Close

Attribute


Attributes include information about an entity such as its color, velocity, normal, and so on. Attributes can be attached to Vertices, Points, Primitives, or the whole geometry.

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 seam of a polar texture map for example. Primitive colors typically take us less memory point colors, and point colors less than vertex colors.

See also: Point List, Geometry Detail, Point Class, Primitive, Polygon, Vertex, Prims Class, SOP, SOP Class, Point SOP, Attribute SOP, Attribute Create SOP, SOP to DAT, Script SOP, Point Groups, Primitive Groups.

Common Attributes

Normals

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.

Colors

Surface color and alpha specified by RGBA. Values range from 0 to 1. The alpha component Cd(3) controls the transparency of a given element, where 1 is fully opaque, and 0 is fully transparent.

Texture Coordinates (UV)

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. Texture space should not be mistaken for the parametric space of splines. ​ Generators SOPs like Sphere SOP and Grid SOP have UVs already assigned to each point. The Texture SOP, Point SOP or the SOP to DAT with the DAT to SOP pairs to add or modify the attributes. ​ 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. ​ TIP: By using a Point SOP, you can swap the position and the texture coordinates. This allows you to model the "texture space". Another Point SOP allows you to swap the position and texture back to their original locations.

Order of Attribute Precedence

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

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

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

Custom Attributes

Below are the Attributes which are currently reserved for TouchDesigner use. In addition the user can create any number of custom attributes on SOPs using the Point SOP, Vertex SOP and Primitive SOP.


Point Attributes

Point Attributes are Attributes on Points in a SOP. The Point SOP can create most of these attributes.

Name Type Size Description SOP to Create SOP where Used Notes
P float 3 Point position
Pw float 1 Point weight
N vector 3 Surface Normal Facet SOP
uv float 3 Texture Coordinates Texture SOP
Cd float 4 Surface color and alpha
pCapt float 2 Capture data for Deform contains index and weight for a transform. See Deforming Geometry (Skinning)
v vector 3 Velocity often taken from Normal
mass float 1 Mass Particle SOP, Spring SOP
drag float 1 Drag Particle SOP, Spring SOP
life float 1 Life Expectancy Particle SOP
age float 1 Age Particle SOP
id float 1 Particle Identifying Tag Particle SOP
rest vector 3 Rest Position
tension float 1 Tension
springk float 1 Spring constant Spring SOP
up vector 3 Up
pscale float 1 Particle scale
radiusf xxx float 1 Radius
fscalef xxx float 1 Force scale
fradial float 1 Radial force
normalf xxxx float 1 Normal force
fedge float 1 Edge force
edge_dir vector 3 Edge direction
dir vector 3 Directional force

Vertex Attributes

A Polygon is made of a set of Vertices, and each Vertex refers to a Point. You can use the Vertex SOP to create vertex attributes. The SOP to DAT and DAT to SOP pair can create and modify vertex attributes.

Name Type Size Description SOP to Create SOP where Used Notes
N vector 3 Surface normal Facet SOP, Attribute Create SOP
uv float 3 Texture coordinates Texture SOP
Cd float 4 Surface color and alpha
creaseweight float 1 Crease weights used in sub-division surfaces. See Subdivide SOP.
T float 4 Tangents Attribute Create SOP two 2D vectors = 4 values
pCapt float 2 Capture data contains index and weight for a transform. See Deforming Geometry (Skinning)

Primitive Attributes

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

Name Type Size Description SOP to Create SOP where Used Notes
N vector 3 Surface normal
Cd float 4 Surface color and alpha
creaseweight float 1 Crease weights used in sub-division surfaces. See Subdivide SOP.
mat index 1 Material Material SOP

plus Force dir, fedge, fvortex, fspiral xxx

Detail Attributes

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

Name Type Size Description SOP to Create SOP where Used Notes
mat index 1 Material Material SOP
bone float 1 Bone Info for deforming, with imported 3D objects.
creaseweight float 1 Crease weights used in sub-division surfaces. See Subdivide SOP.

Data Types of Attributes

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

Vector Data This data type represents a 3D vector in space. When any transforms occur on the detail, this attribute will also be transformed. Examples of a vector attribute are normals (N) or velocity (v).
Floating Point Data This data type represents an array of floating point values. The values are not transformed when the geometry gets transformed. Some examples of this type of attribute are diffuse colors (Cd), and texture co-ordinates (uv).
Indexed String Data This attribute consists of an ordered list of character strings. The attribute stored with the element is an integer representing the offset into the array of strings. A value outside the bounds of the array is considered to be "not assigned". An example of this is the material attribute.


See also: Geometry Detail, Point, Point List, Point Class, Primitive, Prims Class, Polygon, Vertex, SOP, SOP Class, Script SOP, Point Groups, Primitive Groups.