QOpenGLShaderProgram¶

PyQt5.QtGui.QOpenGLShaderProgram: Inherits from QObject.

Description¶

The QOpenGLShaderProgram class allows OpenGL shader programs to be linked and used.

Introduction¶

This class supports shader programs written in the OpenGL Shading Language (GLSL) and in the OpenGL/ES Shading Language (GLSL/ES).

QOpenGLShader and QOpenGLShaderProgram shelter the programmer from the details of compiling and linking vertex and fragment shaders.

The following example creates a vertex shader program using the supplied source code. Once compiled and linked, the shader program is activated in the current QOpenGLContext by calling bind():

# QOpenGLShader shader(QOpenGLShader::Vertex);
# shader.compileSourceCode(code);

# QOpenGLShaderProgram program(context);
# program.addShader(&shader);
# program.link();

# program.bind();

Writing Portable Shaders¶

Shader programs can be difficult to reuse across OpenGL implementations because of varying levels of support for standard vertex attributes and uniform variables. In particular, GLSL/ES lacks all of the standard variables that are present on desktop OpenGL systems: gl_Vertex, gl_Normal, gl_Color, and so on. Desktop OpenGL lacks the variable qualifiers highp, mediump, and lowp.

The QOpenGLShaderProgram class makes the process of writing portable shaders easier by prefixing all shader programs with the following lines on desktop OpenGL:

#define highp
#define mediump
#define lowp

This makes it possible to run most GLSL/ES shader programs on desktop systems. The programmer should restrict themselves to just features that are present in GLSL/ES, and avoid standard variable names that only work on the desktop.

Simple Shader Example¶

# program.addShaderFromSourceCode(QOpenGLShader::Vertex,
#     "attribute highp vec4 vertex;\n"
#     "uniform highp mat4 matrix;\n"
#     "void main(void)\n"
#     "{\n"
#     "   gl_Position = matrix * vertex;\n"
#     "}");
# program.addShaderFromSourceCode(QOpenGLShader::Fragment,
#     "uniform mediump vec4 color;\n"
#     "void main(void)\n"
#     "{\n"
#     "   gl_FragColor = color;\n"
#     "}");
# program.link();
# program.bind();

# int vertexLocation = program.attributeLocation("vertex");
# int matrixLocation = program.uniformLocation("matrix");
# int colorLocation = program.uniformLocation("color");

With the above shader program active, we can draw a green triangle as follows:

# static GLfloat const triangleVertices[] = {
#     60.0f,  10.0f,  0.0f,
#     110.0f, 110.0f, 0.0f,
#     10.0f,  110.0f, 0.0f
# };

# QColor color(0, 255, 0, 255);

# QMatrix4x4 pmvMatrix;
# pmvMatrix.ortho(rect());

# program.enableAttributeArray(vertexLocation);
# program.setAttributeArray(vertexLocation, triangleVertices, 3);
# program.setUniformValue(matrixLocation, pmvMatrix);
# program.setUniformValue(colorLocation, color);

# glDrawArrays(GL_TRIANGLES, 0, 3);

# program.disableAttributeArray(vertexLocation);

Binary Shaders and Programs¶

Binary shaders may be specified using glShaderBinary() on the return value from shaderId(). The QOpenGLShader instance containing the binary can then be added to the shader program with addShader() and linked in the usual fashion with link().

Binary programs may be specified using glProgramBinaryOES() on the return value from programId(). Then the application should call link(), which will notice that the program has already been specified and linked, allowing other operations to be performed on the shader program. The shader program’s id can be explicitly created using the create() function.

Caching Program Binaries¶

As of Qt 5.9, support for caching program binaries on disk is built in. To enable this, switch to using addCacheableShaderFromSourceCode() and addCacheableShaderFromSourceFile(). With an OpenGL ES 3.x context or support for GL_ARB_get_program_binary, this will transparently cache program binaries under GenericCacheLocation or CacheLocation. When support is not available, calling the cacheable function variants is equivalent to the normal ones.

Note: Some drivers do not have any binary formats available, even though they advertise the extension or offer OpenGL ES 3.0. In this case program binary support will be disabled.

