View Full Version : Help with shadows Please!

02-17-2003, 11:14 AM

I have an intersting question fr you lightwave gurus out there. I am a former maya user who has defected to lightwave
and I am finding it pretty kick arse! My question is, If I have nothing but a character and a single polygon
under his feet for a ground plane, and white as my background in backdrop, how do I get just the character and his shadow that is cast from a single light source to render? I don't want the polygon to be visible, just the shadow casted on it. In Maya it was just a shader called "Use background" is there any lightwave equivelent?

Thanks in advance guys

02-17-2003, 11:53 AM
Set alpha channel to shadow density in the ground plane's surface properties (under advanced tab) and you're set.


Global Hawk
02-17-2003, 12:00 PM
Yep! What he said sould work!;)
(Sorry, had to put in my little comment!):D

02-17-2003, 06:44 PM
Hmm, i tried that and it only changes the alpha channel so its fine if your compositing the image but not if your just wanting to render an object onto a white background but with some shadow.

When iv done this in the past i had to use Worleys Gaffer and Enable the "Luminous Shadow Darkening Tool", this makes the object 100% its base colour with no shading other than any shadows cast onto it.


02-17-2003, 06:48 PM
Like the image.

Iv also used this with front projection mapping to cast shadows onto background images. U can do it without gaffer but i found front projection mapping always leaves a visible edge on the polygons but using gaffer removes them.


02-18-2003, 07:36 PM
Thank You Guys!

I don't have gaffer so the front projection will have to do, its actually pretty good even though I get a line cuz alls I need is the image, plus the correct colored shadow against my backplate. Then with the alpha created by using shadow density I can then composite this in after effects to create the correct image. :)


02-19-2003, 07:20 AM
I have done this same thing another way -- it's a kludge though -- I think that was in LW 3.5, and all this Alpha stuff probably wasn't there, or I didn't know about it.

Just make a polygon the shape of the top profile of the vehicle, and parent it to the vehicle. Place it under the vehicle where the shadow should be, and make it a suitable colour / transparency (or dissolve, I guess it was). Use the Transparent Edge shader to make the edges of it soft.

Move the shadow off center a bit so that it falls in the reight place relative to the light source, and tada! Now all that remains is to animate it a bit as the vehicle travels -- just so that the shadow moves as the vehicle turns and stuff... but it was surprisingly easy, and gave me a very nice result...

02-20-2003, 08:33 AM
tonyg thats a good idea, i think the best place to use that now considering the other ways to do it is when u want a car for example to appear to be traveling over a bumpy, hilly road. Rather then having to model the road just to have it made invisible to catch the shadows u can just have the car move as if it was going over the bumps and the shadow follows it :)


02-20-2003, 01:39 PM
I suppose you're right... a good kludge is a very satisfying thing ;->