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DHudson
09-24-2006, 11:47 AM
Hello-
I need help to figure out some shadows. I have an interior room scene, and I think it is lit fairly well, it just needs shadows from the sun going through window panes.

How do I get the shadows from the windows frames to show? Or from trees outside the room? I am using area lights mostly (because I love the soft realistic interior shadows I get).

Any help is much appreciated.

Thank you!

Sekhar
09-24-2006, 01:33 PM
You can use the so-called "shadow lights."

Basically, you create two identical lights, one with 100% intensity and set to cast shadows and another with negative 100% and set to not cast shadows. The first one will light/cast your shadows and the second one will take away light from everywhere, including the areas of the shadows, making the shadow areas dark. Net result is you just get shadows, no light.

You could parent one of the lights to the other so you have the same orientation, etc.

DHudson
09-24-2006, 02:01 PM
Thank you, Sekhar, for your reply. I will try this out. Much appreciated.

DHudson
09-24-2006, 06:52 PM
Is this the only way to make shadows from an outside object?

toby
09-24-2006, 08:14 PM
I really need to remember that shadow light trick, it sounds extremely useful, but this seems more like a case of needing a brighter light coming through the window, and where you'd see a shadow, it's the same intensity as the rest of the room... yes-no?

DHudson
09-24-2006, 09:12 PM
Right- thats what I need. Typical room lighting, with a shadow cast against a wall or floor of the window panes. I turn up the area lights, set the area lights outside the room, but just get a brighter room with no window pane shadows. What am I doing wrong?

toby
09-24-2006, 09:35 PM
Have you checked :
raytrace shadow checkbox in render options
light properties/shadows tab to make sure cast shadows is on
and objects to make sure they are casting and recieving shadows.

If that doesn't work, try making the window pane polygons double-sided.

Sekhar
09-24-2006, 09:54 PM
He he, like they say: if you hear hoof beats, suspect a horse first, not a zebra... :)

Danielle, in addition to what Toby is suggesting to get the pane shadow, try using a spot light outside the window with a tree pic as projection image - it'll give you a great looking throw pattern. Since you also mentioned tree shadows...

toby
09-24-2006, 10:34 PM
I have a suggestion regarding Area lights, turn down the quality from 4 to 3 or even 2 while you're doing test renders, it will render much, much faster. Then turn it back up for the final, if you need to - 3 is often enough.

Giacomo99
09-25-2006, 03:06 PM
Is what you're getting at that the area light's not casting hard enough shadows? As Sekhar suggested, you might want to use two lights: an area light to get the diffuse quality of sunlight and a directional- or spot-light to cast the shadows.

The point here is to not rely on your area light completely, but to use it to add radiosity effects.

Dave Jerrard
09-25-2006, 08:12 PM
Right- thats what I need. Typical room lighting, with a shadow cast against a wall or floor of the window panes. I turn up the area lights, set the area lights outside the room, but just get a brighter room with no window pane shadows. What am I doing wrong?If your area lights are large, the the shadows of the trees and other objects will be too blurred by the time they reach the room. Since it sounds like you're trying to duplicate the effects of sunlight, here's a tip. The sun fills an area of 1/2 a degree of arc in the sky (so does the moon). This is actually a pretty small area, equal to the apparent size of an aspirin held out at arm's length.

Now to get this same effect in LightWave, just make sure the Area Light looks pretty small from a point of view from the object. If you want to be dead accurate, here's an updated method base on a technique from the first LightWave Applied, where I showed a way to use a Spotlight as a guide for sizing an Area Light. Add a camera and place it somewhere in the area you're rendering, like looking through the window. Target this camera so it's looking at the Area Light you're using as the sun. In the Properties panel for this camera, select Vertical FOV and set this to 0.5 degrees (or set the zoom factor to 229.1817). Look through this camera and scale your Area Light so it just touches the top and bottom edge of the camera's view. Since the camer's vertical field of view is only half a degree, your Area Light will cover the same area that the sun does in the sky. It's a good idea to make sure this light is pretty far away, in order to avoid the problems of having shadow radiating outward rather than all being nearly parallel. If the light's too close, you run the risk of your sun acting more like a street lamp, which can also fill the same angular area. :)

My sun lights are usually place several kilometers away, which tends to be godo enough for virtually all my scenes.

Now you just have to make sure you switch back to your main camera for rendering. :thumbsup:

And as has been pointed out elsewhere, you rarely ever need to use a Light Quality higher than 3.


He Who Has Even Gotten Away With A Quality Of 2 On Some Occasions.

toby
09-26-2006, 12:44 AM
And as has been pointed out elsewhere, you rarely ever need to use a Light Quality higher than 3.

He Who Has Even Gotten Away With A Quality Of 2 On Some Occasions.
:agree:
Especially if your anti-aliasing is high or extreme, which I wish more people would use, for animations anyway -

DHudson
09-28-2006, 03:43 PM
Thank you guys so much. Now my work is cut out for me!