See also

QOpenGLShader.

Methods¶

__init__(parent: QObject = None)

Constructs a new shader program and attaches it to parent. The program will be invalid until addShader() is called.

The shader program will be associated with the current QOpenGLContext.

See also

addShader().

addCacheableShaderFromSourceCode(Union[ShaderType, ShaderTypeBit], Union[QByteArray, bytes, bytearray]) → bool

This is an overloaded function.

Registers the shader of the specified type and source to this program. Unlike addShaderFromSourceCode(), this function does not perform compilation. Compilation is deferred to link(), and may not happen at all, because link() may potentially use a program binary from Qt’s shader disk cache. This will typically lead to a significant increase in performance.

Returns true if the shader has been registered or, in the non-cached case, compiled successfully; false if there was an error. The compilation error messages can be retrieved via log().

When the disk cache is disabled, via Qt::AA_DisableShaderDiskCache for example, or the OpenGL context has no support for context binaries, calling this function is equivalent to addShaderFromSourceCode().

addCacheableShaderFromSourceCode(Union[ShaderType, ShaderTypeBit], str) → bool

This is an overloaded function.

Registers the shader of the specified type and source to this program. Unlike addShaderFromSourceCode(), this function does not perform compilation. Compilation is deferred to link(), and may not happen at all, because link() may potentially use a program binary from Qt’s shader disk cache. This will typically lead to a significant increase in performance.

When the disk cache is disabled, via Qt::AA_DisableShaderDiskCache for example, or the OpenGL context has no support for context binaries, calling this function is equivalent to addShaderFromSourceCode().

addCacheableShaderFromSourceFile(Union[ShaderType, ShaderTypeBit], str) → bool

Registers the shader of the specified type and fileName to this program. Unlike addShaderFromSourceFile(), this function does not perform compilation. Compilation is deferred to link(), and may not happen at all, because link() may potentially use a program binary from Qt’s shader disk cache. This will typically lead to a significant increase in performance.

Returns true if the file has been read successfully, false if the file could not be opened or the normal, non-cached compilation of the shader has failed. The compilation error messages can be retrieved via log().

When the disk cache is disabled, via Qt::AA_DisableShaderDiskCache for example, or the OpenGL context has no support for context binaries, calling this function is equivalent to addShaderFromSourceFile().

addShader(QOpenGLShader) → bool

Adds a compiled shader to this shader program. Returns true if the shader could be added, or false otherwise.

Ownership of the shader object remains with the caller. It will not be deleted when this QOpenGLShaderProgram instance is deleted. This allows the caller to add the same shader to multiple shader programs.

addShaderFromSourceCode(Union[ShaderType, ShaderTypeBit], Union[QByteArray, bytes, bytearray]) → bool

This is an overloaded function.

Compiles source as a shader of the specified type and adds it to this shader program. Returns true if compilation was successful, false otherwise. The compilation errors and warnings will be made available via log().

This function is intended to be a short-cut for quickly adding vertex and fragment shaders to a shader program without creating an instance of QOpenGLShader first.

addShaderFromSourceCode(Union[ShaderType, ShaderTypeBit], str) → bool

This is an overloaded function.

Compiles source as a shader of the specified type and adds it to this shader program. Returns true if compilation was successful, false otherwise. The compilation errors and warnings will be made available via log().

This function is intended to be a short-cut for quickly adding vertex and fragment shaders to a shader program without creating an instance of QOpenGLShader first.

addShaderFromSourceFile(Union[ShaderType, ShaderTypeBit], str) → bool

Compiles the contents of fileName as a shader of the specified type and adds it to this shader program. Returns true if compilation was successful, false otherwise. The compilation errors and warnings will be made available via log().

This function is intended to be a short-cut for quickly adding vertex and fragment shaders to a shader program without creating an instance of QOpenGLShader first.

See also

addShader(), addShaderFromSourceCode().

attributeLocation(Union[QByteArray, bytes, bytearray]) → int

This is an overloaded function.

