Join Ryan Kittleson for an in-depth discussion in this video Subdividing a model without losing volume, part of ZBrush: Tips & Tricks.
- This trick is kind of similar to the one in the previous video. But it's also different in some big ways. The problem that I'm addressing here is one that is shared by all my 3D software that subdivide polygons. And that is shrinkage. It's a technical term. And ZBrush is actual worse at this than other programs. Because not only do the higher subdivision levels lose volume, but the base mesh shrinks, as well. This is especially apparent on low polygon models. But it happens to all models regardless. In this video, I'll show you some ways to compensate for this shrinkage.
It's especially useful if you want to retain your low poly base mesh for animation in another program. Because if the model changes between ZBrush and another program, that can cause problems. So let's see how it works. First, let me show you what this shrinkage looks like. I'm going to make a duplicate of this model. So we can compare before and after. Let's go to the duplicate. And I'm just going to hit Control D and subdivide this a few times. I'm also going to go into solo mode so we just see one sub tool at a time.
I'm just going to go up and down between the two and you can see that the subdivided model is a little bit smaller than the original. It shrinks inwards. You can see it, especially at the shoulders and the arms. The silhouette kind of shrinks in a little bit on the subdivided version. Now here's something interesting, if I go to the one that I subdivided and I hit Shift D to go back to the original subdivision level, now let's go and compare the two. So you can see that our base mesh actually lost volume, as well.
Not just the higher subdivision levels. Okay, so let's go ahead and delete this duplicate. Okay. And I'm just going to make another duplicate so we can compare the before and after with this next round. What I want to do is save this into a macro. So, part of the macro is going to be using morph targets. And, what I want to do is in the macro, delete any existing morph targets. So, right now the model has a morph target.
But if you're working on a model that doesn't currently have a morph target what you're going to notice is that the Store MT button is active. So I just deleted the morph target. So what I want to do actually is click on Store MT to make sure that there is a morph target active. And now we can go and start recording this macro. So New Macro. Remember to ignore ZBrush's urging here and hit No instead of Yes. All right, so first thing I want to do in this macro is to delete any existing morph targets.
And now let's store a morph target. This is going to make ZBrush remember the shape of the base mesh. Now let's go ahead and subdivide once with Control D. And now I'm going to go back one subdivision level with Shift D. Now let's switch the morph target to make the shape of the lowest subdivision level the same as it was before we added that subdivision level. Now I'm going to hit D to go up one subdivision level. And let's go to Macro, and End Macro. Then let's make sure we save this in our ZBrush installation folder.
And we'll call this one Subdiv no shrink. Okay, let's go ahead and run this macro a few times. Go up to Macro. Subdiv no shrink. 'Til it's nice and smooth. And then what we can do is go ahead and compare this with the original model. So here's the original, and you can see if we go up and down, the overall volume stays the same.
So when you're using this macro it remembers the volume of the model every time you subdivide. So that there's no shrinkage. Feel free to move this macro into your main user interface. I actually like to save it to the hot key Control D so it replaces the default subdivision function. Okay, there we have it. A model that preserves the volume when it's subdivided. It also preserves more of the detail of the model without smoothing it out so much every time you subdivide.