Vray ExtraTex Render Element With Dirt map In texture slot causes progressive rendering to hang on pass 0

[gadzooks]

Vray ExtraTex Render Element With Dirt map In texture slot causes progressive rendering to hang on pass 0

[matanov]

Scene please?

[gadzooks]

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[matanov]

VRayDirt subdivs are set to 512 and that's the cause. Why have you set them that high?

[gadzooks]

I thought higher the number the nicer the AO would be. what setting is recommended?

[matanov]

Depends on your scene, but still 512 seems unnecessary high. Try with lower values first (the default as a start) and if you are not satisfied with the result then raise the subdivs.

[^Lele^]

I thought higher the number the nicer the AO would be. what setting is recommended?

The AO map is sampled those many subdivisions for each camera ray.

The default value of 3 subdivs will shoot 9 AO rays per camera ray, and when you reached the maximum default sampling (100 subdivs) it will have cast at most 9 x 100 x 100 = 90.000 AO rays in total.
This, only in the unlikely event that the AO won't have cleaned to noise threshold well before that value.

512 subdivs is 512 x 512 = 262.144 rays, for each camera ray.
Because of how V-Ray works, those rays will *all* have to be cast first, and then V-Ray can check what the noise level is.
So it'd take 3 times the max samples than the default, on the first pass only.
It'd then likely stop sampling it, but the damage by then would be done.
If you had a min AA higher than one, it'd cast all those rays more times than once, compounding the endless wait.

if you have many AO maps around a scene, i can give you a little one-liner script to reset them all to default subdivisions (paste into the maxscript listener and press the keypad enter):

for ao in (getClassinstances vraydirt) do ao.subdivs = 3