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erikals
11-17-2010, 12:53 PM
in real life, an object that is red, casts a red shadow (yep, it does, it doesn't need to be transparent, give it a try...)
...in Lightwave however, it does not.

i wonder, why is this?
anyone knows?

http://www.newtek.com/forums/attachment.php?attachmentid=90060&stc=1&d=1290023584

3DGFXStudios
11-17-2010, 01:25 PM
It does not cast a red shadow :D. The only thing that can cause colored shadow is reflection. Diffuse reflection like radiosity. Or it has to be transparent. Shadow is the lack of light. The colored radiosity spot you'll get isn't shadow, it's reflection.... Montecarlo Radiosity does this best..

Traveler
11-17-2010, 01:29 PM
Colored shadows? If light doesn't have a color, how can the shadow be in color (other than diffused reflection)?

Dexter2999
11-17-2010, 01:29 PM
it does not cast a red shadow :d. The only thing that can cause colored shadow is reflection. Diffuse reflection like radiosity. Or it has to be transparent. Shadow is the lack of light.

+1

erikals
11-17-2010, 04:19 PM
it does, try it... probably red light rays are bounced off in the process...

Tobian
11-17-2010, 04:33 PM
It won't cast a red shadow. it would receive fill light from the light bounced from the wall, onto the back of the ball, and in turn back to the wall. To get effects like this to work more correctly, work in Linear Gamma colourspace.

Lightwolf
11-17-2010, 04:42 PM
The only way to have a "proper" red shadow there (not taking diffuse bounces or translucent surfaces into account) would be red light cast into the shadowed area. ;)

As mentioned before, a shadow is the absence of light. And an opaque object blocks all light - so whatever tints the shadowed areas must come from anywhere else but the other side of the object.

Cheers,
Mike

erikals
11-17-2010, 04:43 PM
hm, i'm sure it did, i'll have to get back on it once i get a test-object and a camera...

Sensei
11-17-2010, 05:24 PM
in real life, an object that is red, casts a red shadow (yep, it does, it doesn't need to be transparent, give it a try...)

Tried and nothing (maybe current night artificial light from lamp doesn't have this feature.. ;) ).. Make photo..

RebelHill
11-17-2010, 05:35 PM
yeah... coloured shadows... no, not in the real world.

You often see a similar effect on stage (as in theater) where a coloured light is illuminating an area that's shadowed from another light, and you appear to get a coloured shadow.

But if you really want to create coloured shadows, lights in LW have an option to shadow tint anyhow, so it is in there.

Lightwolf
11-17-2010, 05:38 PM
But if you really want to create coloured shadows, lights in LW have an option to shadow tint anyhow, so it is in there.
Either that or duplicate the light... one being pure red and not casting shadows, the other being pure cyan (blue + green) but casting shadows.

You still wouldn't get the occlusion that's in the render though ;)

Cheers,
Mike

JonW
11-17-2010, 06:59 PM
If one has spent some time looking at paintings from the old masters. The shadows invariably have a hint of purple.

Tobian
11-17-2010, 07:54 PM
Shadows can of course have colour, but only in terms of indirect lighting bounce. Actually, thinking about it, you're less likelly to get a colour bounce from that red ball in LCS, because that's more realistic: The area of white-light bounce from either side has a MUCH greater area than the red ball does. Actually this is one of the advantages of LCS, that colour bleed is LESS bad, and it was a big problem, in terms of the relative weight of bounce light.

If there's not any red-bounce in there it's likely because there's not meant to be. If you need it to be there, try cheating!

3DGFXStudios
11-18-2010, 02:25 AM
hm, i'm sure it did, i'll have to get back on it once i get a test-object and a camera...

You must have been a sleep during science lessons :D

zardoz
11-18-2010, 05:31 AM
If one has spent some time looking at paintings from the old masters. The shadows invariably have a hint of purple.

usually to show the effect of the sky as a fill light

Danner
11-18-2010, 07:40 AM
Some surfaces like flower petals are not transparent but are translucid, in a sense they are bright on the underside and as such they tint the shadow

Lightwolf
11-18-2010, 07:44 AM
Some surfaces like flower petals are not transparent but are translucid, in a sense they are bright on the underside and as such they tint the shadow
Which also means that they're not opaque though ;)

Cheers,
Mike

prometheus
11-19-2010, 03:50 AM
It reminds me of the radiosity luminosity or freflectance of material.

http://www.worley.com/E/Products/fprime/videos.html
http://www.worley.com/Media/animations/fprime/FP3_RadiosityThings.mov

Michael