Shadow on pure white background

[phuile]

I want to render an object shadow onto a pure white background (RGB 255, 255, 255), i.e. the surround of the object and the shadow must be pure white. If I illuminate the scene on a pure white background polygon using diffuse frontal light, I encounter 2 problems:

(1) The frontal lighting doesn't guarantee the background polygon will render as pure white because the color is determined by how much light is falling on it.

(2) The need to set the frontal light intensity so as to guarantee that the background polygon renders pure white unfortunately messes up the lighting of the object in the front of the scene that is casting the shadow.

I tried lighting the background polygon using luminosity 100% and diffuse 0%. But the luminosity kills any shadow rendering on the surface.

Is there a way to do this that is reliable and is also able to be manipulated fairly easily?

Thanks,
Petre

[Mylenium]

If you really need control, this would require compositing. Set your BG to black as well as the surface that will receive the shadows. On the advanced tab set the alpha of the surface to shadow density. Done. What you get is an image that contains both your object and its shadow on the ground all separated by the alpha channel. You can now further manipulate this image within LW (image processing) or add whatever you need in another program. If you need even more control, you can always try the buffer savers under image processing.

Mylenium

[munky]

Phuile
this is probably a bit late but, compositing aside.....

don't forget that you can switch your lights to only affect certain objects. So you can light things individually.

regards

paul

[jeremyhardin]

i usually add fog for that effect, and set the minimum just past my object, and the max however far. the fog is white.