## How to augment our reality

Now that we know how to track planar objects, let's see how to overlay 3D objects on top of the real world. The objects are 3D but the video on our screen is 2D. So, the first step here is to understand how to map those 3D objects to 2D surfaces so that they look realistic. We just need to project those 3D points onto planar surfaces.

### Mapping coordinates from 3D to 2D

Once we estimate the pose, we project the points from 3D to 2D. Consider the following image:

As we can see here, the TV remote control is a 3D object but we are seeing it on a 2D plane. Now if we move it around, it will look like this:

This 3D object is still on a 2D plane. The object has moved to a different location and the distance from the camera has changed as well. How do we compute these coordinates? We need a mechanism to map this 3D object onto the 2D surface. This is where 3D-to-2D projection becomes really important.

We just need to estimate the initial camera pose to start with. Now, let's...