This function is optimized for when you need a quick RenderTexture to do some temporary calculations.
Release it using
ReleaseTemporary as soon as you're done with it, so another call can
start reusing it if needed.
Internally Unity keeps a pool of temporary render textures, so a call to GetTemporary most often
just returns an already created one (if the size and format matches). These temporary render textures
are actually destroyed when they aren't used for a couple of frames.
If you are doing a series of post-processing "blits", it's best for performance to get and release
a temporary render texture for each blit, instead of getting one or two render textures upfront and reusing
them. This is mostly beneficial for mobile (tile-based) and multi-GPU systems: GetTemporary will internally
do a
DiscardContents call which helps to avoid costly restore operations on the previous
render texture contents.
You can not depend on any particular contents of the RenderTexture you get from GetTemporary function.
It might be garbage, or it might be cleared to some color, depending on the platform.