"Use Irradiance Map" Option -> Brute Force

[Junglejuz]

In a large architectural interior scene I've un-ticked the "Use Irradiance Map" option on an object that has fine detail. The irradiance map just wasn't cutting it but now it's tacking ages to render. My question is which value now controls the Brute Force subdivisions used to calculate it's GI? Is it the Max Subdivs value of the Adaptive DMC image sampler?

Justin

[3LP]

I'm just guessing here, but it would make sense if Vray would ready any already set in info.
So uf you switch from IR to BF you should access the BF subdivs. Ince that's done, just switch back to IR.
I have been using this for quite a wile, really not sure if it actually works like that, if not, I've been under placebo for a ling time

[super gnu]

actually once you have the saved irradiance map, it works in a strange way.

to control the bf subdivs on the bits that are bf only, you set the irradiance map to "from file" and load your saved imap, then use the imap subdivs setting controls the BF subdivs for the objects with "use imap" unticked.

wierd i know!

another alternative is to use the vray object properties, and set a gi subdivs multiplier to reduce or increase the BF subdivs for that object.

[Junglejuz]

Wow. that is very weird! How did you find this out? Is it documented somewhere?

[Joelaff]

You could also try detail enhancement mode, which uses IR for the broad areas, but BF for the finer detailed areas. It renders slower, but looks better.

[Deflaminis]

actually once you have the saved irradiance map, it works in a strange way.

to control the bf subdivs on the bits that are bf only, you set the irradiance map to "from file" and load your saved imap, then use the imap subdivs setting controls the BF subdivs for the objects with "use imap" unticked.

wierd i know!

I wonder if the subdivs multiplier affects this. Interesting tidbit here.

[Junglejuz]

Yes, but you can't specify which objects to use detail enhancement on. It's an all or nothing affair.

[svetlozar.draganov]

Wow. that is very weird! How did you find this out? Is it documented somewhere?

I don't think that this is documented into our docs - I'll make a note to add this information under the Options section of VRayMtl:
http://docs.chaosgroup.com/display/V...RayMtl-Options

[svetlozar.draganov]

Use Irradiance Map description is updated as follows:

Use irradiance map - if this is checked, the irradiance map will be used to approximate diffuse indirect illumination for the material. If this is off, brute force GI will be used in which case the quality of the brute force GI is determined by the Subdivs parameter of the Irradiance Map. You can use this for objects in the scene which have small details and are not approximated very well by the irradiance map.

[Junglejuz]

Thanks for clarification Svet.

[Micha]

That's quite bad, an independent control would be much more useful. I use 200 IM subdivs for an interior shot and like to disable the IM for some objects. But 200 BF subdivs are to much, the calculation is extreme slow. I use Vray for Rhino. Do I miss a material based IM control? For example how to get 32 subdivs for the BF objects only?

[super gnu]

you calculate the imap with 200 subdivs, save it, then use the saved imap for rendering, and set the imap subdivs to 32. this obviously wont affect the saved imap.


alternatively (and probably better) you could set the per-object subdivs multiplier to .25 or something.. with 200 imap subdivs that would give you 50 subdivs on your specified object.

however in the latest vray that multiplier now also affects all other subdivs f.e. reflections etc, so im not sure how that would affect the quality of the rendering..
edit: just seen you use rhino, i dont know about the per-object setting there..

[Zdravko.Keremidchiev]

edit: just seen you use rhino, i dont know about the per-object setting there..

Unfortunately V-Ray for Rhino doesn't have per-object subdivs multiplier option.

[super gnu]

ok so in that case, use my first option.. precalculate imap then use that. it works fine.

[Micha]

Thank you for the hints. Stay to hope that subdivs multiplier will be added to VfR soon, shouldn't be so difficult.