Hello GL2 Example#

The Hello GL2 example demonstrates the basic use of the OpenGL-related classes provided with Qt.

In this example the widget’s corresponding top-level window can change several times during the widget’s lifetime. Whenever this happens, the QOpenGLWidget’s associated context is destroyed and a new one is created, requiring us to clean up the GL resources.

The equivalent C++ example does this cleanup on emission of the QOpenGLContext.aboutToBeDestroyed() signal. However, in Qt for Python, we cannot rely on this signal when it is emitted from the destructor.

Therefore, we do the cleanup in GLWidget.hideEvent().

This will be followed by an invocation of initializeGL() where we can recreate all resources.

Hello GL2 Screenshot

Download this example

# Copyright (C) 2023 The Qt Company Ltd.
# Copyright (C) 2013 Riverbank Computing Limited.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

"""PySide6 port of the opengl/hellogl2 example from Qt v6.x"""

from argparse import ArgumentParser, RawTextHelpFormatter
import sys
from PySide6.QtCore import Qt
from PySide6.QtGui import QSurfaceFormat
from PySide6.QtWidgets import (QApplication, QMessageBox)


try:
    from mainwindow import MainWindow
    from glwidget import GLWidget
except ImportError:
    app = QApplication(sys.argv)
    message_box = QMessageBox(QMessageBox.Critical, "OpenGL hellogl",
                              "PyOpenGL must be installed to run this example.",
                              QMessageBox.Close)
    message_box.setDetailedText("Run:\npip install PyOpenGL PyOpenGL_accelerate")
    message_box.exec()
    sys.exit(1)


if __name__ == '__main__':
    app = QApplication(sys.argv)
    parser = ArgumentParser(description="hellogl2",
                            formatter_class=RawTextHelpFormatter)
    parser.add_argument('--multisample', '-m', action='store_true',
                        help='Use Multisampling')
    parser.add_argument('--coreprofile', '-c', action='store_true',
                        help='Use Core Profile')
    parser.add_argument('--transparent', '-t', action='store_true',
                        help='Transparent Windows')
    options = parser.parse_args()

    fmt = QSurfaceFormat()
    fmt.setDepthBufferSize(24)
    if options.multisample:
        fmt.setSamples(4)
    if options.coreprofile:
        fmt.setVersion(3, 2)
        fmt.setProfile(QSurfaceFormat.CoreProfile)
    QSurfaceFormat.setDefaultFormat(fmt)

    GLWidget.set_transparent(options.transparent)

    main_window = MainWindow()
    if options.transparent:
        main_window.setAttribute(Qt.WA_TranslucentBackground)
        main_window.setAttribute(Qt.WA_NoSystemBackground, False)

    main_window.show()

    res = app.exec()
    sys.exit(res)
# Copyright (C) 2023 The Qt Company Ltd.
# Copyright (C) 2013 Riverbank Computing Limited.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

import ctypes
from PySide6.QtCore import Signal, Slot, Qt, QSize, QPointF
from PySide6.QtGui import (QVector3D, QOpenGLFunctions,
                           QMatrix4x4, QOpenGLContext, QSurfaceFormat)
from PySide6.QtOpenGL import (QOpenGLVertexArrayObject, QOpenGLBuffer,
                              QOpenGLShaderProgram, QOpenGLShader)
from PySide6.QtOpenGLWidgets import QOpenGLWidget

from OpenGL import GL

from shiboken6 import VoidPtr
from logo import Logo

FRAGMENT_SHADER_SOURCE_CORE = """#version 150
in highp vec3 vert;
in highp vec3 vertNormal;
out highp vec4 fragColor;
uniform highp vec3 lightPos;
void main() {
   highp vec3 L = normalize(lightPos - vert);
   highp float NL = max(dot(normalize(vertNormal), L), 0.0);
   highp vec3 color = vec3(0.39, 1.0, 0.0);
   highp vec3 col = clamp(color * 0.2 + color * 0.8 * NL, 0.0, 1.0);
   fragColor = vec4(col, 1.0);
}"""


