Migration to V-Ray 3.0
Brute force path tracing optimizations
DOF and motion blur subdivs
Adaptive subdivision image sampler
V-Ray 3.0 adds a number of rendering optimization features. However for compatibility reasons, these features are automatically turned off when loading scenes saved with previous V-Ray versions. These features are listed below.
Max ray intensity - this parameter is disabled when loading old scenes, but is enabled by default for new scenes. See the Global switches section for more details.
Probabilistic lights - this feature is disabled for old scenes, but is enabled for newly created ones. See the Global switches section for more details.
Intel Embree - this feature is generally disabled by default and must be explicitly enabled both for old and new scenes. See the System section for more details.
The DMC system in V-Ray 3.0 has been modified to allow for more efficient brute force path tracing, especially where many GI bounces are used. In particular, V-Ray 3.0 makes much heavier use of a technique known as Russian roulette for probabilistic sampling of many material and lighting effects. This technique was also used in previous V-Ray versions, but V-Ray 3.0 makes a much more extensive use of it.
The Russian roulette technique may introduce some extra noise in the result, but allows many more samples to be computed. For this reason, some scenes may appear slightly noisier when rendered with V-Ray 3.0 compared to previous V-Ray versions and may need to be readjusted.
The subdivs parameters for depth of field and motion have been removed from the V-Ray UI (both in the main renderer and the physical camera), since the exact same effect can be achieved with adjusting the antialiasing settings. Scenes that use those parameters will need to be readjusted. The parameters are still accessible through MaxScript but do not have any effect.
The adaptive subvision sampler is still available for compatibility, but in general it is recommended to use one of the other image samplers (Fixed, Adaptive or Progressive). The adaptive subdivision sampler may be removed in future versions.