What is V-Ray RT and who should use it?

- [Voiceover] In its early days, or around beater and version one of the software, V Ray RT was typically thought of and even presented as a Fast Preview Renderer that could be used to speed up the look to phase of a project, the idea being that once approval on a scene was given, an artist could move into the production phase of the project using the V Ray production renderer. As the software gained more features, though, all of that started to change, and V Ray RT began to be promoted as an alternative production renderer in its own right.

It also, rather than being sold as a separate stand-alone piece of software, became an integrated part of the main V Ray render package. All good and well, I hear you say, but what exactly makes the RT version of V Ray different from the production renderer, and why might I want to use it? Well, one of the big differences between RT and the production engine is the fact that RT's actually a path trace renderer, meaning it uses a set of algorithms that are designed to compute lighting in a 3D scene in a matter that is as faithful as possible to the way in which the physics of light work.

To do this, the engine computes the level of illuminance that arrives at every given point on a geometric surface. It then modifies its collected data by applying any one of a number of service and/or volume reflectants and absorption distribution functions, thereby determining how much light needs to be bounced, scattered, refracted, and so on. These processes, when combined with physically accurate models of surfaces, accurate models of light source behavior, and optically correct camera models, can produce still images that are oftentimes very much indistinguishable from genuine photographs.

In fact, path tracing, by default, naturally simulates a lot of the effects that typically have to be specifically added to a render when using more conventional, i.e., ray trace or scan line, computation methods. These effects can include soft shadows, depth of field, motion blur, caustics, ambient occlusion, and so on. The problem, of course, is that all of this cool functionality doesn't come cheaply, although in this instance the currency isn't money but rather time. Path trace engines and especially those that use completely unbiased algorithms are notoriously slow when compared to their much more tweakable ray trace and scan line counterparts, which nicely brings us to yet another big difference between V Ray RT and the production engine, namely, the fact that RT can be used as either a CPU or GPU based renderer.

And of course, with rendering on the GPU, we sometimes get a massive increase in terms of render speed. Before going ahead and switching all projects over to GPU-based rendering, though, do be sure to check out the CPU versus GPU video in this chapter, as there are a number of restrictions and potential gotchas that we will need to be aware of. So who exactly should use V Ray RT? Well, anyone, really, who needs or wants to create photographic realism in their renders. This would include, but of course is not limited to, artists working in product and/or architectural visualization, artists who create broadcast or feature film effects, especially those who regularly need to match CG renders to live-action plates.

In fact, we could say anyone, really, who needs to create what I like to refer to as photographic-looking renders. Indeed, as you watch or work through this course, you will hopefully be able to see just where in your own production pipeline V Ray RT should be able to fit. All that having been said then, let's move forward and take a look at how we go about accessing the RT engine inside of 3DS Max 20016.