Returns the location of the attribute name within this shader program’s parameter list. Returns -1 if name is not a valid attribute for this shader program.

attributeLocation(str) → int

This is an overloaded function.

Returns the location of the attribute name within this shader program’s parameter list. Returns -1 if name is not a valid attribute for this shader program.

bind() → bool: Binds this shader program to the active QOpenGLContext and makes it the current shader program. Any previously bound shader program is released. This is equivalent to calling glUseProgram() on programId(). Returns true if the program was successfully bound; false otherwise. If the shader program has not yet been linked, or it needs to be re-linked, this function will call link().

See also

link(), release().

bindAttributeLocation(Union[QByteArray, bytes, bytearray], int)

This is an overloaded function.

Binds the attribute name to the specified location. This function can be called before or after the program has been linked. Any attributes that have not been explicitly bound when the program is linked will be assigned locations automatically.

When this function is called after the program has been linked, the program will need to be relinked for the change to take effect.

See also

attributeLocation().

bindAttributeLocation(str, int)

This is an overloaded function.

Binds the attribute name to the specified location. This function can be called before or after the program has been linked. Any attributes that have not been explicitly bound when the program is linked will be assigned locations automatically.

When this function is called after the program has been linked, the program will need to be relinked for the change to take effect.

See also

attributeLocation().

create() → bool

Requests the shader program’s id to be created immediately. Returns true if successful; false otherwise.

This function is primarily useful when combining QOpenGLShaderProgram with other OpenGL functions that operate directly on the shader program id, like GL_OES_get_program_binary.

When the shader program is used normally, the shader program’s id will be created on demand.

See also

programId().

defaultInnerTessellationLevels() → List[float]

Returns the default inner tessellation levels to be used by the tessellation primitive generator in the event that the tessellation control shader does not output them. For more details on OpenGL and Tessellation shaders see OpenGL Tessellation Shaders.

Returns a QVector of floats describing the inner tessellation levels. The vector will always have two elements but not all of them make sense for every mode of tessellation.

Note: This returns the global OpenGL state value. It is not specific to this QOpenGLShaderProgram instance.

Note: This function is only supported with OpenGL >= 4.0 and will not return valid results with OpenGL ES 3.2.

defaultOuterTessellationLevels() → List[float]

Returns the default outer tessellation levels to be used by the tessellation primitive generator in the event that the tessellation control shader does not output them. For more details on OpenGL and Tessellation shaders see OpenGL Tessellation Shaders.

Returns a QVector of floats describing the outer tessellation levels. The vector will always have four elements but not all of them make sense for every mode of tessellation.

Note: This returns the global OpenGL state value. It is not specific to this QOpenGLShaderProgram instance.

Note: This function is only supported with OpenGL >= 4.0 and will not return valid results with OpenGL ES 3.2.

disableAttributeArray(int): Disables the vertex array at location in this shader program that was enabled by a previous call to enableAttributeArray().

See also

enableAttributeArray(), setAttributeArray(), setAttributeValue(), setUniformValue().

disableAttributeArray(str)

This is an overloaded function.

Disables the vertex array called name in this shader program that was enabled by a previous call to enableAttributeArray().

enableAttributeArray(int): Enables the vertex array at location in this shader program so that the value set by setAttributeArray() on location will be used by the shader program.

See also

disableAttributeArray(), setAttributeArray(), setAttributeValue(), setUniformValue().

enableAttributeArray(str)

This is an overloaded function.

Enables the vertex array called name in this shader program so that the value set by setAttributeArray() on name will be used by the shader program.

@staticmethod hasOpenGLShaderPrograms(context: QOpenGLContext = None) → bool

Returns true if shader programs written in the OpenGL Shading Language (GLSL) are supported on this system; false otherwise.

The context is used to resolve the GLSL extensions. If context is null, then currentContext() is used.

isLinked() → bool: Returns true if this shader program has been linked; false otherwise.

See also

link().

link() → bool

Links together the shaders that were added to this program with addShader(). Returns true if the link was successful or false otherwise. If the link failed, the error messages can be retrieved with log().

Subclasses can override this function to initialize attributes and uniform variables for use in specific shader programs.