FRAGMENT_SHADER_SOURCE = """varying highp vec3 vert;
varying highp vec3 vertNormal;
uniform highp vec3 lightPos;
void main() {
   highp vec3 L = normalize(lightPos - vert);
   highp float NL = max(dot(normalize(vertNormal), L), 0.0);
   highp vec3 color = vec3(0.39, 1.0, 0.0);
   highp vec3 col = clamp(color * 0.2 + color * 0.8 * NL, 0.0, 1.0);
   gl_FragColor = vec4(col, 1.0);
}"""


VERTEX_SHADER_SOURCE_CORE = """#version 150
in vec4 vertex;
in vec3 normal;
out vec3 vert;
out vec3 vertNormal;
uniform mat4 projMatrix;
uniform mat4 mvMatrix;
uniform mat3 normalMatrix;
void main() {
   vert = vertex.xyz;
   vertNormal = normalMatrix * normal;
   gl_Position = projMatrix * mvMatrix * vertex;
}"""


VERTEX_SHADER_SOURCE = """attribute vec4 vertex;
attribute vec3 normal;
varying vec3 vert;
varying vec3 vertNormal;
uniform mat4 projMatrix;
uniform mat4 mvMatrix;
uniform mat3 normalMatrix;
void main() {
   vert = vertex.xyz;
   vertNormal = normalMatrix * normal;
   gl_Position = projMatrix * mvMatrix * vertex;
}"""


class GLWidget(QOpenGLWidget, QOpenGLFunctions):
    x_rotation_changed = Signal(int)
    y_rotation_changed = Signal(int)
    z_rotation_changed = Signal(int)

    _transparent = False

    def __init__(self, parent=None):
        QOpenGLWidget.__init__(self, parent)
        QOpenGLFunctions.__init__(self)

        self._core = QSurfaceFormat.defaultFormat().profile() == QSurfaceFormat.CoreProfile

        self._x_rot = 0
        self._y_rot = 0
        self._z_rot = 0
        self._last_pos = QPointF()
        self.logo = Logo()
        self.vao = QOpenGLVertexArrayObject()
        self._logo_vbo = QOpenGLBuffer()
        self.program = QOpenGLShaderProgram()
        self._proj_matrix_loc = 0
        self._mv_matrix_loc = 0
        self._normal_matrix_loc = 0
        self._light_pos_loc = 0
        self.proj = QMatrix4x4()
        self.camera = QMatrix4x4()
        self.world = QMatrix4x4()
        if self._transparent:
            fmt = self.format()
            fmt.setAlphaBufferSize(8)
            self.setFormat(fmt)

    @staticmethod
    def set_transparent(t):
        GLWidget._transparent = t

    @staticmethod
    def is_transparent():
        return GLWidget._transparent

    def x_rotation(self):
        return self._x_rot

    def y_rotation(self):
        return self._y_rot

    def z_rotation(self):
        return self._z_rot

    def minimumSizeHint(self):
        return QSize(50, 50)

    def sizeHint(self):
        return QSize(400, 400)

    def normalize_angle(self, angle):
        while angle < 0:
            angle += 360 * 16
        while angle > 360 * 16:
            angle -= 360 * 16
        return angle

    @Slot(int)
    def set_xrotation(self, angle):
        angle = self.normalize_angle(angle)
        if angle != self._x_rot:
            self._x_rot = angle
            self.x_rotation_changed.emit(angle)
            self.update()

    @Slot(int)
    def set_yrotation(self, angle):
        angle = self.normalize_angle(angle)
        if angle != self._y_rot:
            self._y_rot = angle
            self.y_rotation_changed.emit(angle)
            self.update()

    @Slot(int)
    def set_zrotation(self, angle):
        angle = self.normalize_angle(angle)
        if angle != self._z_rot:
            self._z_rot = angle
            self.z_rotation_changed.emit(angle)
            self.update()

