Program

class moderngl.Program

A Program object represents fully processed executable code in the OpenGL Shading Language, for one or more Shader stages.

In ModernGL, a Program object can be assigned to VertexArray objects. The VertexArray object is capable of binding the Program object once the VertexArray.render() or VertexArray.transform() is called.

Program objects has no method called use(), VertexArrays encapsulate this mechanism.

A Program object cannot be instantiated directly, it requires a context. Use Context.program() to create one.

Uniform buffers can be bound using Buffer.bind_to_uniform_block() or can be set individually. For more complex binding yielding higher performance consider using moderngl.Scope.

Create

Context.program(vertex_shader, fragment_shader=None, geometry_shader=None, tess_control_shader=None, tess_evaluation_shader=None, varyings=()) → Program

Create a Program object.

Only linked programs will be returned.

A single shader in the shaders parameter is also accepted. The varyings are only used when a transform program is created.

Parameters

  • shaders (list) – A list of Shader objects.

  • varyings (list) – A list of varying names.

Returns

Program object

Methods

Program.get(key, default) → Union[Uniform, UniformBlock, Subroutine, Attribute, Varying]

Returns a Uniform, UniformBlock, Subroutine, Attribute or Varying.

Parameters

default – This is the value to be returned in case key does not exist.

Returns

Uniform, UniformBlock, Subroutine, Attribute or Varying

Program.__getitem__(key) → Union[Uniform, UniformBlock, Subroutine, Attribute, Varying]

Get a member such as uniforms, uniform blocks, subroutines, attributes and varyings by name.

# Get a uniform
uniform = program['color']

# Uniform values can be set on the returned object
# or the `__setitem__` shortcut can be used.
program['color'].value = 1.0, 1.0, 1.0, 1.0

# Still when writing byte data we need to use the `write()` method
program['color'].write(buffer)
Program.__setitem__(key, value)

Set a value of uniform or uniform block

# Set a vec4 uniform
uniform['color'] = 1.0, 1.0, 1.0, 1.0

# Optionally we can store references to a member and set the value directly
uniform = program['color']
uniform.value = 1.0, 0.0, 0.0, 0.0

uniform = program['cameraMatrix']
uniform.write(camera_matrix)
Program.__iter__() → Generator[str, NoneType, NoneType]

Yields the internal members names as strings. This includes all members such as uniforms, attributes etc.

Example:

# Print member information
for name in program:
    member = program[name]
    print(name, type(member), member)

Output:

vert <class 'moderngl.program_members.attribute.Attribute'> <Attribute: 0>
vert_color <class 'moderngl.program_members.attribute.Attribute'> <Attribute: 1>
gl_InstanceID <class 'moderngl.program_members.attribute.Attribute'> <Attribute: -1>
rotation <class 'moderngl.program_members.uniform.Uniform'> <Uniform: 0>
scale <class 'moderngl.program_members.uniform.Uniform'> <Uniform: 1>

We can filter on member type if needed:

for name in prog:
    member = prog[name]
    if isinstance(member, moderngl.Uniform):
        print("Uniform", name, member)

or a less verbose version using dict comprehensions:

uniforms = {name: self.prog[name] for name in self.prog
            if isinstance(self.prog[name], moderngl.Uniform)}
print(uniforms)

Output:

{'rotation': <Uniform: 0>, 'scale': <Uniform: 1>}
Program.__eq__(other) → bool

Compares two programs opengl names (mglo).

Returns

If the programs have the same opengl name

Return type

bool

Example:

# True if the internal opengl name is the same
program_1 == program_2
Program.release()

Release the ModernGL object.

Attributes

Program.geometry_input

The geometry input primitive.

The GeometryShader’s input primitive if the GeometryShader exists. The geometry input primitive will be used for validation. (from layout(input_primitive) in;)

This can only be POINTS, LINES, LINES_ADJACENCY, TRIANGLES, TRIANGLE_ADJACENCY.

Type

int

Program.geometry_output

The geometry output primitive.

The GeometryShader’s output primitive if the GeometryShader exists. This can only be POINTS, LINE_STRIP and TRIANGLE_STRIP (from layout(output_primitive​, max_vertices = vert_count) out;)

Type

int

Program.geometry_vertices

The maximum number of vertices that

the geometry shader will output. (from layout(output_primitive​, max_vertices = vert_count) out;)

Type

int

Program.subroutines

The subroutine uniforms.

Type

tuple

Program.glo

The internal OpenGL object. This values is provided for debug purposes only.

Type

int

Program.mglo

Internal representation for debug purposes only.

Program.extra

Any - Attribute for storing user defined objects

Program.ctx

The context this object belongs to

Examples

A simple program designed for rendering

 1my_render_program = ctx.program(
 2    vertex_shader='''
 3        #version 330
 4
 5        in vec2 vert;
 6
 7        void main() {
 8            gl_Position = vec4(vert, 0.0, 1.0);
 9        }
10    ''',
11    fragment_shader='''
12        #version 330
13
14        out vec4 color;
15
16        void main() {
17            color = vec4(0.3, 0.5, 1.0, 1.0);
18        }
19    ''',
20)

A simple program designed for transforming

 1my_transform_program = ctx.program(
 2    vertex_shader='''
 3        #version 330
 4
 5        in vec4 vert;
 6        out float vert_length;
 7
 8        void main() {
 9            vert_length = length(vert);
10        }
11    ''',
12    varyings=['vert_length']
13)

Program Members