Qt 5.11 | Qt Quick | QQuickRenderControl Example | cuberenderer.cpp Example File

Qt 5.11.3 Reference Documentation

# cuberenderer.cpp Example File

rendercontrol/cuberenderer.cpp

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      #include "cuberenderer.h"
      #include <QOpenGLContext>
      #include <QOpenGLFunctions>
      #include <QOpenGLShaderProgram>
      #include <QOpenGLVertexArrayObject>
      #include <QOpenGLBuffer>
      #include <QOpenGLVertexArrayObject>
      #include <QOffscreenSurface>
      #include <QWindow>

      CubeRenderer::CubeRenderer(QOffscreenSurface *offscreenSurface)
          : m_offscreenSurface(offscreenSurface),
            m_context(nullptr),
            m_program(nullptr),
            m_vbo(nullptr),
            m_vao(nullptr),
            m_matrixLoc(0)
      {
      }

      CubeRenderer::~CubeRenderer()
      {
          // Use a temporary offscreen surface to do the cleanup.
          // There may not be a native window surface available anymore at this stage.
          m_context->makeCurrent(m_offscreenSurface);

          delete m_program;
          delete m_vbo;
          delete m_vao;

          m_context->doneCurrent();
          delete m_context;
      }

      void CubeRenderer::init(QWindow *w, QOpenGLContext *share)
      {
          m_context = new QOpenGLContext;
          m_context->setShareContext(share);
          m_context->setFormat(w->requestedFormat());
          m_context->create();
          if (!m_context->makeCurrent(w))
              return;

          QOpenGLFunctions *f = m_context->functions();
          f->glClearColor(0.0f, 0.1f, 0.25f, 1.0f);
          f->glViewport(0, 0, w->width() * w->devicePixelRatio(), w->height() * w->devicePixelRatio());

          static const char *vertexShaderSource =
              "attribute highp vec4 vertex;\n"
              "attribute lowp vec2 coord;\n"
              "varying lowp vec2 v_coord;\n"
              "uniform highp mat4 matrix;\n"
              "void main() {\n"
              "   v_coord = coord;\n"
              "   gl_Position = matrix * vertex;\n"
              "}\n";
          static const char *fragmentShaderSource =
              "varying lowp vec2 v_coord;\n"
              "uniform sampler2D sampler;\n"
              "void main() {\n"
              "   gl_FragColor = vec4(texture2D(sampler, v_coord).rgb, 1.0);\n"
              "}\n";
          m_program = new QOpenGLShaderProgram;
          m_program->addCacheableShaderFromSourceCode(QOpenGLShader::Vertex, vertexShaderSource);
          m_program->addCacheableShaderFromSourceCode(QOpenGLShader::Fragment, fragmentShaderSource);
          m_program->bindAttributeLocation("vertex", 0);
          m_program->bindAttributeLocation("coord", 1);
          m_program->link();
          m_matrixLoc = m_program->uniformLocation("matrix");

          m_vao = new QOpenGLVertexArrayObject;
          m_vao->create();
          QOpenGLVertexArrayObject::Binder vaoBinder(m_vao);

          m_vbo = new QOpenGLBuffer;
          m_vbo->create();
          m_vbo->bind();

          GLfloat v[] = {
              -0.5, 0.5, 0.5, 0.5,-0.5,0.5,-0.5,-0.5,0.5,
              0.5, -0.5, 0.5, -0.5,0.5,0.5,0.5,0.5,0.5,
              -0.5, -0.5, -0.5, 0.5,-0.5,-0.5,-0.5,0.5,-0.5,
              0.5, 0.5, -0.5, -0.5,0.5,-0.5,0.5,-0.5,-0.5,

              0.5, -0.5, -0.5, 0.5,-0.5,0.5,0.5,0.5,-0.5,
              0.5, 0.5, 0.5, 0.5,0.5,-0.5,0.5,-0.5,0.5,
              -0.5, 0.5, -0.5, -0.5,-0.5,0.5,-0.5,-0.5,-0.5,
              -0.5, -0.5, 0.5, -0.5,0.5,-0.5,-0.5,0.5,0.5,

