View Full Version : How to lit a scene with a picture

06 June 2009, 04:55 PM
Hi, I was wondering how to use a picture to lit up a scene. I know that there is an option (image based lighting) but that is not possible in my case i think.
Here is why - I have a scene which has a window and outside the window I have a plane with a texture of sunset. And I need the room to be lit by the sunset (ie. the picture that is applied as a texture on the plane). What is the best way to achieve this? Thank you very much for any advice

06 June 2009, 09:02 PM
To make the picture emit light, you should turn on mental ray under your render globals.
Also, you should have a light which casts shadows in your scene. Apply your picture to a surface shader and apply the surface shader to the plane. Turn off cast/recieve shadows under render stats of the plane, and enable final gathering under mental ray's indirect lighting. Render and see if that works for you. If it's too dark, you can turn up the value of the colours in your sunset picture

06 June 2009, 10:21 PM
thanks for tip.

I did try it but there is a slight problem. The only way to achieve a decent ligth is when i put the value on colour gain to about 50 which completely messes up the picture (ie. is unusable as a background but the light kinda works). Is there another way how to preserve the background picture and increase the intensity of the light?

here is a screen so you can see what i mean

06 June 2009, 10:26 PM
A bit hard to tell, but maybe the picture is too far from your objects? try to move it as close as you can

06 June 2009, 10:39 PM
it is just in the window. I thought that i could bump the value up and use it as the light source and hide it and then use another (same picture) as the background but the bumped one creates trouble as the light becomes very low resolution as you can see under the guys head on the left.

06 June 2009, 06:05 AM
IMO it's not worth it doing it that way. Just use an orange directional light. Much easier.

06 June 2009, 09:48 AM
You can use an image (loosely) as an emitter in Final Gather by connecting its file node or alpha node as an ambient and/or incandescent node.

If you're using IBL, the image will drive the photon/light emission. Can be helpful and add realism sometimes, especially for macro or close-focus shots.

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06 June 2009, 09:48 AM
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