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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