Function: channelEffectiveType()
channelEffectiveType(
channel):string
Resolves a channel descriptor's effective type label - its explicit
type if it set one, otherwise a generic size-based default ('float',
'float2', 'float3') so every channel (built-in or caller-supplied) has
some type label to key off of without forcing every descriptor to state
the obvious.
Parameters
channel
Returns
string