Show HN: Arxel – Constraint-driven 3D building masses in the browser

Hi HN,

I am a solo developer building Arxel (arxel.app), a web tool for architects and computational designers to explore early-stage building volumes.

I noticed that designers often spend a lot of time manually iterating on basic geometries just to see what fits within site boundaries and volume limits. I wanted to turn this into a search problem.

You input your boundary dimensions, target volume, and floor height. Under the hood, Arxel uses the Google OR-Tools CP-SAT solver to find valid configurations. It enforces rules like gravity (voxels must be supported) and connectivity, so every output is physically viable.

The solutions stream into the 3D viewport in real-time. You can then filter the results and export directly to OBJ.

I would love to hear your feedback on the solver approach or the UX. Thanks for checking it out.