Attribute

Attributes are data associated with POP (or SOP) geometry. Points, Vertex (Vertices)s and Primitives (polygons, lines, etc) can have any number of attributes. In POPs, position (P) is standard, and built-in optional attributes are normals (N), texture coordinates (Tex), color (Color), etc.

For attributes of SOPs see SOP Attribute as this page is being re-focused on POPs (in-progress).

A point attribute is a named set of numbers, one for each point of a POP. A scalar point attribute is a single number for each point. A vector point attribute is 2, 3 or 4 numbers per point, such as the P (position) attribute which is a float3 (3-number) vector attribute.

A primitive attribute is a named set of numbers, one for each primitive of a POP. A scalar primitive attribute is a single number for each primitive. A vector primitive attribute is 2, 3 or 4 numbers per primitive.

A vertex attribute is a named set of numbers, one for each vertex of each primitive of a POP. A scalar vertex attribute is a single number for each vertex. A vector vertex attribute is 2, 3 or 4 numbers per vertex.

Attribute Terminolgyedit

• Built-in Attributes - Attributes that are strictly reserved, like P, PointScale, N and Tex.
• Common Attributes - Attributes that are commonly used but not strictly controlled by TouchDesigner, like PartMass and PartVel.
• Read-Only Attributes - attributes that are pre-computed by TouchDesigner (like normalized point number _PointU) that can be used in Math POP. Math Mix, Math Combine POPs and others.
• Components of Attributes - For attributes that are vectors, a flaot3 has 3 "components".
• Attribute Class - refers to Point, Vertex and Primitive classes.
• Array Attribute - an attribute type that has per-point multiple float or float2 etc
• Scalar Attribute vs Vector Attribute

Common Attributesedit

Normals (N)edit

See Normals. A normal is a directional vector associated with a particular geometric entity, commonly perpendicular to it. The normal to a surface at a given point is a vector perpendicular to the surface at that point, and is computed as the cross product of the tangent vectors at that point.

Color (Color)edit

Surface color and alpha specified by RGBA. Values range from 0 to 1. The alpha component Color.a controls the transparency of a given element, where 1 is fully opaque, and 0 is fully transparent.

Texture Coordinates (Tex)edit

Items are located spatially by XYZ values. To differentiate texture coordinate space from XYZ space, the labels U and V and sometimes W are used instead of X and Y and Z. ​ In order to place texture maps (images) onto geometry, we must assign texture coordinates to the geometry. A texture map resides in its own (U, V) texture coordinate space. When assigned to the geometry, the (U, V) coordinates determine how to map the image onto the geometry, where U,V of 0,0 uses the bottom left of the texture image, and 1,1 use the top-right. ​ Most generator POPs like Sphere POP and Plane POP have texture coordinates already assigned to each point or vertex. ​ Texture coordinates can be visualized in the following manner: Texture maps have their own coordinate space. If the texture were a table cloth with a grid pattern, the color at location 3, 4 on the table cloth remains at location 3, 4 even when the cloth is wrapped around an irregularly shaped object. The color at location 3, 4 can be said to be in the table-cloth's coordinate space. ​

Order of Attribute Precedenceedit

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

1. Vertex Attributes
2. Point Attributes
3. Primitive Attributes

Attributes with a higher order of precedence override the same attributes with a lower order of precedence. (Only the Bone Group SOP has Detail attributes from skeletons imported externally.)

Point and vertex attributes are interpolated across primitives, allowing more local flexibility than primitive attributes (e.g. Color). Vertex attributes deal with the situation where shared points need different values for the attributes at the boundary of primitives, like the longitudinal seam of a polar texture map for example. Primitive colors typically take us less memory point colors, and point colors less than vertex colors.

Custom Attributesedit

Below are the Attributes which are currently reserved for TouchDesigner use.

Point Attributesedit

Point Attributes are Attributes on Points in a POP.

Vertex Attributesedit

A Triangle, Quadrelateral or Line Strip is made of a set of Vertices, and each Vertex refers to a Point.

Primitive Attributesedit

You can use the Primitive SOP or the SOP to DAT and DAT to SOP pair to add or modify primitive attributes.

plus Force dir, fedge, fvortex, fspiral xxx

Data Types of Attributesedit

There are three different attribute data types. Each is handled slightly differently internally.