int ForwardRenderer::read_buffer_id(const glm::vec2& coord)
{
    glBindFramebuffer(GL_FRAMEBUFFER, picking_buffer);
    glFlush();
    glFinish();
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    unsigned char data[4];
    glReadBuffer(GL_COLOR_ATTACHMENT0);
    glReadPixels(coord.x, coord.y, 1, 1, GL_RGBA, GL_UNSIGNED_BYTE, &data);
    glBindFramebuffer(GL_FRAMEBUFFER, 0);
    return data[0] + data[1] * 256 + data[2] * 256 * 256;
}