Arch Interiors

[craiggorton]

I'm doing a house interior and I'm wondering about lighting. I want to light it with only outside natural light, as if it's a bright snowy day outside and no one is home (with no interior electric lights on).
What's the best way to do this? I have tried rectangular lights in each opening- it seems like I have to be careful- three windows together produce more light than a single door. Do I need to adjust every light?
Should I use portals? What's the difference? If I use portals, what light outside? Directional?
Do I turn on environmental GI for this?
Do I need any lights inside to fake this?
I like to use IM + QMC or IM + LC. Any reason to use one or the other?

Thanks,
Craig

[craiggorton]

Arch Interiors

No tips from anyone? What, is Micha on vacation again?!?

[dalomar_cg]

Arch Interiors

I think Micha is on vaction because I haven't seen a post from him in like 4 or 5 days. Its like he's dropped off the face of the planet (I sure hope not).

Anyway, back to your real question. I did a similar kind of thing for an animation about a month and a half back, but it was with Vray for Max not Rhino. Unfortunately I used some of the features that are available in vfmax and not in vfr yet. I think I was using a physical camera, adjusting the light and dark multipliers, and a few other tricks.

As for what you can do I would definitely use LC for secondary bounces. It actually produces a brighter result then QMC due to infinte bounces. Micha is a big advocate for changing the secondary bounce multiplier to .8 to compensate for this, but if your looking to have a bright interior the you can use this to your advantage (I think you can actually increase the secondary bounces beyond 1 as well). I would also recommend using Reinhard color mapping. This will allow you to increase you light intenstity while managing the amount of the image that is burned. Lastly I would say to use directional light, but you may like the sharper shadows that it produces. I don't really know too much about portals so I can't say much in that respect. Oh and one last thing, with interiors like this one your secondary bounces are just as important, if not more so, than the primary bounces. Thus its important to make sure that they are calculated with more precision than you would an exterior or studio scene. With LC I may add more subdivs and definitely decrease the sample size from .02 to something like .01 or .005 (if your scale is in screen as opposed to world)

From a modeling standpoint you would also want to put white planes for the ground outside, especially if you want the light to act like its a snowy day. This should bounce a significant amount of light back into your interior.

[craiggorton]

Arch Interiors

Thanks dalomar.
I am using LC and will continue to do so.
I don't mind using a directional light.
It just seems to me that a normal house on a sunny day (snow or not) can be plenty bright inside without turning on any interior lights. During the day at my house, I don't need electricity. Yet a single directional outside doesn't seem to penetrate my scene realistically. I find I have to throw in some random point lights hanging in space.
I tried rectangular lights in every opening and got splotchy results but my light subdivs were probably too low. Maybe I'm just searching for a one light quick solution and it doesn't exist.

Look at this photo: http://www.potterybarn.com/content/stylehouse.cfm
It looks very bright outside, but nothing inside is burned out. The light seems to be all natural and everything is lit well. That's the look I'm trying to achieve. So what light set-up?

Also, how much directional intensity vs. environment GI? If I'm simulating the sun on a bright day, how much light comes from the sky and how much from the sun (directional)?

Thanks,
Craig

[dalomar_cg]

Arch Interiors

There really isn't a set rule for balancing GI vs sunlight. It depends on how much you see out. Generally if you only have windows (and I guess you might put a backgound in in post or something) then you can actually bump up GI quite a bit. I would try to increase GI as much as you can without any burning or adverse affects. You may find that GI helps brighten up the scene and backing off your directional light so that you can increase GI may help as well. If you have objects outside that you need to see (like through a sliding glass door) those may get burned by this approach. You can actually render it in two passes. One with the increased GI settings and no exterior elements, and another pass with lower GI settings and only the exterior elements (same camera of course) then put them together in post.

Its probably going to take quite a bit of trial and error to make it work, but it can be done. Your right with increasing the light subdivisons, but this also increases rendertime, so I would leave it for the final, an overnight test, or something. Good luck, and post progress if you can

[Micha_cg]

Arch Interiors

At the beginning of the january the forum was down a few days and after this I was waiting for a news at the home page for the come back. I have overseen, that the forum works again.