    @Slot()
    def cleanup(self):
        if self.program:
            self.makeCurrent()
            self._logo_vbo.destroy()
            del self.program
            self.program = None
            self.doneCurrent()

    def initializeGL(self):
        self.initializeOpenGLFunctions()
        self.glClearColor(0, 0, 0, 0 if self._transparent else 1)

        self.program = QOpenGLShaderProgram()

        if self._core:
            self._vertex_shader = VERTEX_SHADER_SOURCE_CORE
            self._fragment_shader = FRAGMENT_SHADER_SOURCE_CORE
        else:
            self._vertex_shader = VERTEX_SHADER_SOURCE
            self._fragment_shader = FRAGMENT_SHADER_SOURCE

        self.program.addShaderFromSourceCode(QOpenGLShader.Vertex,
                                             self._vertex_shader)
        self.program.addShaderFromSourceCode(QOpenGLShader.Fragment,
                                             self._fragment_shader)
        self.program.bindAttributeLocation("vertex", 0)
        self.program.bindAttributeLocation("normal", 1)
        self.program.link()

        self.program.bind()
        self._proj_matrix_loc = self.program.uniformLocation("projMatrix")
        self._mv_matrix_loc = self.program.uniformLocation("mvMatrix")
        self._normal_matrix_loc = self.program.uniformLocation("normalMatrix")
        self._light_pos_loc = self.program.uniformLocation("lightPos")

        self.vao.create()
        with QOpenGLVertexArrayObject.Binder(self.vao):
            self._logo_vbo.create()
            self._logo_vbo.bind()
            float_size = ctypes.sizeof(ctypes.c_float)
            self._logo_vbo.allocate(self.logo.const_data(),
                                    self.logo.count() * float_size)

            self.setup_vertex_attribs()

            self.camera.setToIdentity()
            self.camera.translate(0, 0, -1)

            self.program.setUniformValue(self._light_pos_loc,
                                         QVector3D(0, 0, 70))
            self.program.release()

    def setup_vertex_attribs(self):
        self._logo_vbo.bind()
        f = QOpenGLContext.currentContext().functions()
        f.glEnableVertexAttribArray(0)
        f.glEnableVertexAttribArray(1)
        float_size = ctypes.sizeof(ctypes.c_float)

        null = VoidPtr(0)
        pointer = VoidPtr(3 * float_size)
        f.glVertexAttribPointer(0, 3, int(GL.GL_FLOAT), int(GL.GL_FALSE),
                                6 * float_size, null)
        f.glVertexAttribPointer(1, 3, int(GL.GL_FLOAT), int(GL.GL_FALSE),
                                6 * float_size, pointer)
        self._logo_vbo.release()

    def paintGL(self):
        self.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT)
        self.glEnable(GL.GL_DEPTH_TEST)
        self.glEnable(GL.GL_CULL_FACE)

        self.world.setToIdentity()
        self.world.rotate(180 - (self._x_rot / 16), 1, 0, 0)
        self.world.rotate(self._y_rot / 16, 0, 1, 0)
        self.world.rotate(self._z_rot / 16, 0, 0, 1)

        with QOpenGLVertexArrayObject.Binder(self.vao):
            self.program.bind()
            self.program.setUniformValue(self._proj_matrix_loc, self.proj)
            self.program.setUniformValue(self._mv_matrix_loc,
                                         self.camera * self.world)
            normal_matrix = self.world.normalMatrix()
            self.program.setUniformValue(self._normal_matrix_loc, normal_matrix)

            self.glDrawArrays(GL.GL_TRIANGLES, 0, self.logo.vertex_count())
            self.program.release()

    def resizeGL(self, width, height):
        self.proj.setToIdentity()
        self.proj.perspective(45, width / height, 0.01, 100)

    def hideEvent(self, event):
        self.cleanup()
        super().hideEvent(event)

    def mousePressEvent(self, event):
        self._last_pos = event.position()

    def mouseMoveEvent(self, event):
        pos = event.position()
        dx = pos.x() - self._last_pos.x()
        dy = pos.y() - self._last_pos.y()

        if event.buttons() & Qt.LeftButton:
            self.set_xrotation(self._x_rot + 8 * dy)
            self.set_yrotation(self._y_rot + 8 * dx)
        elif event.buttons() & Qt.RightButton:
            self.set_xrotation(self._x_rot + 8 * dy)
            self.set_zrotation(self._z_rot + 8 * dx)

