RIRE, the OSL Path Tracer: some improvements

RIRE, our full OSL Path Tracer 'pour rire', is going on !

The last improvements are :
- Better Russian Roulette (still need more improvements).
- Shortest Path evalutation, with Back Directionnal Path Tracing.
- Better mixing between direct light and environment contribution.

Now, some comparisons with Cycles, even if comparaison is not reason ! RIRE is about 30 to 40% slower. Indeed, it's faster than expected !

Comparaison : 200 Samples, 64 bounces max :
RIRE :

Cycles :

Now, with just 20 Samples! :
RIRE :

Cycles :

And just some test render :

To be continued!