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Questions regarding Direct Light Kernel in Octane Render

Posted: Sun Oct 12, 2014 7:36 am
by rashadcarter
Hiya,

New to Octane generally. I am interfacing with Octane via the wonderful Octane Render for Carrara Plug-in.

I am looking for someone to slow it down for me and give me the parts everyone seems to understand except me.

There are 4 different types of GI offered in the Direct Lighting Kernel. But for the life of me I cannot get transmissive and transparent objects to look as they should.

Below I have included three versions of a render project I've undertaken recently. The first render is PMC, which is by far my favorite Kernel. The second render is the exact same scene and settings except that I have used Direct Light Kernel with Ambient Occlusion GI mode. In the third render I have used Direct Lighting Kernel again, but with Diffuse.

My issue is that in neither of the Direct Light kernels do a very good job of the transparency of the wine glasses. And additionally, neither one seems capable of allowing any light in from the outside. In the Ambient Occlusion version, there is no transmission through the lamp shades,and no skylight or sunlight coming in through the windows. In the Diffuse version, I can get some light into the scene because lamp shade transmission seems to work with mesh lights in this mode, but I still have no light from the sky or the sun penetrating the windows.

So basically, instead of clear looking glass I get these silvery looking surfaces that don't really seem that transparent unless you view them at certain specific angles. And again light doesn't seem to travel through the windows as expected.

Am I to assume this is more of an issue with interiors than with exteriors? In scenes where the sky is open and visible everything looks fine but not for interiors? I'm really confused. And to top it all off, on my Titan Black it seems that PMC actually renders many times faster than direct light Diffuse mode.

So I'm really confused, but not confused upset, confused excited. Just want some help getting to grips with it all.

Please help me to know if these results are typical or am I doing something wrong? Any help will be greatly appreciated. Thanks all for your time.

Re: Questions regarding Direct Light Kernel in Octane Render

Posted: Sun Oct 12, 2014 8:17 am
by rappet
Hi,

I am also struggling with interior renderings and good lighting and good transparancy on windows.
I am doing better and better, but there are guys out there that can give you good advice.

Just two links for you that might be interesting.

My first struggle getting good interior (clipped background to get more rays inside and added emitters)
http://render.otoy.com/forum/viewtopic. ... et#p194539

About fake shadows to let light theough:
http://render.otoy.com/forum/viewtopic. ... ws#p205863

Cheers,

Re: Questions regarding Direct Light Kernel in Octane Render

Posted: Sun Oct 12, 2014 8:37 am
by prodviz
Upping the specular depth might help a little with the wine glasses.

Re: Questions regarding Direct Light Kernel in Octane Render

Posted: Sun Oct 12, 2014 10:59 am
by DayDreamer
There is a big difference between DL and PMC/PT, DL doesn't refkect already refracted lightbeams. I had problems with two transparents touching like Wine+Glass - Light coming through glass AND reflected(refracted) by wine wasn't there with DL, but was apperent with PT.

Just play with a simple build to see what Kernel setting does.

Also, IndexOfReflection is to be played with.

Still, it can be material issue. Either you can have Diffuse with transparency, or Specular with refraction (IOR decides whether it looks mirror- or glasslike)