Render to a unsigned integer texture2D - opengl

Question

I am trying to render to an (RGBA32UI) unsigned-integer texture2D and then read pixel data using glReadPixels. But it does not work
GLuint FramebufferName = 0;
glGenFramebuffers(1, &FramebufferName);
glBindFramebuffer(GL_FRAMEBUFFER, FramebufferName);
// The texture we're going to render to
GLuint renderedTexture;
glGenTextures(1, &renderedTexture);
glBindTexture(GL_TEXTURE_2D, renderedTexture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB32UI, windowWidth, windowHeight, 0, GL_RGB_INTEGER, GL_UNSIGNED_INT, 0);
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_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, renderedTexture, 0);
// The depth buffer
GLuint depthrenderbuffer;
glGenRenderbuffers(1, &depthrenderbuffer);
glBindRenderbuffer(GL_RENDERBUFFER, depthrenderbuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, windowWidth, windowHeight);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthrenderbuffer);
GLenum DrawBuffers[1] = { GL_COLOR_ATTACHMENT0 };
glDrawBuffers(1, DrawBuffers); // "1" is the size of DrawBuffers
glBindFramebuffer(GL_FRAMEBUFFER, FramebufferName);
render_scene();
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glBindBuffer(GL_READ_BUFFER, FramebufferName);
glReadBuffer(GL_COLOR_ATTACHMENT0);
GLuint data[3];
for (int i=0; i < windowWidth; i++)
for (int j = 0; j < windowHeight; j++)
{
glReadPixels(i, j, 1, 1, GL_RGB32UI, GL_UNSIGNED_INT, data);
if (data[0] == 1 && data[1] == 2 && data[2] == 3)
int a = 1;
}
Shader (GLSL)
#version 450 core
out uvec3 output_color;
void main()
{
output_color = uvec3(1, 2, 3);
}
Is there anyone experienced this problem? Please, help me.

Answer 1

The command
glBindBuffer(GL_READ_BUFFER, FramebufferName);
is wrong. glBindBuffer does not have the target GL_READ_BUFFER, so this should result in an GL_INVALID_ENUM error. (You should really add some error checking, preferably via debug output if available.) You can never bind an FBO with glBindBuffer. FBOs can only be bound with glBindFramebuffer. What You actually wanted to do is:
glBindFramebuffer(GL_READ_FRAMEBUFFER, FramebufferName);
glReadBuffer(GL_COLOR_ATTACHMENT0);
Also note that glBindFramebuffer(GL_FRAMEBUFFER, ...); is just a shortcut to bind GL_DRAW_FRAMEBUFFER and GL_READ_FRAMEBUFFER at once.