Minor fixes
Minor fix
Proper return value in GeometricPrimitive.intersect()
Proper isinstance() call ordering
New class: Material
New class: UberMaterial
Returned values were assigned to wrong variables
Mirroring example scene from pbrt
Added a variable to hold the aggregate
Fixed the perspective camera initialization (wrong frame values)
Added missing import
Changed default number of samples for the random sampler
Merge branch 'master' of github.com:big--ben/pyPbrt