View Full Version : Lightening setup problem kitchen scene

06 June 2010, 02:37 PM

I've got a simple kitchen scene that I have to create some nice renders of.
I've set it up with VrayLights (planes) in the windows, simulating the GI (thought it was easier to control it that way). I'm using IES files for lamps over the dining table, in the roof and over the sink/oven. The camera is a vray camera, 1/40s, iso100, f/8.

I've also got another VrayLight (plane) in the roof behind me, to help some.

I've tried to get a nice exposure, but failed as you can see.
And I always fail in this moment, and after that switching over to Maxwell :(

Though THIS TIME I really want to succeed, that's why I need your help here.
What I'm I doing wrong in Vray?
Or is this a pure pre-processing issue?

I'm rendering with Irradiance Map + Light Cache

Here is the render:

And here is a screen of the scene:

Thanks in advance for help!

Best Regards Patrik

06 June 2010, 05:21 PM
I cannot give you a product-specific answer, nor can I therefore point you to any product-specific solution, but maybe I can toss a few useful concepts about this lighting setup.

Very clearly, "what's wrong with this picture" is that the lighting at the end of the corridor is completely blown-out white. A blazing over-exposure.

In fact, almost everywhere I see light I see an over-exposure with a "ker-plunk!" transition between light and non-light. Is this being done with a linear workflow or, as I suspect, sRGB? If you're not working in a linear color-space, as lights "add" to each other the power-curve effect of gamma will bite you in the :argh: very fast indeed.

The first consideration that you should have with regard to any lighting situation is to make certain that the diffuse or ambient lighting throughout the scene is fairly uniform; what Ansel Adams would call "Zone 5." A good, even, realistic coat of base-paint. You have a plausible excuse to add some light to the ceiling, which you need: let's pretend that there are windows at both ends of the room, so neither the floor nor the ceiling need to be (as they are now) "completely in the dark." (BTW: there would never be "the photographer's shadow," either.) Just a good, simple, comfortable base-exposure.

You then need to adjust slightly front-and-back from those levels. Okay, "the floor's a little darker," "the glow around the window's a little lighter and maybe a little warmer." That's how the ambient and diffuse light in the room would plausibly fall.

I suggest that, in this and in all steps, you pay close attention to the "Histogram" tool. You should have a "bell curve," and as you add "a little more light here," look for another place to repay your debt... "about the same less light there." The bell gets wider but remains mostly balanced.

Now for some specularity = highlights. There are some "practical lights" in the scene: fluorescent tubes mounted under the cabinets. They're artfully omitted from the picture but they cast a broad, slightly-green glow on the countertop and the walls behind, and throw just a little light also on the floor. Looking elsewhere, we reason that the top of that stove isn't altogether matte: no, it would definitely have a specular sheen (shows that the kitchen's neat and tidy).

The histogram by now is perhaps a little more active on the right-hand ("bright") side, because you have added light. Don't overlook CG tricks like "spotlights that cast shadows," which can be useful at times. Let the histogram guide you as to just how much light to add. It will be much less than you think.

And this, basically, is how I'd approach the problem. But it's a very difficult problem, and it's because of the room itself.

This room, if it actually existed in real life, would be very problematic to light because of the open window at the far-end, the presumably matching window behind the photographer, and the blaze-of-morning or afternoon sunlight outside (and not a curtain to be found anywhere). Do you have the opportunity to redesign anything, or must you "dance with the one who brung ya?"

06 June 2010, 08:00 AM
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06 June 2010, 06:38 PM
normally if you use the same values in vray and maxwell, the renders will look pretty close.

Are you sure you have set the same values for everything?

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06 June 2010, 06:39 PM
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