A quick question about pixols…
Does the preview renderer use pixol technology to render the model on screen as well in real time?
When you’re editing a model, you’re looking at polygons. It only becomes pixols if you snapshot it to the canvas.
Thanks for the reply!
So is the rendering system for polys different than for pixols?
I’m asking this because someone asked me about it and my initial reply was that both the pixols and polygons were using the same real-time rendering system. Is that accurate?
No, it’s the same renderer. Pixols are depth-enabled pixels. Therefore, they are seen as 3D by the rendering engine.
Renderers render the pixels that you see on the screen or in the output file. They do this by bouncing light off the information in the scene. From the rendering engine’s point of view, it makes no difference whether the surface is comprised of pixols or polygons.
Consider C4D, for example. You have NURBS, polygon objects, skyboxes, etc. They all contribute to what you see on the screen, but it’s still just one rendering engine.
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Thanks! That’s what I figured, but he didn’t believe me. He had to hear it from a more credible source. 
So when Zbrush is rendering, (even with a tool still in edit mode) it’s rendering everything as pixols? Is that comparable to a true 3D environment where actual raytracing occurs?
I bring this part up because when ever I have a model with 2 arms for example and part of the arm is behind the model, it renders a shadow only for the visible part. Even when the model isn’t dropped to canvas.
Awesome post,Thanks for sharing.
I believe that what’s happening is that ZBrush is using a rendering shortcut known as backface culling. Basically, it doesn’t take into account what’s not visible to the camera. This speeds up rendering, which enhances interactivity.
The Zbrush renderer is very quick-n-dirty, intended only for previews, or generating shaded textures for use with meshes.
Actually, it has a very good renderer and material editor. I’ve used ZBrush’s renderer for several recent illustrations. It just can’t do accurate hard shadows for the reasons listed here (in most situations it’s unnoticable), but it’s awesome for soft GI effects.
But the attached image shows what I’m talking about. Even when the object is not dropped to canvas, it renders as if it’s only pixols. Again, it’s unnoticable most of the time, but something to keep in mind when rendering images in ZB.
Is there a way to turn off the backface culling?
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Have you tried using ZMode under the Light>Shadow menu? You will need to increase the number of rays to get a good effect, which also means decreasing aperture.
ZMode will only have an effect during a Best render.
Yeah, I always have ZMode turned on for lights that point any direction away from the camera. And for lights from behind an object like rim lights, I turn ZMode off, otherwise they don’t do much at all.
That example pic had the light from the right side with ZMode turned on and the number of rays at about 35 with the aperture at about 20.
I just don’t think ZBrush can render anything that isn’t visible on screen whether it’s dropped to the canvas or not. I’m not 100% sure on that though cuz I haven’t read or heard anything that confirmed it.