Long 4To Long 3Swizzle Driver component as seen in the Scene Inspector
Swizzle drivers are a type of component that allow for taking the components of a packed value (packed 3 or 4s) and rearrange them into the output. The different packed channels are numbered 0->2 for pack 3's and 0->3 for pack 4's. When driving the output, you have a choice of taking any channel within the pack 3 or 4 by number and driving an output channel with said source number. This can be used to flip axes, zero them out by using -1 as a source channel, or rearrange them. For example, making a 3d point move only on the y axis position of another point (-1, 1, -1).
