[Bf-cycles] Random values in SVM nodes

[Lukas Stockner]

Hi all,
I recently noticed that a Random Value Node would be useful, for example 
for spectral dispersion shader setups.
So now I'm thinking about implementing one, but my question is how to do 
the actual random number generation in the SVM. Using the randb value 
will probably give correlation issues, so the best approach would be to 
actually get a separate number from the RNG. However, since the number 
of random nodes used isn't known in advance, so setting aside RNG 
dimensions for these is problematic (also, allocating several dimensions 
per bounce only for the nodes is quite a waste since it reduces quality 
for the other values).
So far, my best idea was to hash the randb value and use the resulting 
value as a seed for a LCG, however, for this every Random Node would 
have to carry an unique ID. However, the resulting samples wouldn't be 
as well-distributed as regular RNG samples...
So, do you think the hashing idea would work, would you use another 
approach or not add a Random Node at all?

Lukas Stockner