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Modelling Digital Eyeglasses
🕑 Added 2020-02-12 10:58:15 +0000 UTCSo I recently needed a decent pair of glasses for Jessica. The old set I was using was just some random model I'd downloaded from the internet, and while it kinda worked, I wasn't a fan of the proportions in general. I always intended on modeling up my own set of glasses prior to completing Jessica's character, but I never realized what sort of rabbit hole I was about to tumble down.
As it turns out, modelling glasses is hard.
The primary issue is that you're essentially dealing with three separate concepts that- when combined together- can quickly become extremely complicated:
- The overall style of the frames and associated parts
- The bends and curves required to turn those into an actual pair of glasses
- Modifications to the finalized shape required to fit the glasses to a character's head
At first, all three of these might seem to be interlinked. If you're modelling a pair of glasses, then they should probably look like a pair of glasses, otherwise what's the point? The problem with this is that trying to consider all three things at once quickly becomes overwhelming, especially if you want to try and keep all the curvature as uniform as possible across the entire model.
So what's the alternative?
Simple- model the glasses totally flat, with zero curvature anywhere (even on the lenses). This accelerates the modeling process considerably, and allows one to generate clean topology without having to worry about arbitrary curves bending everything around arbitrary axis. Once that has been done and the model has been UV unwrapped, bring the entire thing into any application that can apply arbitrary deformation to a polygon mesh, and literally bend the glasses into shape.
This technique has the added benefit of also allowing one to customize the glass fit to any character without having to remodel any of the geometry. Because the "style" of the glasses has effectively been decoupled from the "fit" of the glasses, there is no need to worry about any of that until you actually need to fit the frames to a humanoid head. The only thing that really needs to be considered is the horizontal width of the frame itself and the length of the arms, but since both exist as flat geometry prior to fitting it's super simple to change either of those without messing up all the curvatures and bends.
PS: While this doesn't technically accommodate for the difference in curvature of the lens surfaces, the proper magnification effect can still be achieved in 3D by simply assigning two glass-like materials with varying IORs to either side of the lens geometry, which will recreate the exact same zoom effect as seen through most IRL optics- but without actually having to calculate and model the lens curvature by hand (even I'm not crazy enough to attempt that).
