AntonioMartini wrote:they are not the same line by line, the Baraff algorithm doesn't allow for low and hi force limits. Motors and Friction require such force limits in the karma solver(or ODE's direct solver).
With all due respect I do not think you completely understand what you are talking about. Motors and limits has nothing to do with teh underline matehematical algorithm.
Danzig and Lenkel methods both allowed for up and downs limits.
David Baraff was derived to handle specifically contacts, in that case the lower limit is zero and you do not need the code. In his paper he explain how to extend it to handle bilateral constraint. So adding the complement part to check the lower limit is not an invention.
It is okay because no one really takes that seriously as the method is a 0(n4) time complexity.
AntonioMartini wrote:
regarding the Richard's patent, the optimisations exploit the structure of the problem and so they are specific to rigid body dynamics. They allow
to reduce the memory footprint and speedup the algorithm compared to a standard PGS implementation. I think we can all appreciate the algorithm, the main point is if it can be legally considered an invention and if we morally agree on the overall patenting approach.
to be more specific the PGS patent has been filed on March 8, 2004.
was quickstep already in ODE at that time? were those optimisations already available in some form elsewhere?
http://cvs.sourceforge.net/viewcvs.py/o ... 8&view=log
the first version of quickstep is dated:
Tue May 18 18:12:30 2004 UTC (19 months, 2 weeks ago) by russ_smith
About Richard Tongue he is claiming the invention of storing J and JM into and indexed flat array. This is not an invention I had been using that as early as 1999. And I am not claiming an invention. I do not think anybody is.
Did you know that long before ODE realizes this could be done that way there were other engines doing the same publicly. I did it in Newton.
Or you also think that My solve is a copy of ODE like the stablishment hint in many circles.
In a nut shell this is what he is claimimg in three lines of symbolic math:
J A? J? * X = b can be executed by using a temp variable
Y = J? X
J * A? * Y = b
And that by the particular properties of Gauss Siddel the J * Y and J * A? Y can be done
with a recurrent formulations, by keeping Y as intermediate variable.
Let me tell you a secret lots of people are doing that for so many years.
Further more I discussed this same topic with Richard Tonge, Manju Edge and Mike Skololone (all from from AGIA) in May 2004 when they invited me to a meeting to discussed the possibility of using Newton with theirs vector coprocessor. In reality what they wanted was to fighure out what do I do to get my solver stable.
In the meeting I quickly realized the situation and I quickly exposed the exact about equations. He was in oh that I knew that.
It is not that I am and expert but I can hold my own with Math and Physics and this letlte twist may fool and untrained eye belief me it does nto fool me.
Following that reasoning I thing I can have 5 or 6 patents with Newton.
BTW in the meeting at AGIA I said I pass, I was not going to surrender Newton for then to dissect for free.
And truth me Newton is 100% correct LCP solver (with is the limitation of round off numerical precision and condition number below 10000 in single presistion numbers)