Modeling Attributes

Attributes are named values stored on vertices, points, primitives, and surfaces. Point color, position, UV coordinates , spline weight (W), and normal, for example, are stored as point attributes.

You can use the values of attributes in expressions to reshape, color, etc. points. For example, you could set the per-point color based on the vertical (Y) position of the point.

Some attributes (such as position) are automatically set by Houdini as you model the points, but you can also manually set attributes and add your own custom attributes.

The surface operators in the Attributes group of the tab menu exist to set different types of attributes. You can also set or create arbitrary attributes to particles using the Attribute SOP. This lets you store custom per-point information relevant to your model you can use later in expressions .

To see the attributes on the geometry in a node, press on the node’s tile in the network editor and choose Spreadsheet to open the geometry spreadsheet for the node.

Particles also have attributes, and attributes are very important when geometry and particle systems interact. For example, particles emitted from geometry inherit (by default) the attributes of the point from which they are emitted, and you can create interesting effects by transferring attributes between surfaces and particles using the Attribute Transfer POP.

The order of precedence for attributes from highest to lowest is:

• Vertex Attributes

• Point Attributes

• Primitive Attributes

• Detail Attributes

Attributes with a higher order of precedence override similar attributes with a lower order of precedence.