangles. Every CAD tool exports OBJ, STL or FBX.
- Mesh to CAD is inference and rarely satisfying. Reconstructing "this is a 6mm hole" from triangles is a reverse-engineering problem, and the output is usually less editable than a native model.
Converting CAD for real-time use
A tessellated CAD model is a poor game asset directly: uniform density unrelated to visual importance, no UVs, triangle-soup topology, and often thousands of tiny separate parts reflecting the engineering assembly.
Treat it as a high-poly source. Retopologise, unwrap, bake — the same path as a sculpt or a generated mesh.
Where generation cannot help
Anything that will be manufactured to a dimension. Generated output approximates a shape; manufacturing needs an exact one. Use generation for visualisation of a design, not for the design itself.