Meshes are only a lossy approximation of the actual geometry, and the errors accumulate as features reference off of earlier features.
A simple example is a line tangent to an arc. The line will only be the correct distance from the center of the arc at one point (one angle) per segment.
In openscad you don't notice the problem because since it's code and you have variables and programming ways of expressing relationships, you would usually not try to derive one thing from another by geometry, instead both things would reference a common ancestor variable. But that's a technical implimentation detail that works around the problem by just not doing a thing that doesn't work. The problem is still there that a valid geometry constraint would produce invalid results.
but then the author used the source directly as noted in the Github footnote:
>I ended up directly using solvespace's solver instead of the suggested wrapper code since it didn't expose all of the features I needed. I also had to patch the solver to make it sufficiently fast for the kinds of equations I was generating by symbolically solving equations where applicable.
I do agree that historically, software aimed at building 3d models for games/animations and other digital use was usually called modeling and not cad. I'm thinking of software like 3D Studio Max back in the 90s here.
https://en.wikipedia.org/wiki/CAD/CAM
I notice though that the Wikipedia article for CAD says: "This software is used to increase the productivity of the designer, improve the quality of design, improve communications through documentation, and to create a database for manufacturing."
like I can model a table that is the right size and looks like it will not tip over for my game, but I am going to cad that table to run a stress sim and make the plans for building it for real.
though id still call the action of doing the building in the cad software "modeling"... so idk.. language is weird.
so software that lets you work accurately with measurements and real units == cad. (fusion360) software that just makes geometry == modeling. (blender)
but if you wanna go get real confused look at "plasticity" an app targeted at "modeling" but uses a cad engine and sells itself as "cad for artists" it has real scale measurements and everything too.