material ID
Particle shapes can have various material IDs so that user can assign various materials through the Multi/Sub-Object Material.
[Inputs]
#Particle Stream - This pin requires a particle stream to be connected. Connection is usually not required if any of the attributes is connected.
Enabled - Enable or disable node evaluation.
Write to Shape - If the particle shape is a mesh instance, this node cannot directly write new face Material IDs, as instanced geometry is shared among many particles. However, it will use a Material ID for the entire particle shape and pass it to renderers that support per-particle Material ID override (it is a part of the standard 3ds max API), such as Arnold and FStorm.
Shift Multi MtlIDs ??? This option is available if "Write to Shape" is enabled and allows users to shift current face material ID(s). In an object with multiple Material IDs, this will be the index of the first Material ID, with the others shifted accordingly.
Material ID - This setting allows you to assign a Material ID to a particle and/or its shape. For shape instances, this option enables the use of different Material IDs for each particle shape. For other shapes that are not instances and have multiple Material IDs, these will be overwritten unless the "Shift Multi MtlIDs" option is enabled. If "Write to Shape" is enabled, only the face-based Material IDs will be written, while the particle's Material ID will remain unchanged.