Initialize a set of engine morph targets and compress them to GPU friendly buffers. These morph targets are initialized from a set of deltas. Each morph target needs to have Model->GetNumBaseVerts() number of deltas. All deltas are concatenated in one big array. So all deltas of all vertices for the second morph target are appended to the deltas for the first morph target, etc. In other words, the layout is: [morph0_deltas][morph1_deltas][morph2_deltas][...].