Horrible blotches when using DMC Sampler Adaptive = 1.0

[tricky]

Having recently watched a training session in Vray advanced, it was suggested that you should always set the DMC sampler adaptive amount to 1.0 (the default being 0.85).

I tend not to touch this setting too much, but I thought I'd give it a try. When I do, I get horrible blotchiness that to me look like IRmap type (low frequency) noise. In fact, the training session suggested that this type of noise is the result of poor irradiance settings.

However, my settings are not what I consider to be poor:-


Here is a bit of the render to show the problem:-


When I return to the default setting of 0.85, the render is clean. However, I'd like to know what settings I should be tweeking to make the render clean with the adaptive amount set to 1.0.

I guess it could be caused by just not ebnough light bouncing around the space...

[vlado]

If you do set the adaptive amount to 1.0, you will need to increase the "min. samples" parameter a bit. Otherwise, the adaptive algorithm kicks in too soon and may produce very splotchy results.

Best regards,
Vlado

[tricky]

OK, but I have seen a couple of 3dats tutorials where the guy swears by the fact that you should really set the adaptive amount to 1.0, and that Chaosgroup only have it default to 0.85 to 'help along' newcomers top VRay. I have tried upping the min.samples, but you do have to go really high to achieve clean results. In any case, the tutorial advice really pushes the fact that you don't need to touch min.samples at all to get good results, and its really a matter of your irradience settings being too low.

I think the 3dats advice is a little dangerous, especially coming from such an authoritative voice.

[vlado]

Were they using the irradiance map in those tutorials?

Best regards,
Vlado

[tricky]

Irradience and LC.

Its no big deal, and easy to clear up reverting to 0.85 adaptive amount, but I just thought I'd check it out and make sure I am not being stupid.