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#