Many people have asked how to get really clean texture transfers when working with Projection Master. By this I mean crisp, sharp edges that remain once the model has been picked up again from the canvas. The truth is that getting great results like this is a simple matter of understanding what is really happening at the fundamental level when you work with Projection Master.
This mini-tutorial will take the mystery out of the process, while also providing an easy way to deal with those situations when you find yourself guessing. No more trial and error! These steps will give you great results every time.
This tutorial also supplements my Precision Texturing Tutorial which I wrote last year. That tutorial explained ways to paint crisp edges on the canvas. This tutorial goes a step farther and teaches how to ensure that those edges will transfer cleanly to your texture.
So here goes:
Let’s begin by looking at what is happening when you use Projection Master. I’m not going to go into the technical aspects of what features it automates or any of that stuff. Instead, I’m going to discuss the topology of it. For those of you who are scratching your heads at this point, let’s just say that Topology is the mathematics of surfaces. Your texture is nothing more than a flat plane that is getting wrapped onto the surface of your model. Of course, if you’ve ever tried to peel an orange into a single piece and then flatten it out onto the table top, you know that the 3D to 2D unwrapping process doesn’t work too well. There have to be breaks and/or distortions in order to get a complete unwrapping.
Projection Master takes as much of the topology (math) out of the picture as possible. The basic idea is that you paint what you want to see, and then ZBrush handles the process of applying all the math to make what you’ve just painted in 3D fit correctly onto the 2D texture map.
In order to make this work, ZBrush has to take a look at the pixols that you’ve painted on the canvas and then calculate how best to make that detail fit as pixels when projected onto the texture. “Projection” really is the perfect term for this, too. You have no doubt watched a movie in the theater at some point where the projector was out of focus until somebody complained and they fixed it. Modern movie projectors have a lot of great features to try and ensure a clean focus, but sometimes you still need human intervention. The same actually holds true for ZBrush, which has some really sophisticated routines to try and ensure an “in focus” projection when you pick the model up from the canvas. No matter how good those routines are, there are still some things that you can do to help ZBrush out. And that’s what this tutorial will help you do.
ZBrush’s projection “focus” is based upon canvas pixols vs. texture pixels. If you have too many of one relative to the other, the result will be an out of focus, poor quality projection. To illustrate, I’m going to use Hiroshi’s fun little model from this thread, onto which we’ll be projecting the Pixologic logo.
For each use of Proejection Master, the only difference is the scale at which the model is being dropped to the canvas. Each of these gives us a different ratio of pixols-to-pixels, which gives different results when the model is picked up again. (Note: The ratios mentioned in the text beneath each illustration are approximate.)
In this first example, we’ve zoomed way in on the chest (left view). As a result, the logo takes up a LOT of canvas pixols – about 800 pixols across. On the other hand, the texture that the logo will be projected onto is only 2048x2048 in size. Relatively few of those are assigned to the chest. The result is that we have a large number of pixols being projected onto a relatively small number of texture pixels. Since there’s no such thing as a 1/2 pixel (much less 1/5 pixel), ZBrush has to discard a lot of information from the canvas in order to make it all fit onto the texture. The results, as shown on the right, aren’t great. Without the artist’s eye to know what details are important and what aren’t, the discarding gets applied uniformly across the canvas and the results are a lot of pixelation.
Happy ZBrushing!