glwidget.cpp Example File

textures/glwidget.cpp 
 /****************************************************************************
 **
 ** Copyright (C) 2016 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
 **
 ** $QT_BEGIN_LICENSE:BSD$
 ** Commercial License Usage
 ** Licensees holding valid commercial Qt licenses may use this file in
 ** accordance with the commercial license agreement provided with the
 ** Software or, alternatively, in accordance with the terms contained in
 ** a written agreement between you and The Qt Company. For licensing terms
 ** and conditions see https://www.qt.io/terms-conditions. For further
 ** information use the contact form at https://www.qt.io/contact-us.
 **
 ** BSD License Usage
 ** Alternatively, you may use this file under the terms of the BSD license
 ** as follows:
 **
 ** "Redistribution and use in source and binary forms, with or without
 ** modification, are permitted provided that the following conditions are
 ** met:
 **   * Redistributions of source code must retain the above copyright
 **     notice, this list of conditions and the following disclaimer.
 **   * Redistributions in binary form must reproduce the above copyright
 **     notice, this list of conditions and the following disclaimer in
 **     the documentation and/or other materials provided with the
 **     distribution.
 **   * Neither the name of The Qt Company Ltd nor the names of its
 **     contributors may be used to endorse or promote products derived
 **     from this software without specific prior written permission.
 **
 **
 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
 **
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/

 #include "glwidget.h"
 #include <QOpenGLShaderProgram>
 #include <QOpenGLTexture>
 #include <QMouseEvent>

 GLWidget::GLWidget(QWidget *parent)
     : QOpenGLWidget(parent),
       clearColor(Qt::black),
       xRot(0),
       yRot(0),
       zRot(0),
       program(0)
 {
     memset(textures, 0, sizeof(textures));
 }

 GLWidget::~GLWidget()
 {
     makeCurrent();
     vbo.destroy();
     for (int i = 0; i < 6; ++i)
         delete textures[i];
     delete program;
     doneCurrent();
 }

 QSize GLWidget::minimumSizeHint() const
 {
     return QSize(50, 50);
 }

 QSize GLWidget::sizeHint() const
 {
     return QSize(200, 200);
 }

 void GLWidget::rotateBy(int xAngle, int yAngle, int zAngle)
 {
     xRot += xAngle;
     yRot += yAngle;
     zRot += zAngle;
     update();
 }

 void GLWidget::setClearColor(const QColor &color)
 {
     clearColor = color;
     update();
 }

 void GLWidget::initializeGL()
 {
     initializeOpenGLFunctions();

     makeObject();

     glEnable(GL_DEPTH_TEST);
     glEnable(GL_CULL_FACE);

 #define PROGRAM_VERTEX_ATTRIBUTE 0
 #define PROGRAM_TEXCOORD_ATTRIBUTE 1

     QOpenGLShader *vshader = new QOpenGLShader(QOpenGLShader::Vertex, this);
     const char *vsrc =
         "attribute highp vec4 vertex;\n"
         "attribute mediump vec4 texCoord;\n"
         "varying mediump vec4 texc;\n"
         "uniform mediump mat4 matrix;\n"
         "void main(void)\n"
         "{\n"
         "    gl_Position = matrix * vertex;\n"
         "    texc = texCoord;\n"
         "}\n";
     vshader->compileSourceCode(vsrc);

     QOpenGLShader *fshader = new QOpenGLShader(QOpenGLShader::Fragment, this);
     const char *fsrc =
         "uniform sampler2D texture;\n"
         "varying mediump vec4 texc;\n"
         "void main(void)\n"
         "{\n"
         "    gl_FragColor = texture2D(texture, texc.st);\n"
         "}\n";
     fshader->compileSourceCode(fsrc);

     program = new QOpenGLShaderProgram;
     program->addShader(vshader);
     program->addShader(fshader);
     program->bindAttributeLocation("vertex", PROGRAM_VERTEX_ATTRIBUTE);
     program->bindAttributeLocation("texCoord", PROGRAM_TEXCOORD_ATTRIBUTE);
     program->link();

     program->bind();
     program->setUniformValue("texture", 0);
 }

 void GLWidget::paintGL()
 {
     glClearColor(clearColor.redF(), clearColor.greenF(), clearColor.blueF(), clearColor.alphaF());
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

