Photorealistic Lighting in Production

[ExP]

cginfilm,

My best advice to learn CG lighting would be to step back from CG and take some Cinematography and lighting classes and/or books.

What the best CG lighting artists are doing in big VFX, is simply replicating the same thing they would do in real life. If you are building a CG set, just light it as if it where the real thing. You can start form there and then learn the art of "cheating" real life...

Also, don't be too concerned about fancy features like HDRI and GI. You might be surprised, but most of the big FX shots in Hollywood films use simple lights and many tricks.

Cheers

[LowJacK]

Here is a technique that you can try.

For lighting a set or character, aside from passes like your Sky wrap, Dirtmap and Depth, render and Ambient and and RGB pass. The ambient pass is straight texture. Turn scene ambience to 1,1,1. The RGB pass is your lights. Have your key light (diffuse only, no spec) set to RGB 1,0,0. Your fill lights (again diffuse only) RGB to 0,1,0 and a spec (onyl spec/no diffuse) light thats RBG is 0,0,1.

Use a comp package like Shake or the XSI FX Tree to isolate each colour from that RGB pass (swap component node in FX Tree), use a luma extract to get an alpha for it. By using a colour correct on the ambient pass and an over with your RGB alpha plugged it, you can now change the colour of your lights without having to re-render. You can adjust the luma extract to control how much light is being effected in each area as well.

I just finished a production as lighting supervisor and this is the method I chose to use. Our client and art director had problems making up their minds plus we were on a tight schedule. This allowed my crew to change whatever needed to be changed without having to waste time with multiple renders.

[revilo3D]

a bent normal pass provides similar results.. but i think the poor lad aint even up to passes!

you can easily create photorealism if all the photographic elements are taken into play -

-texture goes hand in hand. bad texture and it will never sell...
- importance of natural shadows.
- camera aberation, dof, grain
- bouncing of light
- colour of light (almost never ever white)
-Finally good composition and real world light techniques to hit it all home..

this should get going

[scottsch]

Here is a technique that you can try.

For lighting a set or character, aside from passes like your Sky wrap, Dirtmap and Depth, render and Ambient and and RGB pass. The ambient pass is straight texture. Turn scene ambience to 1,1,1. The RGB pass is your lights. Have your key light (diffuse only, no spec) set to RGB 1,0,0. Your fill lights (again diffuse only) RGB to 0,1,0 and a spec (onyl spec/no diffuse) light thats RBG is 0,0,1.

Use a comp package like Shake or the XSI FX Tree to isolate each colour from that RGB pass (swap component node in FX Tree), use a luma extract to get an alpha for it. By using a colour correct on the ambient pass and an over with your RGB alpha plugged it, you can now change the colour of your lights without having to re-render. You can adjust the luma extract to control how much light is being effected in each area as well.

I just finished a production as lighting supervisor and this is the method I chose to use. Our client and art director had problems making up their minds plus we were on a tight schedule. This allowed my crew to change whatever needed to be changed without having to waste time with multiple renders.

Interesting way of doing it. When you render shadows with this technique, are you getting your soft shadows with area lights, blurring in post, shadow maps, or some other technique?

[rendermaniac]

If you are rendering out monochrome lighting passes and colouring them in 2D then you have to watch out for transparent surfaces and aliasing at edges. If you can get away with it fine, but if you are doing something like hair then you will really see problems.

You may also have problems if you want to do any sort of volumetric shadows.

This is because you loose the transparency information for each surface which you need to do this properly. The alpha channel is pre-mixed and does not let you unmix it.

Peronally I would not recommend this approach. Any passes that add together (diffuse, spec, reflection etc) can combine together in 2d find as they are already pre-multiplied.

Simon

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