Interior, GI only?

[mtbmarsh]

Hey guys,

I'm trying to create an interior rendering, but with GI only. I'm trying to look at the spatiality of the interior, so I've also overridden the materials in Options panel. It is a fully enclosed box, so is there any way to have it lit...i.e not a 100% black render? There are very few windows, and i've overidden thematerials, so there is nothing from the outside coming in...

[Micha_cg]

Re: Interior, GI only?

Best you hide or delete the window glass. Glass isn't visible from inside. If you use a HDRI or physical sky, than you should get light in to the room. Try IM+LC and use a high subdiv count for the IM (80...300) if you get blotches.

[dalomar_cg]

Re: Interior, GI only?

Several things...If you're overriding materials, then just hide the glass object.

If you want to do just GI, then you'll want to greatly increase the GI level. That will get more light into the room, which will help.

Set the Adaptive Amount to .95 at maximum, with .9 or .85 being the best. An adaptive amount of 1 (which is the default) in a dark room will lead to artifacts no matter how many hsubdiv are used.

Use LC for secondary bounces...LC will bring more light into the room, it will be faster than QMC, and you can increase the secondary bounce multiplier beyond 1 if need be.

[Micha_cg]

Re: Interior, GI only?

..
Use LC for secondary bounces...LC will bring more light into the room, it will be faster than QMC, and you can increase the secondary bounce multiplier beyond 1 if need be.

Are you sure? This cause, that light indirect bounce much to much. This should cause a dull, flat look. I recommend to set the sec eng multi at 0.8 for interiors, this helps to get a good contrast in dark parts. If more light is needed, that increase of the environment intensity should be the best way. Against burn out around the windows it helps to use a lower burn value for the the reinhard colormapping (default 0.8, but 0.6 could be good too).

[dalomar_cg]

Re: Interior, GI only?

LC will always calculate for all indirect bounces no matter whether its being used as primary or secondary. Thats why I use .8 for the secondary multiplier to counter act for that (thanks for that trick). But its actually quite useful because you can bring more light in if you need it, so thats more or less what I was suggesting. There are other ways to get better/different contrast that involve messing with color mapping stuff (light multipliers, dark multipliers, burn values and other stuff).

[Micha_cg]

Re: Interior, GI only?

I start a quick test with an old scene, because you makes me intrigue.

sec multiplier 0.8


sec multiplier 1.2


Hmm, the shadows get more energy. Light bounce more than physical correct. I would avoid it. ;o)

[dalomar_cg]

Re: Interior, GI only?

For that test I would avoid it too, as there's already quite a lot of light coming into the room. It is something I would only use in situations where there was very little external light coming in. As always, if you stretch things beyond what is the "physically correct" setting, there will be some tweeks that have to happen.

[Micha_cg]

Re: Interior, GI only?

New test with small openings. I changed the lighting to the physical sky now. Multiplier 1.2 and the room is full of light, the red color of the couch tint the whole room. Not looking like real, but interesting.

[dalomar_cg]

Re: Interior, GI only?

Not looking like real, but interesting.

There would need to be a few tweeks (maybe prepasses without the red material on the couch), but if you were trying to make things look brighter without adding more light, it can work. One of the things increasing secondaries would allow you to do is decrease the burn coming from the window without having to sacrifice illumination within the room.

[Micha_cg]

Re: Interior, GI only?

I think 1.2 cause an extrem effect, but good to know. The experiment give me an impression of the power of this option. I think, a light tune can be good some times.

I took both images and use the 1.2 version as layer set to 30% and adjust the colors a little ...