matrix interpolation?

Hi,

I'm wondering if anyone knows how to interpolate between two matrices. It's not for rotation, but rather for the projection matrix, to create a smooth transition from a perspective view to an orthographic/isometric view.

I know it's possible because Maya does it, when clicking the small view gizmo thingy, but I have no idea how it's done.

Any hints?

A matrix, from math point of view is a base set of "unit vectors" for a given vector space.

So to interpolate between matrices, you interpolate between the vector spaces.

To do so you take the base vectors of this spaces (each column is one) and interpolate between them.

This should, at least theoretically, work.
I don't know how good thought, have never used it ... its just what I got tought in linear algebra :)