It's a good idea to always name your matrices in a manner that explicitly states the source and destination coordinate systems. So rather than 'projection', 'view' and 'model' you'd have something like 'viewToClip', 'worldToView' and 'modelToView'. Then when you concatenate and invert matrices to create new ones, their names are self-explanatory as are their assumed inputs and outputs. It's quite easy to tell what a 'clipToWorld' matrix does. 'viewProjectionInverted' - not so much.