My suggestions based on my last tests:

- set an environment color or HDRI (use a blury version for GI lighting)
- use IM+LC
- set secondary GI engine at 0.8
- use gamma output 2.2 and correct all textures with gamma 0.45
- you don't need light portals (also cause wrong lighting because a bug)
- set LC at 1000 and 0.02 - if the light cache show many black points at the end of the calculation, use a higher value like 1500 ...
- set IM -3/-1 sundivs 90 samples 20 0.3 0.1 0.1 - if the lighting looks splotchy, use higher subdivs like 120 or 160 or 200 ... and if you miss small shadow details set -3/0
- if you need sun light, set a directional light

Hope it helps. If you got problems, than post some sample images.

[craiggorton]

Arch Interiors









Here's what I came up with. Thanks for the help Micha and Dalomar.

I did not post-process any images and they were all done without changing any lighting.

My settings:

There are 3 point lights in the scene, hanging in space, because I was not able to get enough light into the house otherwise. I used .15 intensity white lights with 50 subdivs, 24" radius.
The sun is a directional with 30 subdivs, white.
I used a white GI environment with 1.0 intensity, and a sky background.
Default adaptive subdiv sampling.
Default QMC sampler.
I used liner color mapping with colors clamped. I did not gamma correct (I know Micha, but I'm not there yet!)
I used IM + LC, both at 1. I didn't want to diminish the secondary bounces.
IM = -3/-1, 50 subdivs, 30 samples, .3, .1, .1
LC = 500, .02

It rendered in about 20 minutes (each) on a dual core 3.0.

So- I know my materials need work and I need more furniture, but I was mostly studying the lighting. I really think I should be able to light this with only a directional coming through the windows (and there's a huge opening in the ceiling. Why can I not? The direct light becomes burned and the kitchen is dark. Do I need to change the color mapping?

If anyone wants to play with the scene, let me know.

Craig

[Micha_cg]

Arch Interiors

Craig, the gamma 2.2 workflow is important for better lighting of interiors.

The environment intensity can be much higher. Reinhard mapping is good too - with a low burn value 0.6 or lower.

You can send me your scene. Rendering interiors is my favourit topic at the moment. I will apply my setup.

[dalomar_cg]

Arch Interiors

They look really good. Micha's right, Gamma corrected workflow is a MUST for interiors. Without it your fighting the darkness of the shadows and it just becomes way to cumbersome. With the Rienhard mapping lowering the burn value will help, but you can also increase the muliplier as well. This will lighten up the shadow areas even more. With those two things I think you'll find that you won't need the point lights anymore. Besides I don't think they really help the image that muchI definitely would like to mess with your scene a little, so upload it to ftp://asgvis.com/incoming (I hope thats right), just make sure that you include textures as well. Good job and keep working on it

[craiggorton]

Arch Interiors

How do I upload to that ftp site?

And your e-post email is bouncing me, Micha.

[dalomar_cg]

Arch Interiors

First in a window file folder type the ftp site into the address bar. You should just be able to drag and drop into that folder, but once you leave the folder you can't see it. Once you put it in there either send me an email or a PM so I can check and make sure I've got it. It its smaller than 15Mb then you could probably email it to me if you want to. dalomar@asgvis.com if you didn't get it before.

[Micha_cg]

Arch Interiors

Hmm? I got emails today. My adress is:

e - post at simulacrum de

Did you use this adress? Or is the attached file to large? You could upload it at rapidshare.de (very easy) and send me the link per pm.

[archidork17]

Re: Arch Interiors

Thanks for the post, it has been really helpful.

I just want to ask one question in regards to Micha's post on January 31, 2007 it says "use gamma output 2.2 and correct all textures with gamma 0.45."

I can't find the option for gamma correction for textures. please help.

[bdcali_cg]

Re: Arch Interiors

When loading an image (bitmap) into your material slot (click the 'm' next to the color window in the Difuse/Reflective/Emissive/Refractive layers - set pull down to 'Bitmap'), you will see an 'Override' option. This is the Gamma override, which by default is set to Gamma 1 (Linear). If your bitmap hasn't been Gamma corrected (still set to Gamma 2.2) with an image processing program prior to its use in Vray, you will need to correct the gamma by applying an inverse curve. 1/2.2=.4545

Vray assumes it is working with 'Linear' input, therefore applying a reverse curve Linearizes your image. Currently we have to do this correction for every image, however there have been discussions that in future releases this will be a Global Modifier for all images.

[dalomar_cg]

Re: Arch Interiors

The Global Gamma controls will be in the SR. There will be an option to correct all LDR textures (jpegs, png, bmp, but not hdr) and an option to correct all of the colors. This option is already in VfSU and will make its way over to Rhino.