2D image coordinate to 3D world coordinate using Depth Map

Question

Having the intrinsic and extrinsic matrices how does one transfer 2D image coordinate to 3D world coordinate using the depth map image? A similar problem was discussed here: 2D Coordinate to 3D world coordinate, but it assumes images are rectified which is not the case here. I have a problem formulating the equation for this.

p_camera.x      = (pixCoord.x - cx) / fx;
p_camera.y      = (pixCoord.y - cy) / fy;
p_camera.z      = depth;

p_camera.x      = -p_camera.x*p_camera.z;
p_camera.y      = -p_camera.y*p_camera.z;

P_world = R * (p_camera + T);