The V-Ray Multi-Sub Tex texture distributes multiple textures to many objects via one single material based on specified IDs or random distribution.

In the image shown here, Multi-Sub Tex's Get ID from parameter has its type set to Object ID. Each part of the ball is assigned a texture. The Multi-Sub Tex is then assigned to the diffuse channel of a single V-Ray Material.

See the Randomization Options page or the Courseware page for more information.

Default Color – Allows the user to assign a color or texture. When a texture is selected, it overrides the color as long as the texture checkbox is enabled.

Get ID from – Specifies the meaning of the ID parameters.

Use Face Material ID – When more than one material is applied to the different faces of the same object, V-Ray for Rhino internally creates face IDs. If all those materials share the same Multi-Sub texture, V-Ray considers the face IDs when feeding the data (color or texture) to the materials.
Note that faces inheriting such a material applied to the group instead will use ID 0. Faces with IDs that do not have a corresponding sub-color/texture use the Default Color.
Use Object ID – The Multi-Sub texture considers the Object IDs of the object when feeding the data (color or texture) to the material.

Loop Textures – When this option is enabled and the number of shaded IDs exceeds the number of IDs in this texture, the geometry IDs are wrapped to fit the available range.

Random:

By Node Handle – Each node is assigned a unique number (or, "handle") when it is created. This option generates the color index based on that node ID. It is useful because the node handle survives through scene editing. For example, if an object is added, removed, or renamed, the colors remain the same.
By Node Name – Generates a color index based on the name of the node that the texture is applied to.
By Face Material ID – Face Material IDs are differentiated when multiple materials are assigned to the faces of a single mesh.
By Mesh Element – A mesh element is considered each island of connected mesh faces.
By Render ID – The Render ID is an object identifier assigned during Render time.
By Instance ID – Instances are considered objects copied by V-Ray Scatter or instances from a referenced alembic abc file loaded as a Mesh Proxy.
By Object ID – Object IDs can be manually defined for each scene object.

Hue/Saturation/Gamma Variation – Active when the Get ID from parameter is set to some of the Random options. These three parameters control post-process randomization of output color. The input value is the percentage of the HSV/gamma range and specifies the maximum random deviation, where the gamma range is fixed to [1/10,10]. See the Random Hue/Sat/Gamma example below.

Seed – Changes the randomization pattern.

Add Texture – Adds a new sub-texture to the texture list.

Used – This checkbox enables the sub-texture for rendering.

Value – For modes that use IDs, this value specifies the ID that corresponds to each texture.