              0.5, 0.5,  -0.5, -0.5, 0.5,  0.5,  -0.5,  0.5,  -0.5,
              -0.5,  0.5,  0.5,  0.5,  0.5,  -0.5, 0.5, 0.5,  0.5,
              -0.5,  -0.5, -0.5, -0.5, -0.5, 0.5,  0.5, -0.5, -0.5,
              0.5, -0.5, 0.5,  0.5,  -0.5, -0.5, -0.5,  -0.5, 0.5
          };
          GLfloat texCoords[] = {
              0.0f,0.0f, 1.0f,1.0f, 1.0f,0.0f,
              1.0f,1.0f, 0.0f,0.0f, 0.0f,1.0f,
              1.0f,1.0f, 1.0f,0.0f, 0.0f,1.0f,
              0.0f,0.0f, 0.0f,1.0f, 1.0f,0.0f,

              1.0f,1.0f, 1.0f,0.0f, 0.0f,1.0f,
              0.0f,0.0f, 0.0f,1.0f, 1.0f,0.0f,
              0.0f,0.0f, 1.0f,1.0f, 1.0f,0.0f,
              1.0f,1.0f, 0.0f,0.0f, 0.0f,1.0f,

              0.0f,1.0f, 1.0f,0.0f, 1.0f,1.0f,
              1.0f,0.0f, 0.0f,1.0f, 0.0f,0.0f,
              1.0f,0.0f, 1.0f,1.0f, 0.0f,0.0f,
              0.0f,1.0f, 0.0f,0.0f, 1.0f,1.0f
          };

          const int vertexCount = 36;
          m_vbo->allocate(sizeof(GLfloat) * vertexCount * 5);
          m_vbo->write(0, v, sizeof(GLfloat) * vertexCount * 3);
          m_vbo->write(sizeof(GLfloat) * vertexCount * 3, texCoords, sizeof(GLfloat) * vertexCount * 2);
          m_vbo->release();

          if (m_vao->isCreated())
              setupVertexAttribs();
      }

      void CubeRenderer::resize(int w, int h)
      {
          m_proj.setToIdentity();
          m_proj.perspective(45, w / float(h), 0.01f, 100.0f);
      }

      void CubeRenderer::setupVertexAttribs()
      {
          m_vbo->bind();
          m_program->enableAttributeArray(0);
          m_program->enableAttributeArray(1);
          m_context->functions()->glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, nullptr);
          m_context->functions()->glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0,
                                                        (const void *)(36 * 3 * sizeof(GLfloat)));
          m_vbo->release();
      }

      void CubeRenderer::render(QWindow *w, QOpenGLContext *share, uint texture)
      {
          if (!m_context)
              init(w, share);

          if (!m_context->makeCurrent(w))
              return;

          QOpenGLFunctions *f = m_context->functions();
          f->glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

          if (texture) {
              f->glBindTexture(GL_TEXTURE_2D, texture);
              f->glFrontFace(GL_CW); // because our cube's vertex data is such
              f->glEnable(GL_CULL_FACE);
              f->glEnable(GL_DEPTH_TEST);

              m_program->bind();
              QOpenGLVertexArrayObject::Binder vaoBinder(m_vao);
              // If VAOs are not supported, set the vertex attributes every time.
              if (!m_vao->isCreated())
                  setupVertexAttribs();

              static GLfloat angle = 0;
              QMatrix4x4 m;
              m.translate(0, 0, -2);
              m.rotate(90, 0, 0, 1);
              m.rotate(angle, 0.5, 1, 0);
              angle += 0.5f;

              m_program->setUniformValue(m_matrixLoc, m_proj * m);

              // Draw the cube.
              f->glDrawArrays(GL_TRIANGLES, 0, 36);
          }

          m_context->swapBuffers(w);
      }