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: str, fragment_shader: Optional[str] = None, geometry_shader: Optional[str] = None, tess_control_shader: Optional[str] = None, tess_evaluation_shader: Optional[str] = None, varyings: Tuple[str, ...] = (), fragment_outputs: Optional[Dict[str, int]] = None, varyings_capture_mode: str = 'interleaved') → Program

Create a Program object.

The varyings are only used when a transform program is created to specify the names of the output varyings to capture in the output buffer.

fragment_outputs can be used to programmatically map named fragment shader outputs to a framebuffer attachment numbers. This can also be done by using layout(location=N) in the fragment shader.

Parameters

vertex_shader (str) – The vertex shader source.
fragment_shader (str) – The fragment shader source.
geometry_shader (str) – The geometry shader source.
tess_control_shader (str) – The tessellation control shader source.
tess_evaluation_shader (str) – The tessellation evaluation shader source.
varyings (list) – A list of varyings.
fragment_outputs (dict) – A dictionary of fragment outputs.

Returns

Program object

Methods

Program.get(key: str, default: Any) → 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: str) → 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: str, value: Any) → None

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, None, None]

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: Any) → 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() → None: 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.is_transform

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

Type: bool

Program.ctx: The context this object belongs to

Examples

A simple program designed for rendering

my_render_program = ctx.program(
    vertex_shader='''
        #version 330

        in vec2 vert;

        void main() {
            gl_Position = vec4(vert, 0.0, 1.0);
        }
    ''',
    fragment_shader='''
        #version 330

        out vec4 color;

        void main() {
            color = vec4(0.3, 0.5, 1.0, 1.0);
        }
    ''',
)

A simple program designed for transforming

my_transform_program = ctx.program(
    vertex_shader='''
        #version 330

        in vec4 vert;
        out float vert_length;

        void main() {
            vert_length = length(vert);
        }
    ''',
    varyings=['vert_length']
)

Program

Create

Methods

Attributes

Examples

Program Members