Graphics Reference
In-Depth Information
Figure 9-66
Adding a Render Layers node
2.
The solid Curve objects in your 3D scene have alpha (opacity) values of 1.0. The background sky has
an alpha value of 0. By connecting the Alpha output socket of the Render Layers node to a Color input
socket of a Color Invert node (accessible from the Add menu by choosing Color > Invert) and checking
RGB, you convert this to a black and white color image with the garbage matte objects in black and the
background in solid white, as shown in
Figure 9-67
.
The solution now is simply a matter of multiplying the color values of the alpha-inverted black and white
garbage matte image and the original green screen matte you pulled previously. If these two mattes are multi-
plied together, only the areas where both mattes are white (that is, have 1 values) will be white. All other areas
will be multiplied by zero and so will turn out black.
1.
Add a Multiplication node by pressing Shift+A and choosing Color > Mix from the Add menu and
then selecting Multiply from the drop-down menu on the node.
2.
Make sure the Factor value is 1.0; then connect both mattes to this node's input sockets, and connect
the output socket of this node to the Composite node, as shown in
Figure 9-68
.
The resulting rendered
matte should look like
Figure 9-69
.
