bug in ADAPTIVEFP branch about opengjk HOT 4 CLOSED

Yes, that's likely a bug, but:

1. I believe B[0] isn't right, although barely used because it represents the case when the latest vertex a is discarded - and that's never the case for GJK, but may be useful to develop for EPA.
2. I doubt you actually need to ADAPTIVEFP.

I'm not sure if I understand your question, what do you mean by "clamp that to [0,1] as the lambda"? Anyway, unless you can guarantee that all your simplices are not "degenerate", then you need the reduction stuff. The SV method is recursive, but specifically for a 1-simplex (line segment) the call to S1D leads to either of these cases: (i) The origin is between A and B or (ii) The origin is beyond A. Again, the origin cannot be found beyond B in GJK, but may be useful to develop for EPA.

from opengjk.

Thanks for the reply - I don't need the ADAPTIVEFP, but I was looking at that branch because it was easier to understand than the for -loop in the non-adaptive case!

As for the S1D stuff, consider the test of point b.
if x is dotProduct(b, t) / dotProduct(t, t)
then det_pb = (x * (ai - bi) + bi) - bi = x * (ai - bi)
so the sign test with ti (= bi-ai) is comparing the signs of x * (ai - bi) and -(ai - bi)

In other words, ai and bi make no difference, degenerate or not, to the sign check and you can just test for x < 0. And in the case of the origin being between A and B, x actually is the first lambda value.

Not sure if I've explained this properly or if I'm missing something?

Adrian

from opengjk.

You are right, there are a few unnecessary operations there: -bi, -1*. I believe the method would be equivalent but better coded - and better coding help presenting the method as well.

We have been working on a new, totally undocumented, method and for S1D things may work out like you said: first a dot product identifies the support of the point of minimum norm, then a second step computes the shortest vector.

from opengjk.

I won't do any work to fix the potential bug reported here, but I'll close this once I merge the dev branch into master as the new algorithm doesn't show this.

from opengjk.