Full Source Code of initRenderToDepthTexture()

main.cpp

void initRenderToDepthTexture()
{    
    // Generate the depth texture ID
    glGenTextures(1, &depthTex);
    glBindTexture(GL_TEXTURE_2D, depthTex);
    
    // set texture size and format, high resolution 24bit for depth
    glTexStorage2D(GL_TEXTURE_2D, 1, GL_DEPTH_COMPONENT24, shadowMapWidth, shadowMapHeight);

    // set Interpolation and Out-of-range texture parameters
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); 
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);  

    // Assign the depth buffer texture to texture channel 1
    glActiveTexture(GL_TEXTURE1);
    glBindTexture(GL_TEXTURE_2D, depthTex);

    // Render to Texture
    // Create and set up the FBO
    glGenFramebuffers(1, &shadowFBO);
    glBindFramebuffer(GL_FRAMEBUFFER, shadowFBO);

    // use the depth texture as the framebuffer
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT,
                           GL_TEXTURE_2D, depthTex, 0);
                           
    glDrawBuffer(GL_NONE);

    GLenum result = glCheckFramebufferStatus(GL_FRAMEBUFFER);
    if( result == GL_FRAMEBUFFER_COMPLETE) {
        printf("Framebuffer is complete.\n");
    } else {
        printf("Framebuffer is not complete.\n");
    }

    glBindFramebuffer(GL_FRAMEBUFFER,0);
}