Now, that’s just one object. It has a lot of parts that are common for me in my NURB to polygon workflow. But some more specialized things might be in order to talk about.

First up is trimmed surfaces. Due to the way MoI deals with them, they usually result in odd boundary edges. Especially if the trim is an interior trim. First let’s tackle them on planer surfaces. If you take, say, a round cap and punch holes in it, the default meshing surface looks like utter crap. This is the usual mess of random connection lines you get from Booleans in polygon modelers, actually.



Now, taking the idea from before about using trims to force edges where we want them, we can make something like this regular bolt pattern work fine just by putting a slice right down the middle of each one.



This is one of the few times I’d take a circle down to a square. It will subdivide perfectly round, the geometry is already pretty heavy, and these holes would NEVER be actual geometry on a game model; they’d just be normal and/or alpha mapped on. To clean this up, I needed to just connect some points and add some loops.



I’m holding those edges via edge weights (something I’ve come to love for holding machined edges in sub-d models without increasing the mesh density). Now, the display smoothing may look a bit rough, but it renders as intended, and if I actually physically SDS divide it also looks fine.

Now, doing trims on another curved surface has the same ideas. Add in trims to control things and then tweak the mesh settings. Take this round hole through a cylinder.



To properly mesh this, you have to actually understand a bit about putting holes in subdivision objects. The general idea is to have as few sides as you can get away with and to keep as many quads as possible. For this, the shape maintains fine with the cut circle being only eight sided. But, at that division, the outer cylinder is also at the same eight sides. This causes the object to not have enough edges to maintain shape.



To make this work, there’s two ways. The first is to toy with the “divide larger” option until you have the sides you want. For something this simple, it works. But, if this method fails, the other option is to mesh the two cylinder parts separately and then sew them up in a polygon modeler.



One thing to keep in mind, though, is that at this low of a resolution, there will likely be some warping near the drilled hole; this is just the nature of subdivision surfaces and the only way to get around it is to add more damn edge loops.



The one on the left is the model out of MoI, with edge weighting and a couple edges added. The one on the left is the result of running a Smooth subdivision on it. You could also compensate for the warping by moving the lip of the cut inward, but that creates odd problems too.