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);
 }