Appends the given transform to this one.
The concatenated transforms are applied as follows:
V' = other.ToTerrain * this.ToTerrain * V
V = this.ToModel * other.ToModel * V'
V is a point in model-space and
V' is a point in terrain-space.
Triggers all (re-)computations.
This method may be called repeatedly. It will only perform work when necessary.
Returns the affine transformation from model-space to terrain-space, (re-)computing it if necessary.
It is not necessary to call Compute before getting this property.