DMC Sampler

V-Ray V-Ray for SketchUp General
1

I was under the impression that if you increase the Subdivs Mult in the DMC Sampler then it will increase all Subdiv properties globally.

Now I made a test file and rendered with the Mult at 1.0 and then at 5.0 - there is an improvement in the quality of a glossy material I am testing but if I reset back to 1.0 and go into the material and change the Subdiv from 8 to 40 (5x) then the quality is much higher. Shouldn’t this just be a numbers game and get the same result?

DMC Test.jpg
DMC Test.jpg880×568 121 KB

2

I wonder if the material subdivision is specific to glossy reflection, whereas the global dmc doesn’t affect glossy quality. Which parameters are you changing (screengrab of your settings?)

3

It should control all glossy subdivisions.

http://www.spot3d.com/vray/help/150SP1/render_params_dmc.htm

DMC.JPG
DMC.JPG877×156 13.6 KB

ReflectionSub.JPG
ReflectionSub.JPG690×413 33.2 KB

4

Chaos Guys: Where’s Fernando these days, he would know?

5

Hi Valero

The Global subdivs Multiplier, basically multiply all the subdivision in the scene with the exception of LC, Photon map, caustics and anti-aliasing subdivision. So everything else is affected by this option (glossy reflection/refraction, lights subdivs, Irr Map, Brute Force, area shadows, etc.)
Let said that you have a material with glossy reflection of 8 and the Global subdivs Mult is set to 1 ( the default setting for both). The actual samples for the gloss reflection is the square of that number.
So we have this:

Example 1

Glossy reflection = 8 --> 8 x 8 = 64 samples
Global Subdivs = 1
Total samples = 64 x 1 = 64

Example 2

Glossy reflection = 16 --> 16 x 16 = 256 samples
Global Subdivs = 4
Total samples = 256 x 4 = 1024

Example 3

Glossy reflection = 8 --> 8 x 8 = 64 samples
Global Subdivs = 16
Total samples = 64 x 16 = 1024

Notice that the Example 2 and 3 should produce the same result in the glossy reflection.

I hope this can help.

Fernando

6

Always can count on you Fernando. Yes, this answers my question perfectly. So by using 8 and a global subdiv of 5 I was actually getting 320 samples. But when I used 40 and then global subdiv of 1 I was getting 1600 samples. I did not realize the multiplier worked this way. Thanks so much!