Hello all,
I heard more then once that you can have an infinite number of polygons with Ray-Tracing, because you’re not rendering the polygons, you’re just rendering the rays. Is this true? Does that mean games can have the same amount of polygons as the movies?
And is there a way I can take an image of my model from Zbrush without using another programme? Sorry, I’m still kind of new to this 
Basically the better the quality the longer the render can take. Large renders in the HD size range with reflection, refraction or elements such as haze or fog can take many hours.
ZBrush does wonderful renders but requires a different mindset when planning the render as it is 2.5 D ignoring what is behind objects. For Illustration ZBrush is actually superior in my opinion. Great results with less effort and time.
For photo realistic renders it is usually best to render elsewhere although good approximations can be done in ZBrush. ZBrush is more of an artists tool than an attempt to accomplish photorealism.
As to the Polys. The number does effect the rendering times due to the polys determining the results of the ray-tracing. What effects it even more though are things like transparency and reflections.
There is a dedicated ray-tracing unit in the works I read about a couple of years ago, but I have not seen it anywhere yet in the marketplace. It is supposed to allow real time ray-tracing. I know Boeing is using it for their engineering but I have no idea when it will be reality for us. As I recall they were using real time ray-tracing with 40 and 50 million poly models. Of course Boeing Inc. has computers we could only dream of.
This Wiki article gives a great explanation now that I’ve confused you -
http://en.wikipedia.org/wiki/Ray_tracing_(graphics
For rendering in ZBrush go to Pixologic.com and see the learning materials and Wiki. Everything you need to learn ZBrush is either there or on here to be found with a search.