        self._last_pos = pos
# Copyright (C) 2023 The Qt Company Ltd.
# Copyright (C) 2013 Riverbank Computing Limited.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

import math

from PySide6.QtGui import (QVector3D, QVector3DList)


class Logo():
    def __init__(self):
        self.m_data = QVector3DList()
        self.m_data.reserve(5000)

        x1 = +0.06
        y1 = -0.14
        x2 = +0.14
        y2 = -0.06
        x3 = +0.08
        y3 = +0.00
        x4 = +0.30
        y4 = +0.22

        self.quad(x1, y1, x2, y2, y2, x2, y1, x1)
        self.quad(x3, y3, x4, y4, y4, x4, y3, x3)

        self.extrude(x1, y1, x2, y2)
        self.extrude(x2, y2, y2, x2)
        self.extrude(y2, x2, y1, x1)
        self.extrude(y1, x1, x1, y1)
        self.extrude(x3, y3, x4, y4)
        self.extrude(x4, y4, y4, x4)
        self.extrude(y4, x4, y3, x3)

        NUM_SECTORS = 100

        for i in range(NUM_SECTORS):
            angle = (i * 2 * math.pi) / NUM_SECTORS
            x5 = 0.30 * math.sin(angle)
            y5 = 0.30 * math.cos(angle)
            x6 = 0.20 * math.sin(angle)
            y6 = 0.20 * math.cos(angle)

            angle = ((i + 1) * 2 * math.pi) / NUM_SECTORS
            x7 = 0.20 * math.sin(angle)
            y7 = 0.20 * math.cos(angle)
            x8 = 0.30 * math.sin(angle)
            y8 = 0.30 * math.cos(angle)

            self.quad(x5, y5, x6, y6, x7, y7, x8, y8)

            self.extrude(x6, y6, x7, y7)
            self.extrude(x8, y8, x5, y5)

    def const_data(self):
        return self.m_data.constData()

    def count(self):
        return len(self.m_data) * 3

    def vertex_count(self):
        return self.count() / 6

    def quad(self, x1, y1, x2, y2, x3, y3, x4, y4):
        n = QVector3D.normal(QVector3D(x4 - x1, y4 - y1, 0),
                             QVector3D(x2 - x1, y2 - y1, 0))

        self.add(QVector3D(x1, y1, -0.05), n)
        self.add(QVector3D(x4, y4, -0.05), n)
        self.add(QVector3D(x2, y2, -0.05), n)

        self.add(QVector3D(x3, y3, -0.05), n)
        self.add(QVector3D(x2, y2, -0.05), n)
        self.add(QVector3D(x4, y4, -0.05), n)

        n = QVector3D.normal(QVector3D(x1 - x4, y1 - y4, 0),
                             QVector3D(x2 - x4, y2 - y4, 0))

        self.add(QVector3D(x4, y4, 0.05), n)
        self.add(QVector3D(x1, y1, 0.05), n)
        self.add(QVector3D(x2, y2, 0.05), n)

        self.add(QVector3D(x2, y2, 0.05), n)
        self.add(QVector3D(x3, y3, 0.05), n)
        self.add(QVector3D(x4, y4, 0.05), n)

    def extrude(self, x1, y1, x2, y2):
        n = QVector3D.normal(QVector3D(0, 0, -0.1),
                             QVector3D(x2 - x1, y2 - y1, 0))

        self.add(QVector3D(x1, y1, 0.05), n)
        self.add(QVector3D(x1, y1, -0.05), n)
        self.add(QVector3D(x2, y2, 0.05), n)

        self.add(QVector3D(x2, y2, -0.05), n)
        self.add(QVector3D(x2, y2, 0.05), n)
        self.add(QVector3D(x1, y1, -0.05), n)

    def add(self, v, n):
        self.m_data.append(v)
        self.m_data.append(n)
# Copyright (C) 2023 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

from PySide6.QtCore import Slot, Qt
from PySide6.QtGui import QKeySequence
from PySide6.QtWidgets import QMainWindow, QMessageBox

from window import Window


class MainWindow(QMainWindow):

    def __init__(self):
        super().__init__()
        menuWindow = self.menuBar().addMenu("Window")
        menuWindow.addAction("Add new", QKeySequence(Qt.CTRL | Qt.Key_N),
                             self.onAddNew)
        menuWindow.addAction("Quit", QKeySequence(Qt.CTRL | Qt.Key_Q),
                             qApp.closeAllWindows)  # noqa: F821

        self.onAddNew()

