lighting help

Does anyone know how to make light from a 3d object look as if it is shining on a real person? Thank you. (CGI/Live Action).

you’ll need to be more descriptive. Don’t know what you’re asking exactly.
Are you saying you want the 3d object to appear to emit light?

I believe so.

The cg created shadows, highlights and reflections are all done with render passes & compositing. But that just sticks both the real image and the cg one together.
What we need to do is create those image artifacts in the first place.

This is done by creating a cg counterpart for the object in the live-shot. Then, the shadows, reflections and highlights that fall on the cg counterpart may be seperated from the rest of the render, before being combined with the real footage.

Say for example, I had a mechwarrior type thing walking in an underground carpark. This bot had flashing lights on it and I wanted these lights to illuminate the carpark, the cars and to reflect off the cars’ windows. I would need to model the carpark and the cars before I could gather the needed images to composite with the real footage. Depending on the final resolution and time that images are in shot, these cg counterparts can be quite rough - quick cleaning up with a 2d program being sufficient processing for the results to be acceptable.

Just think of it as being the same as the process used to make 3d objects look like they’re in a real scene, except in this case, we don’t want the whole object - just the lighting information that it recieves. This is what we composit onto the real footage to complete the illusion.

There’s a (3dsmax) tute in 3D World from Nov of last year. I could scan it if you want vfxjunkie.
Just drop me a pm if you want it.

simon

ah, I understand now. Sorry that’s my fault. Yeah, that’s how it’s done alright. But really, this is quite time consuming to get an effect that can be achieved by faking it.

And if your human moves, then you will need to mimic every movement to the last pixel to achieve a realistic effect. Obviously this is quite involved to get an effect that can be achieved in post production (like with blender nodes and such).

If it’s just one still image, why not save yourself the trouble and photoshop it. If it’s animated, then go with nodes unless you want to spend a week of work just to add a new lightsource to the scene.