The Connectivity SOP

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Connectivity

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This node adds a point or primitive attribute (default is called "class") and each piece of un-connected geometry is assigned a different number.  You can also use this to create a unique id for each uv island on a mesh.

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Summary:

    The connectivity node is really useful when you want to generate object IDs that are defined by connectivity or uv island.  Want to add variety to a shader by driving a signal that's unique to each object?  Or perhaps you're trying to inform a rbd solver which piece it needs to calculate separately via the "name" attribute.  There's plenty of situations where each piece of geometry needs a unique attribute value, and this node does that for you.

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Main Parameters:


Connectivity Type:


--  Would you like this attribute type to become a point or a primitive?  That is specified here.

Attribute:

--  What type of attribute would you like?  For more information about attribute types, please visit the attribute create node bible entry.  If you choose "string" then you'll need to also specify a prefix.

Local Variable:

--  This uses a legacy workflow which utilizes local variables (ex: $FOO) instead of attributes.  If you'd like to assign this connectivity data to a local variable, then that variable can be specified here.  In most situations, you don't need to concern yourself with this parameter.

Seam Group:

--  This is only available when using the "Primitive" connectivity type.  If you select some edges, this will separate out the geometry into a new section which receives a new attribute value.  See the below images for a visual explanation:
Use UV Connectivity:

--  When this is checked on, your UV islands will determine which sections receive a unique id

UV Attribute:


--  If you are utilizing uv sets with vertex attributes named something other than "uv" then you can specify that uv set name here.