Primary visibility slow down

[bigbossfr]

Hi.
We have a render time problem.
The time to render an object (a proxy) + floor in occlusion is : ~ 30 min

If i set my object to primary visibility off (to have just the occlusion on the floor), the render time is.... ~4h.

Same problem with a shadow pass on the floor, etc etc...

Why ?

Edit : it looks like when you set the primary ray to off, Vray do not skip the object in the primary ray, but add a transparency to the object (controled by the max transparency level) o_0 ???
And if you have a lot of primary visibility to off, you get a big slow down ? (it would the inverse in other engine, more primary visibility off, more quick to render)

[vlado]

This is correct - V-Ray will treat primary invisibility as the object(s) being fully transparent, which turn, tends to be slow depending on the complexity of the invisible object. I know that this is not the best approach and we have some ideas how to improve this, but for the moment this is how it works.

Best regards,
Vlado

[bigbossfr]

Yep.
The problem is for example, this isn't work when we have a forest or a lot of objects. We have two problem :
- if we set the "normal" number like 100 in the max transparency, we have a lot of artifacts (and it is very slow).
- if we set a number like 1500, the render take to many time (to many hours).

It is a big problem currently for production.

[vlado]

If your forest is made up of V-Ray proxy objects, or of instanced objects, we might be able to think of something relatively quickly.

Best regards,
Vlado

[bigbossfr]

Yep, all are proxy objects.

[brainspoon]

Any progress on this? Just experienced the primary visibility slow down myself.

[vlado]

For proxies - yes, we will fix it.

Best regards,
Vlado

[bigbossfr]

Perfect ! I will test soon on a "big" shoot.