If the shader program was already linked, calling this function again will force it to be re-linked.

When shaders were added to this program via addCacheableShaderFromSourceCode() or addCacheableShaderFromSourceFile(), program binaries are supported, and a cached binary is available on disk, actual compilation and linking are skipped. Instead, will initialize the program with the binary blob via glProgramBinary(). If there is no cached version of the program or it was generated with a different driver version, the shaders will be compiled from source and the program will get linked normally. This allows seamless upgrading of the graphics drivers, without having to worry about potentially incompatible binary formats.

See also

addShader(), log().

log() → str: Returns the errors and warnings that occurred during the last link() or addShader() with explicitly specified source code.

See also

link().

maxGeometryOutputVertices() → int: Returns the hardware limit for how many vertices a geometry shader can output.

patchVertexCount() → int

Returns the number of vertices per-patch to be used when rendering.

Note: This returns the global OpenGL state value. It is not specific to this QOpenGLShaderProgram instance.

See also

setPatchVertexCount().

programId() → int: Returns the OpenGL identifier associated with this shader program.

See also

shaderId().

release(): Releases the active shader program from the current QOpenGLContext. This is equivalent to calling glUseProgram(0).

See also

bind().

removeAllShaders(): Removes all of the shaders that were added to this program previously. The QOpenGLShader objects for the shaders will not be deleted if they were constructed externally. QOpenGLShader objects that are constructed internally by QOpenGLShaderProgram will be deleted.

See also

addShader(), removeShader().

removeShader(QOpenGLShader)

Removes shader from this shader program. The object is not deleted.

The shader program must be valid in the current QOpenGLContext.

setAttributeArray(int, PYQT_SHADER_ATTRIBUTE_ARRAY): TODO

setAttributeArray(str, PYQT_SHADER_ATTRIBUTE_ARRAY): TODO

setAttributeBuffer(int, int, int, int, stride: int = 0): TODO

setAttributeBuffer(str, int, int, int, stride: int = 0): TODO

setAttributeValue(int, float): Sets the attribute at location in the current context to value.

See also

setUniformValue().

setAttributeValue(int, QVector2D): Sets the attribute at location in the current context to value.

See also

setUniformValue().

setAttributeValue(int, QVector3D): Sets the attribute at location in the current context to value.

See also

setUniformValue().

setAttributeValue(int, QVector4D): Sets the attribute at location in the current context to value.

See also

setUniformValue().

setAttributeValue(int, Union[QColor, GlobalColor, QGradient]): Sets the attribute at location in the current context to value.

See also

setUniformValue().

setAttributeValue(str, float)

This is an overloaded function.

Sets the attribute called name in the current context to value.

See also

setUniformValue().

setAttributeValue(str, QVector2D)

This is an overloaded function.

Sets the attribute called name in the current context to value.

See also

setUniformValue().

setAttributeValue(str, QVector3D)

This is an overloaded function.

Sets the attribute called name in the current context to value.

See also

setUniformValue().

setAttributeValue(str, QVector4D)

This is an overloaded function.

Sets the attribute called name in the current context to value.

See also

setUniformValue().

setAttributeValue(str, Union[QColor, GlobalColor, QGradient])

This is an overloaded function.

Sets the attribute called name in the current context to value.

See also

setUniformValue().

setAttributeValue(int, float, float): Sets the attribute at location in the current context to the 2D vector (x, y).

See also

setUniformValue().

setAttributeValue(str, float, float)

This is an overloaded function.

Sets the attribute called name in the current context to the 2D vector (x, y).

See also

setUniformValue().

setAttributeValue(int, float, float, float): Sets the attribute at location in the current context to the 3D vector (x, y, z).

See also

setUniformValue().

setAttributeValue(str, float, float, float)

This is an overloaded function.

Sets the attribute called name in the current context to the 3D vector (x, y, z).

See also

setUniformValue().

setAttributeValue(int, float, float, float, float): Sets the attribute at location in the current context to the 4D vector (x, y, z, w).

See also

setUniformValue().

setAttributeValue(str, float, float, float, float)

This is an overloaded function.

