Qt 5.6 | Qt OpenGL | Hello GL2 Example | glwidget.cpp Example File

Qt 5.6.2 Reference Documentation

# glwidget.cpp Example File

hellogl2/glwidget.cpp

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      #include "glwidget.h"
      #include <QMouseEvent>
      #include <QOpenGLShaderProgram>
      #include <QCoreApplication>
      #include <math.h>

      GLWidget::GLWidget(QWidget *parent)
          : QOpenGLWidget(parent),
            m_xRot(0),
            m_yRot(0),
            m_zRot(0),
            m_program(0)
      {
          m_core = QCoreApplication::arguments().contains(QStringLiteral("--coreprofile"));
          // --transparent causes the clear color to be transparent. Therefore, on systems that
          // support it, the widget will become transparent apart from the logo.
          m_transparent = QCoreApplication::arguments().contains(QStringLiteral("--transparent"));
          if (m_transparent) {
              QSurfaceFormat fmt = format();
              fmt.setAlphaBufferSize(8);
              setFormat(fmt);
          }
      }

      GLWidget::~GLWidget()
      {
          cleanup();
      }

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

      QSize GLWidget::sizeHint() const
      {
          return QSize(400, 400);
      }

      static void qNormalizeAngle(int &angle)
      {
          while (angle < 0)
              angle += 360 * 16;
          while (angle > 360 * 16)
              angle -= 360 * 16;
      }

      void GLWidget::setXRotation(int angle)
      {
          qNormalizeAngle(angle);
          if (angle != m_xRot) {
              m_xRot = angle;
              emit xRotationChanged(angle);
              update();
          }
      }

      void GLWidget::setYRotation(int angle)
      {
          qNormalizeAngle(angle);
          if (angle != m_yRot) {
              m_yRot = angle;
              emit yRotationChanged(angle);
              update();
          }
      }

      void GLWidget::setZRotation(int angle)
      {
          qNormalizeAngle(angle);
          if (angle != m_zRot) {
              m_zRot = angle;
              emit zRotationChanged(angle);
              update();
          }
      }

      void GLWidget::cleanup()
      {
          makeCurrent();
          m_logoVbo.destroy();
          delete m_program;
          m_program = 0;
          doneCurrent();
      }

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

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

      static const char *vertexShaderSource =
          "attribute vec4 vertex;\n"
          "attribute vec3 normal;\n"
          "varying vec3 vert;\n"
          "varying vec3 vertNormal;\n"
          "uniform mat4 projMatrix;\n"
          "uniform mat4 mvMatrix;\n"
          "uniform mat3 normalMatrix;\n"
          "void main() {\n"
          "   vert = vertex.xyz;\n"
          "   vertNormal = normalMatrix * normal;\n"
          "   gl_Position = projMatrix * mvMatrix * vertex;\n"
          "}\n";

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

      void GLWidget::initializeGL()
      {
          // 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.
          // Therefore we have to be prepared to clean up the resources on the
          // aboutToBeDestroyed() signal, instead of the destructor. The emission of
          // the signal will be followed by an invocation of initializeGL() where we
          // can recreate all resources.
          connect(context(), &QOpenGLContext::aboutToBeDestroyed, this, &GLWidget::cleanup);

          initializeOpenGLFunctions();
          glClearColor(0, 0, 0, m_transparent ? 0 : 1);

          m_program = new QOpenGLShaderProgram;
          m_program->addShaderFromSourceCode(QOpenGLShader::Vertex, m_core ? vertexShaderSourceCore : vertexShaderSource);
          m_program->addShaderFromSourceCode(QOpenGLShader::Fragment, m_core ? fragmentShaderSourceCore : fragmentShaderSource);
          m_program->bindAttributeLocation("vertex", 0);
          m_program->bindAttributeLocation("normal", 1);
          m_program->link();

          m_program->bind();
          m_projMatrixLoc = m_program->uniformLocation("projMatrix");
          m_mvMatrixLoc = m_program->uniformLocation("mvMatrix");
          m_normalMatrixLoc = m_program->uniformLocation("normalMatrix");
          m_lightPosLoc = m_program->uniformLocation("lightPos");

          // Create a vertex array object. In OpenGL ES 2.0 and OpenGL 2.x
          // implementations this is optional and support may not be present
          // at all. Nonetheless the below code works in all cases and makes
          // sure there is a VAO when one is needed.
          m_vao.create();
          QOpenGLVertexArrayObject::Binder vaoBinder(&m_vao);

          // Setup our vertex buffer object.
          m_logoVbo.create();
          m_logoVbo.bind();
          m_logoVbo.allocate(m_logo.constData(), m_logo.count() * sizeof(GLfloat));

          // Store the vertex attribute bindings for the program.
          setupVertexAttribs();

          // Our camera never changes in this example.
          m_camera.setToIdentity();
          m_camera.translate(0, 0, -1);

          // Light position is fixed.
          m_program->setUniformValue(m_lightPosLoc, QVector3D(0, 0, 70));

          m_program->release();
      }

      void GLWidget::setupVertexAttribs()
      {
          m_logoVbo.bind();
          QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions();
          f->glEnableVertexAttribArray(0);
          f->glEnableVertexAttribArray(1);
          f->glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), 0);
          f->glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), reinterpret_cast<void *>(3 * sizeof(GLfloat)));
          m_logoVbo.release();
      }

      void GLWidget::paintGL()
      {
          glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
          glEnable(GL_DEPTH_TEST);
          glEnable(GL_CULL_FACE);

          m_world.setToIdentity();
          m_world.rotate(180.0f - (m_xRot / 16.0f), 1, 0, 0);
          m_world.rotate(m_yRot / 16.0f, 0, 1, 0);
          m_world.rotate(m_zRot / 16.0f, 0, 0, 1);

          QOpenGLVertexArrayObject::Binder vaoBinder(&m_vao);
          m_program->bind();
          m_program->setUniformValue(m_projMatrixLoc, m_proj);
          m_program->setUniformValue(m_mvMatrixLoc, m_camera * m_world);
          QMatrix3x3 normalMatrix = m_world.normalMatrix();
          m_program->setUniformValue(m_normalMatrixLoc, normalMatrix);

          glDrawArrays(GL_TRIANGLES, 0, m_logo.vertexCount());

          m_program->release();
      }

      void GLWidget::resizeGL(int w, int h)
      {
          m_proj.setToIdentity();
          m_proj.perspective(45.0f, GLfloat(w) / h, 0.01f, 100.0f);
      }

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

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

          if (event->buttons() & Qt::LeftButton) {
              setXRotation(m_xRot + 8 * dy);
              setYRotation(m_yRot + 8 * dx);
          } else if (event->buttons() & Qt::RightButton) {
              setXRotation(m_xRot + 8 * dy);
              setZRotation(m_zRot + 8 * dx);
          }
          m_lastPos = event->pos();
      }