MtoA supports Maya particles and nparticles, however, there are some current limitations:

• Tube, Numeric, and Streak are not supported.
• There are some limitations with UV coordinates in particles and different textures (the Maya Ramp texture for example).
• The particle cloud shader is not supported.
• IPR refresh has to be forced from time to time.
• SSS is currently only supported for poly meshes.

A Maya scene that demonstrates nparticles rendered as volumes can be found here.

Interpolated Motion Blur

When the motion blur keys from the scene don't match the time where the nParticle cache was sampled, artifacts will appear. The Interpolated Motion Blur check will avoid this situation by using the nearest samples from the cache. This option requires that the nCache Evaluation Interval attribute be the same as the nCache Evaluate Every # frame(s) option that was used to create the nCache.

This option disables the rendering of particles that exceed the maximum particle Lifespan range when using motion blur.

^{Particles maximum lifespan range reaches poly plane (left). Delete Dead Particles: Off. Motion blur exceeds particle lifespan (incorrect)(center). Delete Dead Particles: On (correct motion blur)(right).}

Workflow Issues

Particle Sampler Info

MtoA does not export the particleSamplerInfo node. It exports some "userDataXXX" nodes and they require that the info is exported within the particles object.

The example below has a particleSamplerInfo connected to the Uv Co-ordinates of a ramp texture and the Out Uv Type is set to Normalized Age:

^{The particleSamplerInfo is ignored and the particles remain the same color over time}

By default, this will not work. However, it can be achieved by selecting the particleShape node, and in the Arnold section, in the Export Attributes, type 'age':

_{Adding 'Age' to the Arnold Export Attributes for the ParticleShape node fixes the connection to the ParticleSamplerInfo node}

A Maya scene file that demonstrates the above particle sampler info workflow can be found here.