Window Area Light Theory

[dx394b]

I have noticed everyone and their grandmother using an area light infront of their windows -and have employed the same technique myself accordingly, but without true understanding.

I am confused about its true purpose. Is it only to add a little extra light to the window sill? Or to add some significant light to the room?

Also with GI if the sun is intended to be the only lightsource in a particular scene then there should only be one direct shadow, so I am also confused as to why shadows are often enabled on these window lights. I understand the use of say a floor, or wall bounce light, but these have me slightly stymied.

Once I understand the theory of their use then I can employ them to taste.

Any ideas on this?

Thanks.

[jameswillmott]

Light is light, regardless of whether it comes directly from the sun, or bounces off something first.

The range of difference in brightness between indoors and outdoors is so much, that all the light bouncing off trees, roads, through the sky etc, has significant effect on internal images.

Since all light behaves the same, it should really be blocked when it hits something, so that's why shadows are turned on for the window lights. All they are doing is simulating the ultra bright world outside. You could do it properly in HDR+radiosity but you have more control with the standard-area-lights-in-the-windows method.

[Iain]

The idea is to simulate the blue ambient light that comes through the opening.
It generally has a falloff that you can see on ceilings and walls so Area Lights with falloff do the job nicely. They also have soft, grainy shadows which gives a nice occlusion style dimension to the lighting.

[Matt]

I use them as the main ambient light coming from outside, backed up with another stronger (and smaller sized for tighter shadows) sun area light.

Then fill in the gaps with big area lights outside the 'room' without shadows so they hit everything, then play with the intensity and falloff (usually linear for these ones).

[Captain Obvious]

I hardly ever use area lights in windows. Then again, I don't really do any interiors with small windows anyway... Most of 'em have HUGE windows, so just radiosity through the window is fine.

[dx394b]

Thankyou for all of your responses, this gives me a better idea as to why or why not they may be used.

As to the contrast of outdoor / indoor lighting, Is there a way to set an actual shutter speed for a single frame along with the F stop? (Apature)

I'll keep playing around with these ideas. Perhaps I'll measure my room and take some ambient only photos then try to recreate the scene in LW.

Thanks again, best of luck to everyone.

[Captain Obvious]

You can set both the shutter speed and the aperture, but neither affects the brightness of the scene. Lightwave does not have an exposure multiplier, either.

[Scazzino]

For animation sometimes even area lights are too slow. I used a light rig of spinning spot lights in each of the windows as well as on each wall/floor/ceiling surface of the room set that I built when making my short film BlastOff!

Here's some background information (http://dreamlight.com/insights/12/3DSetsAndProps.html#roomset) with screenshots and renders showing how I rigged the room set with spinning lights for animation.

[Captain Obvious]

Keep in mind, though, that FPrime with area lights is usually faster than LW with spinning spotlights...

[Scazzino]

Keep in mind, though, that FPrime with area lights is usually faster than LW with spinning spotlights...

Yes it can be, but in my case I needed to use the render farm and at the time FPrime had no network rendering capability. FPrime now does have a limited network render capability, but no UB yet...

[dx394b]

Back to those area window lights... any strategies on the falloff/nominal distance settings. I'm using the inverse distance ^2 but have not settled on a good nominal distance. I understand that the falloff occurs past the yellow circle, and that even though you can play with the intensity OR the falloff and get nearly the same result... it uh.. isn't Really the same in theory. or something... :)

I'm trying to throw a little light on the wall opposite windows without blowing out the window sill itself.

What do you guys shoot for with these?

*has been playing more with sliders and inputs than doing any artwork. Its almost as fun as Microsoft Train Simulator. :)

[Iain]

The problem there is that to get a nice aura of light at the window, the distance should be quite short (2-3m in a normal sized room) but to get effective light on the opposite wall, it needs to be more and that will blow out the window.

The solution is two lights as Matt said above.

[Captain Obvious]

Yes it can be, but in my case I needed to use the render farm and at the time FPrime had no network rendering capability. FPrime now does have a limited network render capability, but no UB yet...
Limited? 90 % of our work is rendered in FPrime on our render farm, using BNR. It's working great.



Back to those area window lights... any strategies on the falloff/nominal distance settings. I'm using the inverse distance ^2 but have not settled on a good nominal distance. I understand that the falloff occurs past the yellow circle, and that even though you can play with the intensity OR the falloff and get nearly the same result... it uh.. isn't Really the same in theory. or something... :)
Actually, the intensity and nominal range are the same thing, more or less. The nominal range is the distance at which the light has the intensity you set up. So with 100 % and 1 meter, anything 1 meter away will be illuminated by the same strength as if you were using no falloff. So if you double the nominal range, you quadruple the intensity. They're pretty much one and the same.

[dx394b]

Cool, thanks for the input, I'll keep tweaking things until I get something I like.

[dx394b]

Hey, as an off topic thing. I do a little composing as a hobby (using reason 3)
anything from classical to techno.

If anyone is looking for an origional score for something let me know. It would be a blast to work on a project for fun.

[dx394b]

Here is a short little snippet of something i was working on awhile back.