     QMatrix4x4 m;
     m.ortho(-0.5f, +0.5f, +0.5f, -0.5f, 4.0f, 15.0f);
     m.translate(0.0f, 0.0f, -10.0f);
     m.rotate(xRot / 16.0f, 1.0f, 0.0f, 0.0f);
     m.rotate(yRot / 16.0f, 0.0f, 1.0f, 0.0f);
     m.rotate(zRot / 16.0f, 0.0f, 0.0f, 1.0f);

     program->setUniformValue("matrix", m);
     program->enableAttributeArray(PROGRAM_VERTEX_ATTRIBUTE);
     program->enableAttributeArray(PROGRAM_TEXCOORD_ATTRIBUTE);
     program->setAttributeBuffer(PROGRAM_VERTEX_ATTRIBUTE, GL_FLOAT, 0, 3, 5 * sizeof(GLfloat));
     program->setAttributeBuffer(PROGRAM_TEXCOORD_ATTRIBUTE, GL_FLOAT, 3 * sizeof(GLfloat), 2, 5 * sizeof(GLfloat));

     for (int i = 0; i < 6; ++i) {
         textures[i]->bind();
         glDrawArrays(GL_TRIANGLE_FAN, i * 4, 4);
     }
 }
 void GLWidget::resizeGL(int width, int height)
 {
     int side = qMin(width, height);
     glViewport((width - side) / 2, (height - side) / 2, side, side);
 }

 void GLWidget::mousePressEvent(QMouseEvent *event)
 {
     lastPos = event->pos();
 }

 void GLWidget::mouseMoveEvent(QMouseEvent *event)
 {
     int dx = event->x() - lastPos.x();
     int dy = event->y() - lastPos.y();

     if (event->buttons() & Qt::LeftButton) {
         rotateBy(8 * dy, 8 * dx, 0);
     } else if (event->buttons() & Qt::RightButton) {
         rotateBy(8 * dy, 0, 8 * dx);
     }
     lastPos = event->pos();
 }

 void GLWidget::mouseReleaseEvent(QMouseEvent * /* event */)
 {
     emit clicked();
 }

 void GLWidget::makeObject()
 {
     static const int coords[6][4][3] = {
         { { +1, -1, -1 }, { -1, -1, -1 }, { -1, +1, -1 }, { +1, +1, -1 } },
         { { +1, +1, -1 }, { -1, +1, -1 }, { -1, +1, +1 }, { +1, +1, +1 } },
         { { +1, -1, +1 }, { +1, -1, -1 }, { +1, +1, -1 }, { +1, +1, +1 } },
         { { -1, -1, -1 }, { -1, -1, +1 }, { -1, +1, +1 }, { -1, +1, -1 } },
         { { +1, -1, +1 }, { -1, -1, +1 }, { -1, -1, -1 }, { +1, -1, -1 } },
         { { -1, -1, +1 }, { +1, -1, +1 }, { +1, +1, +1 }, { -1, +1, +1 } }
     };

     for (int j = 0; j < 6; ++j)
         textures[j] = new QOpenGLTexture(QImage(QString(":/images/side%1.png").arg(j + 1)).mirrored());

     QVector<GLfloat> vertData;
     for (int i = 0; i < 6; ++i) {
         for (int j = 0; j < 4; ++j) {
             // vertex position
             vertData.append(0.2 * coords[i][j][0]);
             vertData.append(0.2 * coords[i][j][1]);
             vertData.append(0.2 * coords[i][j][2]);
             // texture coordinate
             vertData.append(j == 0 || j == 3);
             vertData.append(j == 0 || j == 1);
         }
     }

     vbo.create();
     vbo.bind();
     vbo.allocate(vertData.constData(), vertData.count() * sizeof(GLfloat));
 }

© 2020 The Qt Company Ltd. Documentation contributions included herein are the copyrights of their respective owners.
The documentation provided herein is licensed under the terms of the GNU Free Documentation License version 1.3 as published by the Free Software Foundation.
Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property of their respective owners.