Sets the attribute called name in the current context to the 4D vector (x, y, z, w).

See also

setUniformValue().

setDefaultInnerTessellationLevels(Iterable[float])

Sets the default outer tessellation levels to be used by the tessellation primitive generator in the event that the tessellation control shader does not output them to levels. For more details on OpenGL and Tessellation shaders see OpenGL Tessellation Shaders.

The levels argument should be a QVector consisting of 2 floats. Not all of the values make sense for all tessellation modes. If you specify a vector with fewer than 2 elements, the remaining elements will be given a default value of 1.

Note: This modifies global OpenGL state and is not specific to this QOpenGLShaderProgram instance. You should call this in your render function when needed, as QOpenGLShaderProgram will not apply this for you. This is purely a convenience function.

Note: This function is only available with OpenGL >= 4.0 and is not supported with OpenGL ES 3.2.

setDefaultOuterTessellationLevels(Iterable[float])

Sets the default outer tessellation levels to be used by the tessellation primitive generator in the event that the tessellation control shader does not output them to levels. For more details on OpenGL and Tessellation shaders see OpenGL Tessellation Shaders.

The levels argument should be a QVector consisting of 4 floats. Not all of the values make sense for all tessellation modes. If you specify a vector with fewer than 4 elements, the remaining elements will be given a default value of 1.

Note: This modifies global OpenGL state and is not specific to this QOpenGLShaderProgram instance. You should call this in your render function when needed, as QOpenGLShaderProgram will not apply this for you. This is purely a convenience function.

Note: This function is only available with OpenGL >= 4.0 and is not supported with OpenGL ES 3.2.

setPatchVertexCount(int)

Use this function to specify to OpenGL the number of vertices in a patch to count. A patch is a custom OpenGL primitive whose interpretation is entirely defined by the tessellation shader stages. Therefore, calling this function only makes sense when using a QOpenGLShaderProgram containing tessellation stage shaders. When using OpenGL tessellation, the only primitive that can be rendered with glDraw\*() functions is GL_PATCHES.

This is equivalent to calling glPatchParameteri(GL_PATCH_VERTICES, count).

Note: This modifies global OpenGL state and is not specific to this QOpenGLShaderProgram instance. You should call this in your render function when needed, as QOpenGLShaderProgram will not apply this for you. This is purely a convenience function.

See also

patchVertexCount().

setUniformValue(int, int): Sets the uniform variable at location in the current context to value.

See also

setAttributeValue().

setUniformValue(int, float): Sets the uniform variable at location in the current context to value.

See also

setAttributeValue().

setUniformValue(int, QVector2D): Sets the uniform variable at location in the current context to value.

See also

setAttributeValue().

setUniformValue(int, QVector3D): Sets the uniform variable at location in the current context to value.

See also

setAttributeValue().

setUniformValue(int, QVector4D): Sets the uniform variable at location in the current context to value.

See also

setAttributeValue().

setUniformValue(int, Union[QColor, GlobalColor, QGradient]): Sets the uniform variable at location in the current context to the red, green, blue, and alpha components of color.

See also

setAttributeValue().

setUniformValue(int, QPoint): Sets the uniform variable at location in the current context to the x and y coordinates of point.

See also

setAttributeValue().

setUniformValue(int, Union[QPointF, QPoint]): Sets the uniform variable at location in the current context to the x and y coordinates of point.

See also

setAttributeValue().

setUniformValue(int, QSize): Sets the uniform variable at location in the current context to the width and height of the given size.

See also

setAttributeValue().

setUniformValue(int, QSizeF): Sets the uniform variable at location in the current context to the width and height of the given size.

See also

setAttributeValue().

setUniformValue(int, QMatrix2x2): Sets the uniform variable at location in the current context to a 2x2 matrix value.

See also

setAttributeValue().

setUniformValue(int, QMatrix2x3)

Sets the uniform variable at location in the current context to a 2x3 matrix value.

Note: This function is not aware of non square matrix support, that is, GLSL types like mat2x3, that is present in modern OpenGL versions. Instead, it treats the uniform as an array of vec3.

See also