Graphics Reference
In-Depth Information
Figure 9-42
Viewing the individual color channels
As you'd expect, the highest-contrast channel is the green channel, which has a high-intensity background
thankstothegreenscreen.Theredchannel,ontheotherhand,ismuchmoreuniformlydistributed.Theprocess
of pulling a green screen matte depends on this difference in intensity ranges between the green and red chan-
nels.
Nowyoucanusethedifferenceinchannelintensities topullthematteitself.Blender'snodesystemincludes
specificnodesforcreatingmattesinfewersteps,butinordertounderstandexactlywhatishappening,itisgood
to do it yourself by hand. Also, walking through the process will make the subsequent garbage-matting step
easier to understand. The idea here is to subtract the red channel of the image from the green channel by using
a Subtract node.
