Min and Max AA Subdivs changing nothing

[klex167]

Hi everyone,
I'm trying to improve my renderings (quality and rendering time) but having problems with the settings.

I can quickly adjust the quailty by changing the threshold.
But changing the min and max AA changes nothing in quality or speed of the renderings.

My intension is to have a good overall quality but difficult areas should break up earlier the calculation.
In my example (attachment) I have a simple cube and a komplex glass sphere. Its obvious that the glass takes very long.
I want to speed up the glass calculation. But it doesnt matter if I use low AA values or high AA values .. its always the same.
The sample element tells me that the calculation reaches the threshold almost everywhere:




If I increase the threshold the speed is better BUT the cube gets bad noise. Anyone a tip for me?
(how can I mange to get the samples red for the whole sphere?)

[sirio76]

Most of the time you should just leave default value and adjust the threshold, there is a good chance that messing with settings will result in longer render time with no significant quality improvements.
To be practical one quick solution to increase/decrease the sampler work on a particular object is to use the rays multiplier inside the Vray compositing tag.

[klex167]

Do you mean the "ObjectProperties-Tag"? I changed the Multiplier values but nothing changes.

But anyway I'm wondering why changing AA Subdivs (in the rendering settings) dont change anything. In the docs (sample rate) its written:
"The suggested way to minimize the red color and optimize render times to increase the Max AA Subdivs value (if the previous render was still noisy), or increase the Noise Threshold value (if the previous render was clean, but took too long to complete)."

[shaio]

With V-Ray 5 a lot of the sampling adjustments are happening automatically under the hood now and this is the reason why you don't see much of the difference. We've also removed the local subdivisions from materials, lights, textures and Render Settings for that reason (you might still find some subdivision settings like the VRayDirt shader for example where the local subdivisions option still works). As sirio76 suggested go with the default values and you should be fine in most of the cases.

[shaio]

As for the red pixels in your refractive object I guess that this is because of the higher refraction depth that you might have set for the material. If it doesn't considerably slow down your render time and you don't have any edges with bad antialiasing I would suggest leaving it as it is. I'll take a look at the scene and get back to you.

[shaio]

I've found the cause of the red pixels, and it is because of the Sun disk. The Sun size is too big (Size 5) for its position and being that big and high makes it visible inside the refractive object. A size of 5 would be useful for sunsets but not during midday. It is normal for V-Ray to try and sample those overbright areas too much because of the high intensity of the light. Tweaking the min/max subdivs won't help in that case, so it will be best if you reduce the Sun size to e more realistic size for its current position.

[klex167]

Wow, thanks Ivan. I will check that.

[shaio]

You can also try and set the Refraction glossiness to something like 0.99 so it isn't so perfectly refractive and that way you will still get rid of the red sampling areas while still having the Sun size set to 5.

Here is a quick screenshot from your scene.

[klex167]

Thank you Ivan,
good tip with the sun! That helped.
With lowering the glossiness I got rid of the red sampling but unfortunately the rendering tilme went up to 200%.

But now I know the background. Thx.

[shaio]

Thank you Ivan,
good tip with the sun! That helped.
With lowering the glossiness I got rid of the red sampling but unfortunately the rendering tilme went up to 200%.

But now I know the background. Thx.

Ok that is odd. I don't notice any render time increase at all. Could you please create a new render settings preset where everything is with default values and only set the sampler to Bucket and do a comparison?