Program

class Program

Returned by Context.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.

Methods

Program.get(key: str, default: Any) Uniform | UniformBlock | Attribute | Varying

Returns a Uniform, UniformBlock, Attribute or Varying.

Parameters:

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

Program.__getitem__()

Get a member such as uniforms, uniform blocks, 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__()

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__()

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.release() None

Release the ModernGL object.

Attributes

Program.geometry_input: int

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.

Program.geometry_output: int

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;)

Program.geometry_vertices: int

The maximum number of vertices that the geometry shader will output. (from layout(output_primitive, max_vertices = vert_count) out;)

Program.is_transform: int

If this is a tranform program (no fragment shader).

Program.ctx: Context

The context this object belongs to

Program.glo: int

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

Program.extra: Any

User defined data.

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