Variables¶

Variables are entry points in the shader that allow to upload CPU data to the GPU. For OpenGL ES 2.0, there are mainly two types: uniforms and attributes. The correspondance betwenn GPU and CPU data types is given in the table below.

GLSL Type	GLSL/GL Type	#	GL elementary type	Numpy type
float	gl.GL_FLOAT	1	gl.GL_FLOAT	np.float32
vec2	gl.GL_FLOAT_VEC2	2	gl.GL_FLOAT	np.float32
vec3	gl.GL_FLOAT_VEC3	3	gl.GL_FLOAT	np.float32
vec4	gl.GL_FLOAT_VEC4	4	gl.GL_FLOAT	np.float32
int	gl.GL_INT	1	gl.GL_INT	np.int32
ivec2	gl.GL_INT_VEC2	2	gl.GL_INT	np.int32
ivec3	gl.GL_INT_VEC3	3	gl.GL_INT	np.int32
ivec4	gl.GL_INT_VEC4	4	gl.GL_INT	np.int32
bool	gl.GL_BOOL	1	gl.GL_BOOL	np.bool
bvec2	gl.GL_BOOL_VEC2	2	gl.GL_BOOL	np.bool
bvec3	gl.GL_BOOL_VEC3	3	gl.GL_BOOL	np.bool
bvec4	gl.GL_BOOL_VEC4	4	gl.GL_BOOL	np.bool
mat2	gl.GL_FLOAT_MAT2	4	gl.GL_FLOAT	np.float32
mat3	gl.GL_FLOAT_MAT3	9	gl.GL_FLOAT	np.float32
mat4	gl.GL_FLOAT_MAT4	16	gl.GL_FLOAT	np.float32
sampler1D	gl.GL_SAMPLER_1D	1	gl.GL_UNSIGNED_INT	np.uint32
sampler2D	gl.GL_SAMPLER_2D	1	gl.GL_UNSIGNED_INT	np.uint32
samplerCube	gl.GL_SAMPLER_CUBE	1	gl.GL_UNSIGNED_INT	np.uint32

Note

Most of the time, you don’t need to directly manipulate such variables since they are created automatically when shader code is parsed.

Example usage

vertex = '''
    attribute vec3 position;
    void main (void)
    {
        gl_Position = vec4(position, 1.0);
    } '''
fragment = '''
    uniform vec4 color;
    void main(void)
    {
        gl_FragColor = color;
    } '''
program = gloo.Program(vertex, fragment, count=4)
# program["position"] type is Attribute
# program["color"] type is Uniform

Content

Variable — Generic variable methods
Uniform — Uniform variable
Attribute — Attribute variable
Uniforms — Group of uniforms

Variable¶

class glumpy.gloo.Variable(program, name, gtype)¶

Bases: glumpy.gloo.globject.GLObject

A variable is an interface between a program and data

active¶: Whether this variable is active in the program

data¶: CPU data

dtype¶: Equivalent dtype of the variable

gtype¶: Type of the underlying variable (as a GL constant)

name¶: Variable name

program¶: Program this variable belongs to

Uniform¶

class glumpy.gloo.Uniform(program, name, gtype)¶

Bases: glumpy.gloo.variable.Variable

A Uniform represents a program uniform variable.

set_data(data)¶: Assign new data to the variable (deferred operation)

Attribute¶

class glumpy.gloo.Attribute(program, name, gtype)¶

Bases: glumpy.gloo.variable.Variable

An Attribute represents a program attribute variable

set_data(data)¶: Assign new data to the variable (deferred operation)

size¶: Size of the underlying vertex buffer

Uniforms¶

class glumpy.gloo.Uniforms(size, dtype)¶

Bases: glumpy.gloo.texture.Texture2D

Uniforms data texture holder.

This class is used in conjunction with collections in order to store a number of uniforms in a texture such that each vertices can retrieve a specific group of uniforms. The data type can be structured but must be reduceable to n x np.float32. Note that you don’t need to manipulate directly this function, it is done automagically in collections.

Note

The code needed to retrieve a specific item is given from the code function and is generated specifically for the actual data type.

Parameters:	size (int) – Number of items to be stored in the texture dtype (numpy.dtype) – Item data type (must be reduceable to n x np.float32)

code(prefix='u_')¶: Generate the GLSL code needed to retrieve fake uniform values from a texture. The generated uniform names can be prefixed with the given prefix.