An In-depth Look at Image Sampling

Introduction
This article was written to clear up some misconceptions about the V-Ray image sampler and was a direct response to a thread posted on the Chaos Forum (click here to view thread). In this thread, several users found the explanation of the image sampler in the article Critical V-Ray Settings very helpful but were confused about why certain settings were recommended. In this article we (3DAS) wrote,

By default, the Min and Max values are 1 and 4 respectively, which provides decent quality for test purposes. However, these values will often need to be raised for production renders. Values such as 3 and 6 are typically good settings for most production purposes. Caution should be taken in using higher values than 6 because of the possibility of excessive render times. Additionally, it is a good idea not to separate the Min and Max values by more than 2 or 3. Doing so can result in a wide range in quality of detail because it leaves VRay more room to guess incorrectly.

In the Chaos thread, somone wrote-

ok after extensive testing, that qmc setting does not make sense - its faster to do min 1 max 6 and the quality does not suffer which is what the document suggests

Another wrote-

I totally agree about with that as well. I was using Min 1 max 10 with the to get my glossies nice and smooth, and to give the QMC sampler enough room to sample adaptively for good results. After reading the PDF I tried Min 4 Max 6 settings and it increased my rendertimes with no visible difference in quality

Followed by many more like-

But then I started thinking (must remember to engage brain before fiddling) and looked again - so the pshot is the guys at cgarchitect need informing they are wrong on that point! - though I guess it depends a bit on what their qmc adaptive settings were

Many good points were made in this thread but a lot of assumptions were also made. Hopefully this article will help clear up the subject of image sampling. I would argue that image sampling is the most important and least understood feature in V-Ray. If you do not conduct good image sampling, having extremely high quality settings in other areas of the program (like irradiance maps and the QMC sampler) will do you absolutely no good.

See the rest of this article at http://www.3dats.com/tutorials.asp#week17

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Critical V-Ray Settings

Introduction

To say that VRay is a complicated program would be an understatement! Ironically enough, however, it has become the most ubiquitous engine in the visualization industry because of, among other things, its simplicity. Although it contains a large number of settings which should ideally be separated from critical settings and grouped into an advanced section all alone, it is nonetheless a fairly easy program to digest when you know which settings are critical and which can be left for exploration down the road.

We believe knowing VRay means knowing how to troubleshoot your scenes. When you render a scene, you either get a result you want or don't want. If you get what you want, great - but if you don't, and don't know how to fix a problem, such as blotchiness, noise, flickering, etc, then you are bound to spend precious time testing numerous settings. Even when you do get the results you want, you may not realize that you can achieve the same or better results in less rendering time.

Rather than explaining the critical settings in a top to bottom manner, starting with the top-most rollout and ending with the bottom-most, this discussion presents VRay features in a more logical manner, from most critical to least critical. For example, there is an option to disable glossy effects in one of the first rollouts, Global Switches; however, it wouldn't make sense to discuss an option for a concept that has yet to be explained. Therefore, such a setting is reserved for later.

For the purpose of this discussion, we are defining critical settings as those which tend to require attention at least once during the course of a typical visualization animation. This means that while a particular setting's use may not be guaranteed during any given visualization, its use will probably have been at least considered as an option because of its special qualities or characteristics that it offers a user. By the same token, having not listed a setting does not at all mean that it is not something worth exploring, but rather it is a setting most likely not as widely used, as unique in its affect, or as practical in a production environment.

See the rest of this article at http://www.3dats.com/tutorials.asp#week14

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