Hello guys.
A while ago I got stuck on the forum with a question someone made here about the blackbody node and the difference between its results and real light sources. That led me to a lot of research and with the help and patience of @joseph and @Okidoki I came up with some “tools” that I believe could be useful to many of us here.
These “tools” actually consist of a set of node groups developed to extend the possibility to apply the blackbody curve concept in other areas of Blender and have more control over the light in Blender.
The first node group consists of a substitute for the blackbody node from Blender. It works basically the same way, but instead of using a color chart sample image, as the blackbody node in Blender does (I don’t know why) it uses RGB curves and gives the possibility to work with color temperatures from 1000 K to 40000 k. Besides that, it has a normalized output and a simple raw RGB output. The normalized output works exactly as the blackbody node output does, but the RGB output gives the raw output of the RGB curve. That allows us to see the real color the light has instead of normalized to an intensity of 1.
The second node group called “white balance” is meant to be used in the compositor and works like the white balance of a photo camera. EX: if you use a light source with a color temperature of 2500 K its light would look orangeish unless you use this node group and adjust its color temperature to 2500 K. In this case, the light will look white. I know it’s possible to do it by hand and confide in our eyes, but I thought there was no point in creating physically accurate light sources to render an image and then using eyeballing to adjust the “camera” settings. The values you set there you can be sure are correct.
The third node group, “blackbody light groups”, is meant to be used also in the compositor, but with light groups. This node group allows you to deal with up to 9 different light groups. If you set all your lights on a scene to pure white (not using the blackbody node) you can then adjust all of them in the compositor using the node group as if you were using the blackbody node there. You can also change the intensity of the lights individually in this node group.
I hope this can be useful to someone as I believe it will.
Some examples:
Image rendered with lights with blackbody color temperature set at 3000k
The same render corrected in the compositor using the “white balance” node group
Image rendered with lights with blackbody color temperature set at 3000k
The same render corrected in the compositor using the “white balance” node group
Render made with white lights, no change
The same render using the “light groups” node group and setting different color temperatures individually
The same render changing light intensities in the compositor using the “light groups” node group
I hope you like it. Here is the blend file. If you have any questions, I know my English may be a bit confusing, but I would gladly try to help.
blackbody.blend (172.8 KB)
PS: I would also love to know your opinions.