Blender Git Loki

quite a load is still hidden behind the define #ifdef _work_on_sb_solver
a glance to view is the "STU PID semi implicit euler"
most of the work to implement a semi implicit euler was done ..
now i am dealing with the tradeoffs between 'calculation time' which is quite expensive .. inverting a 0(n*n) sparse matrix /* once agian thanks to brecht for his work on making sparse matrices LU decomposition and evaluating inverses that easy*/ putting it into and cropping works pretty nice .. argh off topic again
...
while i spent a little time on reading recent papers i found :

1. control on springs needs to be split in pushing and pulling /* fabric pushes easy but pulls hard */
2. diagonals on 4-gons (in the current SB model) can be seen as shear .. thus need a contol to modify .. this commit wil add it
3. 2 nd order springs /*aka rigidity */ can focus on bending .. thus renaming 'em

i have no idea how i would provide backward compatiblity, but the spots i marked in code :)