Learn about the various ways that you can automatically create polygroups in ZBrush that are customized for the kind of work you need to do.
- As I'm sure you know by now, polygroups are a great way to keep a model organized. Zbrush is pretty good about creating polygroups automatically while modeling. But sometimes, those polygroups aren't helpful or they're missing. In this video, we'll look at some ways of quickly generating new polygroups. Okay, so let's take a look at some pieces of this model. I'm going to zoom in here and alt click on the shirt to make that the active subtool. Then, I'll hit shift F to turn on wireframe. Nope. Looks like that didn't quite take when I alt clicked on the shirt.
Let me try that one more time. Okay, looks good. So, you can see that this shirt is one single polygroup. But we might want to control things for the edge of the shirt separately from the inside of the shirt or the outside. So, let's see how we can automatically create some polygroups for this. So, let's scroll down to our polygroups pallet. One of the most useful ones in here is Groups By Normals. And what this means is that any parts that are kind of mostly flat with each other will get grouped into one group, and anywhere there's a sharp angle, it'll create a new polygroup.
So, let's just try Groups By Normals with the default settings. Okay, this is actually pretty good. I'm going to go into solo mode so we can see this without any other models in the way. So, you can see what this did is it created a polygroup for the outside, one for the edge, and one for that little strip of polygons that's on the inside of the shirt. Now, what you can do is change the angle, here. So, if you set this lower, what it'll do is actually be more sensitive. So, here you can see that this group of polygons right here at the edge, there was kind of a sharper angle right here, which means that that splits that off into two polygroups.
And actually, another change of polygroup up here because of that angle. So, you might need to play with this a little bit to get this right. So, for example, I probably want to keep one polygroup in this entire loop all the way around. So, you want to find the angle that's right for that. Now, if you set it too high, what you'll probably find is that things get combined that probably shouldn't be. So, you can see this edge polyloop right here is getting combined in the same polygroup as the shirt because those angles are soft enough to where, when it's set to 72 degrees, it's combining it.
So, you just want to find that happy medium where you get the polygroups you want, but not too many. Another way to control polygroups that I like a lot is called Group Front. And so, what you can do with this is just click Group Front, and any polygons that are facing the camera will get grouped. So, you can see all of the others are left alone. So, you're going to come around to the back side and Group Front here, and now we've got mostly two polygroups and some that are kind of, like, right in the middle; not really facing forward or backwards will sometimes get left like that.
Actually, with perspective mode turned off, I think we can finally catch everything. Let's try this. Group Front again. And Group Front on the backside. Okay, yeah, because perspective was kind of distorting how the polygons are facing the camera, which made it so that some of them weren't quite caught from either view. You can also change the angle on this. So, this, by default, is set to 90 degree angle, so that means that any polygon that's even remotely facing the front of the camera will get included.
But we can set this lower. So, if we come around, snap to the front view, set that to something lower like 18, now click Group Front, only polygons that are facing the camera with a range of tolerance of 18 degrees away from the camera will be grouped together. So, that's just another way to isolate different polygons by groups. And you could actually bring that angle higher than 90 so that when we click it again, it groups everything; even polygons that are facing away from the camera, as long as they are within 152 degrees, for example.
Now, there's one other setting here that's kind of interesting. It's Group Visible. And if we click this with the default settings, it basically makes everything that's visible one solid polygroup. However, there's some interesting things we can do with this. We can change the coverage, and it's sort of a randomizer. So, let's say we set it to .5, so that means that 50% of the polygons will be affected by this, and it's completely random. So, if we click this again, you can see that we've got just random polygroups.
Now, why would you want random polygroups? Well, it might come in handy if you want to, let's say, create some sort of natural looking terrain. And you could insert nanomeshes based on polygroups. So, if you want the nanomeshes to be distributed in kind of a random way, this can help you create the polygroups necessary to do that. Now, there's actually something else that's kind of interesting with this is it can cluster them together. So, if we have this set to a higher number, these polygroups that will be created at random will be kind of clustered together.
Now, if we set it lower, it'll be more truly scattered random. So, you can play around with that to get the effect that you want. If you keep clicking this over and over again, you'll actually generate lots of different polygroups, and they'll all be pretty random. So, you could scatter hair or nanomeshes on the surface based by polygroup and have a pretty random organic result. Finally, I want to look at Merge Stray Groups. And this is useful a lot of times when you run the Groups By Normals.
And for the most part, it gives you the result you want, but there's a few polygons here and there that just get colored their own polygroup, and you want to make sure it's more unified; you can do Merge Stray Groups. And so, what this does is it finds little bits of polygroup that are just one, or two, or maybe three polygons that are one polygroup that are kind of isolated from everything else, and it combines them with the nearest dominant polygroup. Okay, so it can clearly take some trial and error, but these automatic polygrouping techniques can really save time when a model is very complex, and you want to be able to isolate various parts of it quickly.
Skill Level Intermediate
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