Qt 5.11 | Qt OpenGL | Textures Example | glwidget.cpp Example File

Qt 5.11.3 Reference Documentation

# glwidget.cpp Example File

textures/glwidget.cpp

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      #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));
      }