View Full Version : Polygons acting as light sources?

01-23-2008, 07:47 AM
I don't know if this is possible, but here's what I want to do.

I have an interior scene with several windows which show the outdoors. Outside it is overcast, so what I don't want is to stick an area light where the windows are and have sharp shadows because it won't match the outside.

Obviously I still need soft shadows (the scene will have radiosity) so I can't turn the shadows off in the light panels.

So... is there a way to have the images I'm using for the outdoors to actually be a light source themselves (it's just an image file mapped onto a planar)?

BTW I'm using 9.2.

Thanks in advance :help:

01-23-2008, 12:11 PM
Everything that has a luminosity factor is a light source when using raydiosity (not backdrop raydiosity, though). So you might have to bump up the luminisoty value of those panels for them to generate enough light for your scene. And/or you may have to adjust some of the raydiosity settings to pump up the light.

01-23-2008, 12:19 PM
Some people will use a high res lightprobe as the backdrop and a low res hdri light probe as the light source. I think this speeds up the rendering a bit, if I'm not mistaken.

You can download some highres and low res hdri lightprobes at the HDRILabs.


01-23-2008, 03:32 PM
You can use a single polygon for light with Global Illumination (GI).

Here is a box with only one polygon lit as a photo using 200% illumination.
Other elements were tweaked in order to up the light a bit. Interpolated GI.
About a 5 minute render.

01-23-2008, 04:28 PM
This one's a little smoother.

4096 rays, high MES (500mm), no MPS. about 40 sec render.

01-24-2008, 07:24 AM
Thanks for the feedback, and thanks for the link to the HDR images :)

I'm not sure whether the HDR images will work though because my scene is enclosed in a box.