Controlling lights in compositor?

Hi,

is it possible to control diferent lights energy and color while compositing an image?

This tutorial covers using light render layers to adjust the lighting in the compositor http://www.cmivfx.com/tutorials/view/255/Blender+3D+Compositing

Currently I can not afford to buy this tutorial and i just started to work on a promotional video for a local company. Is there somewhere a similar tutorial, or could someone try to help me over private conversation.

you should render every white (!) light separate (3 lights = 3 images)
conserve your result as float RGB (EXR) or composite direct without saving
now you should be able to change image color (=light color) and light intensity (brightness or multiply-factor) of every image
mix this images you like

Lamp layer passes then?

It actually can be simpler than that…

First of all, always generate “MultiLayer” (OpenEXR on steroids) files for everything you do, up to and including the “final result,” subsequently generating displayable files merely as an afterthought.

Throughout your workflow, cleanly separate the various pieces, using RenderLayers etc, so that you have each component of the overall data stream in addition to “the one final combined result” whatever it may be. In other words, you really want to know, for each light, “what does this light contribute to the result?” Where are the pixels that are affected by this light? What did this light do to the value of that pixel?

Between RenderLayers and this file-format, you can have all of these various streams of data available to you, all at the same time, all in very high numeric resolution.

If you’ve got that separate piece of data available to you, “isolated and pristine,” then you now have the means to manipulate it subsequently. You can get “just that” data out of the file, feed it through noodles to your heart’s desire, and generate from it a new file with a new result … without, please note, losing or in any way affecting what you already have. If you keep meticulous records, and you never throw anything away, you never cut off any of your available options no matter what you do.

Think: multi-track recording. One guy’s sitting in a room by himself with drums. Another guy’s sitting in a room by himself with his guitar. The singer’s in a room by herself. Everyone’s got earphones on. They all play, they all hear “the mix” in their “pots,” and in the control room, what have I got? Four new tracks: each pristine channel, and the scratch mix that the performers are listening to. “Okay, let’s do another take, please.” Now what have I got? Eight tracks. One more take? Twelve.

Now let’s take the best drum-only take, the best guitar-only take, the best vocal, blend them together. Oops! The singer “clammed” a word on take 2. Slice it out of take 1 and paste it into take 2, producing a new sound-file with that result. Constantly producing new data sets and discarding (almost) none.

That’s how you make a hit record, and maybe five versions of that record, always moving steadily forward, always with an exit strategy, always able to come back to it.

Not sure if this is what you’re looking for, but the Color Balance node gives you a lot of control over color and lighting. The three color wheels control the color of the shadows, midtones, and hilites, and the three vertical grayscale sliders act as a Levels adjustment.


Steve S

The tutorial Richard referenced in the second post on this thread is mainly applicable to CG not real footage. If this promo video you’re working on is CGI then it is worth every penny. If not, then you need to consider other postpro tricks (e.g. masks) to re-light the footage.

Yes, and the trick that I was trying to describe consists of applying that kind of manipulation in a very targeted manner. For instance, if you have a masking channel of information that tells you precisely where “Light #X” affects the shot and to what degree, you can construct a “noodle” that will exert a particular (say…) Color Balancing influence only upon those specific areas of the picture, and in just the right amounts. Limited only by your artistic creativity and your command of the Nodes system (and of the way of thinking that it promotes), you can do that at several different key points in “the mathematical production-line” that ultimately leads to “the finished picture.”

Think of it as the ultimate digital darkroom . . . Gone are the days of “dancing in the dark” in front of an enlarger, burning and dodging by hand, and yet, you’re doing the same thing for much the same reason, “as only a digital computer can do it.”

After spending a lot of hours testing and investigating over the weekend, I think that I succeeded to make a proper system in node editor for controlling lights with nodes.

System works if you do not have object with reflection and refraction materials. I do not know if it is poseble to control the colors in reflection and refraction. According to this tutorialis not.

I am attaching a blend file for those who want to test it.
With RGB input you control the color of the light and color of specular, with RGB curves you control enery/intensity of the light an specular. At the bottom are RGB and RGB curves nodes for controlling enviroment light.

Attachments

lights.blend (645 KB)