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View Full Version : Shadow Casting Trick?


Psyhke
02-26-2003, 07:39 AM
Is there a way to have a light *only* cast shadows? Or some trick for getting this effect, or is this a post-only proposition?

alaklij
02-26-2003, 07:45 AM
Two lights sharing exact coordinates.
One cast shadows at 100% intensity
Second light does cast shadows at -100% intensity.
The second light sucks the illumination, but the shadow is still calculated.

MrWyatt
02-26-2003, 07:53 AM
what exactly do you mean. multiple lights and only one cast shadows, one light and it only casts shadows of chosen objects. You can chose which light shall have shadows and wich shouldn´t, you can even tell the light wich object it illuminates and wich it ignores, and you can give the objects the ability to either cast recieve shadows or have selfshadow, or you can disable it. It all depends on what you want.
hope this helps you.

Psyhke
02-26-2003, 08:40 AM
Well.. maybe a better way to put it is that I would like to have a particular shadow be "extra strong". Almost as if you could set your shadow color to darker than 0,0,0 black, to overcompensate for peripheral illumination from other lights, or luminous objects that happen to fall within the shadow, etc.

alaklij, I thought I had something like what you describe working at one point, but can't seem to make it work right now. I'll have to keep messing with it, it's late, and I'm probably not thinking clearly..


PS - I actually just tried the PSD export and messed with the shadow output layer, and am able to do what I want that way. But would be convenient to find a way to do it during render...

Psyhke
02-26-2003, 09:02 AM
*thwap* *thwap* (me hitting myself on the forehead)

It's exactly as you say, alaklij, but you had a typo:

"Second light does cast shadows at -100% intensity."

Missing a "not". Cool, it's working now, thanks.

alaklij
02-26-2003, 05:28 PM
Originally posted by Psyhke
*thwap* *thwap* (me hitting myself on the forehead)

It's exactly as you say, alaklij, but you had a typo:

"Second light does cast shadows at -100% intensity."

Missing a "not". Cool, it's working now, thanks.

Sorry about that. Oops, "not" is what I meant to say.
Glad I could help!

alaklij
02-26-2003, 05:36 PM
Originally posted by MrWyatt
what exactly do you mean. multiple lights and only one cast shadows, one light and it only casts shadows of chosen objects. You can chose which light shall have shadows and wich shouldn´t, you can even tell the light wich object it illuminates and wich it ignores,

In this particular case, if Psyhke were to "turn off" illumination of a given light he would loose the ability to cast the shadow. If he turns intesity down to 0% he looses the shadow as well.

Regardless of all the shadow options for an object Psyhke still needs the light to have intensity and "hit" the object to perform the simulation of a shadow( So that Lightwave a figure out where the shadow goes). The second light at -100% intensity acts like a perfect black hole sucking all the light away, except for the shadow(as long as casting shadows is turned off for the negative light).

BTW, a negative light can also simulate a shadow. And negative lights help eliminate unwanted light in certain areas of a given scene. Sculpting with light, if you will.

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