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From Odwiki

What is it?

Attribute Create SOP allows you to create (or declare) an attribute. Any attributes that is created with this SOP will also have a local variable mapping for easy access for the rest of the chain.

What is an Attribute?

Attributes in Houdini are simply variables that store numerical or string values. It is also one of the vital abilities of Houdini to be able to easily pass data around in the form of attribute. Houdini has four different types of attribute, as explained in the following.

Point Attributes are those that stored onto every point of the incoming geometry. Obviously, storing attribute onto every single point consumes a little more memory than other attribute type. Where Houdini calls it "point", other software packages may call it "vertex". A single point in Houdini can be shared by other connecting primitive.

Primitive Attributes are those that stored, well, onto every primitive. Each of these primitives in Houdini can be thought of as a single polygon or a spline patch if you're not as familiar with Houdini jargon. For example, if we have a polygon cube that contain six primitives (or polygons) with 8 points. There would be total of six primitive attributes (as oppose to eight). Obviously, this means Primitive Attribute is lighter on memory footprint.

Vertex Attributes are those that are often stored for texture on the vertex. Unlike Point, vertices of one primitive in Houdini are not shared by other primitives.

Detail Attributes are those that are stored for the whole geometry, and thus has the lightest memory footprint. Regardless of point or primitive count, there will only be one Detail Attribute of that name. Even though Detail attribute isn't as often used, they can play a big role in studios that require Houdini geometry to fit into a specific pipeline, as if applying a tag to geometry. Local variable mapping is stored as a Detail attribute.

For more information: GeometryAttributes

Back to: SOPs