Car Assembly Simulator

hooray! roblox doesn’t complain any more!

headless blender kinda works now, but the normals are broken in a different way?! the converter now streams in keyword data and imports it to blender via wavefront, while applying a decimate + data transfer + solidify LoD pipeline, except the solidify breaks baked normals??

small problem: Roblox really really really doesn’t like me trying to import a >200,000 tri mesh, so i had to add a decimation step to the mesher. i tried multiple open source algorithms for decimation, but none of them were able to preserve enough fidelity, and others completely broke (see the attached screenshot). plan B is to write a headless blender driver to do the decimation for me :(

yes, i’m going to use roblox

why? putting microtransactions in a menial game sounds really funny to me

no, i have absolutely zero clue about:

1. why all the shelled face normals are inside out
2. why none of my material properties carried over
3. how the heck i’m supposed to record piece offsets after the roblox importer ignored all of the explicit mesh origins

materials work now! the material type (steel, plastic, etc.) is automatically detected from the plasticity of each part because LS-DYNA doesn’t encode material names. also, i had to switch to manual gLTF generation to add the material properties and joint metadata.

however, when i was adding the joint detection, i found that inter-part constraints may constrain an arbitrary number of nodes in arbitrary locations, which makes it impossible to map the entire assembly of parts to specific screws in a way that makes sense for a game. instead, i think i’m going to use an absolute grid system for part placement, and just take the part positioning for granted

the LS-DYNA keyword convert is almost done after writing an algorithm to offset & thicken *ELEMENT_SHELL to the correct thickness! i just need to implement material and mate copying!

yay! all of the geometry exports cleanly now, and in one assembly file! to implement this, i first process each part by fixing broken geometry, triangulating quads/n-gons, and merging its 1000’s of finite elements/shells into one manifold. then, i insert the mesh into a glTF scene at the correct location, and it works!

i had this incredibly funny idea for a puzzle game: all of the parts for a car/computer/(other complex mechanical assembly) are dumped in front of the player, who must assemble [that thing] from scratch.

i searched online for high-fidelity full-assembly CAD of a car. i eventually found GMU CCSA’s public library of scanned cars (with internals!). unfortunately, all of the files use a weird ahh format called LS-DYNA that’s typically used for finite element analysis. obviously the only logical solution is to reverse engineer the file format because too bad it lacks basically any documentation :(.

so far i’ve figured out how to export individual parts, so long as the part consists exclusively of non-degenerate hexahedrons