    @Slot()
    def onAddNew(self):
        if not self.centralWidget():
            self.setCentralWidget(Window(self))
        else:
            QMessageBox.information(self, "Cannot Add Window()",
                                    "Already occupied. Undock first.")
# Copyright (C) 2023 The Qt Company Ltd.
# Copyright (C) 2013 Riverbank Computing Limited.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

from PySide6.QtCore import Slot, Qt
from PySide6.QtWidgets import (QHBoxLayout, QMainWindow,
                               QMessageBox, QPushButton, QSlider,
                               QVBoxLayout, QWidget)

from glwidget import GLWidget


def _main_window():
    for t in qApp.topLevelWidgets():  # noqa: F821
        if isinstance(t, QMainWindow):
            return t
    return None


class Window(QWidget):
    instances = []  # Keep references when undocked

    def __init__(self, parent=None):
        super().__init__(parent)
        self.instances.append(self)

        self._gl_widget = GLWidget()

        self._x_slider = self.create_slider()
        self._x_slider.valueChanged.connect(self._gl_widget.set_xrotation)
        self._gl_widget.x_rotation_changed.connect(self._x_slider.setValue)

        self._y_slider = self.create_slider()
        self._y_slider.valueChanged.connect(self._gl_widget.set_yrotation)
        self._gl_widget.y_rotation_changed.connect(self._y_slider.setValue)

        self._z_slider = self.create_slider()
        self._z_slider.valueChanged.connect(self._gl_widget.set_zrotation)
        self._gl_widget.z_rotation_changed.connect(self._z_slider.setValue)

        mainLayout = QVBoxLayout(self)
        w = QWidget()
        container = QHBoxLayout(w)
        container.addWidget(self._gl_widget)
        container.addWidget(self._x_slider)
        container.addWidget(self._y_slider)
        container.addWidget(self._z_slider)

        mainLayout.addWidget(w)
        self._dock_btn = QPushButton("Undock")
        self._dock_btn.clicked.connect(self.dock_undock)
        mainLayout.addWidget(self._dock_btn)

        self._x_slider.setValue(15 * 16)
        self._y_slider.setValue(345 * 16)
        self._z_slider.setValue(0 * 16)

        self.setWindowTitle(self.tr("Hello GL"))

    def create_slider(self):
        slider = QSlider(Qt.Vertical)

        slider.setRange(0, 360 * 16)
        slider.setSingleStep(16)
        slider.setPageStep(15 * 16)
        slider.setTickInterval(15 * 16)
        slider.setTickPosition(QSlider.TicksRight)
        return slider

    def closeEvent(self, event):
        self.instances.remove(self)
        event.accept()

    def keyPressEvent(self, event):
        if self.isWindow() and event.key() == Qt.Key_Escape:
            self.close()
        else:
            super().keyPressEvent(event)

    @Slot()
    def dock_undock(self):
        if self.parent():
            self.undock()
        else:
            self.dock()

    def dock(self):
        mainWindow = _main_window()
        if not mainWindow or not mainWindow.isVisible():
            QMessageBox.information(self, "Cannot Dock",
                                    "Main window already closed")
            return
        if mainWindow.centralWidget():
            QMessageBox.information(self, "Cannot Dock",
                                    "Main window already occupied")
            return

        self.setAttribute(Qt.WA_DeleteOnClose, False)
        self._dock_btn.setText("Undock")
        mainWindow.setCentralWidget(self)

    def undock(self):
        self.setParent(None)
        self.setAttribute(Qt.WA_DeleteOnClose)
        geometry = self.screen().availableGeometry()
        x = geometry.x() + (geometry.width() - self.width()) / 2
        y = geometry.y() + (geometry.height() - self.height()) / 2
        self.move(x, y)
        self._dock_btn.setText("Dock")
        self.show()