How to enable depth testing in QOpenGLFrameBufferObject

Leosunshine

I want to render the scene to a texture and the QOpenGLFrameBufferObject was used, but the depth testing was not work in the rendered texture, even if I bind the a depth render buffer to the FBO. It is all right if I render the scene to the screen.

#include "fbowidget.h"

FBOWidget::FBOWidget(QWidget *parent): QOpenGLWidget(parent), QOpenGLFunctions_3_3_Core()
{

}

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

vertex.create();
GLfloat v[] = {
    0,0,-0.5,
    0,0.5,-0.5,
    -0.5,0,-0.5,
    0,0,-1,
    0,1,-1,
    -1,0,-1,
};
vertex.bind();
vertex.allocate(v, 18 * sizeof(GLfloat));

this->program = new QOpenGLShaderProgram();
this->program->addShaderFromSourceFile(QOpenGLShader::Vertex, "v.glsl");
this->program->addShaderFromSourceFile(QOpenGLShader::Fragment, "f.glsl");
this->program->link();
this->program->bind();
this->vertexLocation = this->program->attributeLocation("aPosition");

rectVertex.create();
GLfloat rect[] = {
    -0.5, 0.5, -1,
    -0.5, -0.5, -1,
    0.5, -0.5, -1,
    -0.5, 0.5, -1,
    0.5, -0.5, -1,
    0.5, 0.5, -1
};
rectVertex.bind();
rectVertex.allocate(rect, 18 * sizeof(GLfloat));

this->rectProgram = new QOpenGLShaderProgram();
this->rectProgram->addShaderFromSourceFile(QOpenGLShader::Vertex, "vertex.glsl");
this->rectProgram->addShaderFromSourceFile(QOpenGLShader::Fragment, "fragment.glsl");
this->rectProgram->link();
this->rectProgram->bind();

this->rectVertexLocation = this->rectProgram->attributeLocation("aPosition");
glEnable(GL_DEPTH_TEST);
glEnable(GL_CULL_FACE);
this->fbo = new QOpenGLFramebufferObject(901,571);

glGenRenderbuffers(1, &this->depthTextureId);
glBindRenderbuffer(GL_RENDERBUFFER, this->depthTextureId);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, 901, 571);
this->fbo->bind();
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthTextureId);

}

void FBOWidget::resizeGL(int w, int h){
this->glViewport(0,0,w,h);
}

void FBOWidget::paintGL(){
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
glClearColor(1.0f,1.0f,0.0f,1.0f);
this->program->bind();
this->fbo->setAttachment(QOpenGLFramebufferObject::Depth);
this->fbo->setAttachment(QOpenGLFramebufferObject::NoAttachment);
this->fbo->bind();
glEnable(GL_DEPTH_TEST);
vertex.bind();
this->program->setAttributeBuffer(this->vertexLocation, GL_FLOAT, 0, 3, 0);
this->program->enableAttributeArray(this->vertexLocation);
glDrawArrays(GL_TRIANGLES, 0, 6);
glDisableVertexAttribArray(this->vertexLocation);
this->fbo->bindDefault();

glBindTexture(GL_TEXTURE_2D, this->fbo->texture());
this->fbo->toImage().save("hello.jpg");
this->rectProgram->bind();

rectVertex.bind();
this->rectProgram->setAttributeBuffer(this->rectVertexLocation, GL_FLOAT, 0, 3, 0);
this->rectProgram->enableAttributeArray(this->rectVertexLocation);

glDrawArrays(GL_TRIANGLES, 0, 6);
glDisableVertexAttribArray(this->rectVertexLocation);

}