Attribute format strings

An attribute format string specifies the format of a vertex attribute. Format strings are accepted by the create_attribute function as well as most methods in the pyglet.graphics module.

Format strings have the following (BNF) syntax:

attribute ::= ( name | index 'g' 'n'? ) count type

name describes the vertex attribute, and is one of the following constants for the predefined attributes:

c

Vertex color

e

Edge flag

f

Fog coordinate

n

Normal vector

s

Secondary color

t

Texture coordinate

v

Vertex coordinate

You can alternatively create a generic indexed vertex attribute by specifying its index in decimal followed by the constant g. For example, 0g specifies the generic vertex attribute with index 0. If the optional constant n is present after the g, the attribute is normalised to the range [0, 1] or [-1, 1] within the range of the data type.

count gives the number of data components in the attribute. For example, a 3D vertex position has a count of 3. Some attributes constrain the possible counts that can be used; for example, a normal vector must have a count of 3.

type gives the data type of each component of the attribute. The following types can be used:

b

GLbyte

B

GLubyte

s

GLshort

S

GLushort

i

GLint

I

GLuint

f

GLfloat

d

GLdouble

Some attributes constrain the possible data types; for example, normal vectors must use one of the signed data types. The use of some data types, while not illegal, may have severe performance concerns. For example, the use of GLdouble is discouraged, and colours should be specified with GLubyte.

Whitespace is prohibited within the format string.

Some examples follow:

v3f

3-float vertex position

c4b

4-byte colour

1eb

Edge flag

0g3f

3-float generic vertex attribute 0

1gn1i

Integer generic vertex attribute 1, normalized to [-1, 1]

2gn4B

4-byte generic vertex attribute 2, normalized to [0, 1] (because the type is unsigned)