On Monday, 7 December 2020 at 13:54:26 UTC, Ola Fosheim Grostad
wrote:
On Monday, 7 December 2020 at 13:48:51 UTC, jmh530 wrote:
On Monday, 7 December 2020 at 13:41:17 UTC, Ola Fosheim
Grostad wrote:
On Monday, 7 December 2020 at 13:17:47 UTC, jmh530 wrote:
[snip]
"no need to calculate inverse matrix" What? Since when?
I dont know what he meant in this context, but a common
technique in computer graphics is to build the inverse as as
you apply computations.
Ah, well if you have a small matrix, then it's not so hard to
calculate the inverse anyway.
It is an optimization, maybe also for accuracy, dunno.
So, instead of ending up with a transform from coordinate
system A to B, you also get the transform from B to A for
cheap. This may matter when the next step is to go from B to
C... And so on...
A good example is a Simplex method for linear programming. It can
be done such as you have to calculate inverse [m x m] matrix
every step. Better, make a transform from one inverse matrix to
another, that speeds up algorithm from O(3) to O(2) and even
more. You don't even need to calculate the first inverse matrix
if the algorithm is built in such a way that it is trivial. It is
just one example.
