Hello GL2 Example#

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

Hello GL2 Screenshot
# Copyright (C) 2013 Riverbank Computing Limited.
# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

"""PySide6 port of the opengl/hellogl2 example from Qt v5.x"""

from argparse import ArgumentParser, RawTextHelpFormatter
import ctypes
import math
import sys
from PySide6.QtCore import (QCoreApplication, Signal, Slot,
                            Qt, QSize, QPointF)
from PySide6.QtGui import (QVector3D, QOpenGLFunctions,
    QMatrix4x4, QOpenGLContext, QSurfaceFormat, QVector3DList)
from PySide6.QtOpenGL import (QOpenGLVertexArrayObject, QOpenGLBuffer,
    QOpenGLShaderProgram, QOpenGLShader)
from PySide6.QtWidgets import (QApplication, QWidget, QMessageBox, QHBoxLayout,
    QSlider)
from PySide6.QtOpenGLWidgets import QOpenGLWidget

from shiboken6 import VoidPtr

try:
    from OpenGL import GL
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)


class Window(QWidget):
    def __init__(self, transparent, parent=None):
        QWidget.__init__(self, parent)

        if transparent:
            self.setAttribute(Qt.WA_TranslucentBackground)
            self.setAttribute(Qt.WA_NoSystemBackground, False)

        self._gl_widget = GLWidget(transparent)

        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)

        main_layout = QHBoxLayout()
        main_layout.addWidget(self._gl_widget)
        main_layout.addWidget(self._x_slider)
        main_layout.addWidget(self._y_slider)
        main_layout.addWidget(self._z_slider)
        self.setLayout(main_layout)

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


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)


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

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

        self._transparent = transparent
        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 transparent:
            fmt = self.format()
            fmt.setAlphaBufferSize(8)
            self.setFormat(fmt)

    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):
        self.makeCurrent()
        self._logo_vbo.destroy()
        del self.program
        self.program = None
        self.doneCurrent()

    def vertex_shader_source_core(self):
        return """#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;
                }"""

    def fragment_shader_source_core(self):
        return """#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);
                }"""

    def vertex_shader_source(self):
        return """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;
                }"""

    def fragment_shader_source(self):
        return """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);
                }"""

    def initializeGL(self):
        self.context().aboutToBeDestroyed.connect(self.cleanup)
        self.initializeOpenGLFunctions()
        self.glClearColor(0, 0, 0, 0 if self._transparent else 1)

        self.program = QOpenGLShaderProgram()

        if self._core:
            self._vertex_shader = self.vertex_shader_source_core()
            self._fragment_shader = self.fragment_shader_source_core()
        else:
            self._vertex_shader = self.vertex_shader_source()
            self._fragment_shader = self.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()
        vao_binder = 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()
        vao_binder = None

    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)

        vao_binder = 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()
        vao_binder = None

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

    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


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)

    main_window = Window(options.transparent)
    main_window.resize(main_window.sizeHint())
    main_window.show()

    res = app.exec()
    sys.exit(res)