We start our analysis from the object-coordinate system. This is the space where vertex coordinates are specified. If we want to translate or move objects around, we use a matrix that encodes these transformations. This matrix is known as the Model matrix. Once we multiply the vertices of our object by the Model matrix, we obtain new vertex coordinates. These new vertices will determine the position of the object in our 3D world.
In object coordinates, each object is free to define where its origin is and to specify where its vertices are with respect to this origin. In world coordinates, the origin is shared by all of the objects. World coordinates allow us to know where objects are located with respect to each other. It is with the model transform that we determine where the objects are in the 3D world:
