Fix/issue 1183 get distance measure

[barendgehrels]

Fixes #1183

The get_distance_measure (which I introduced some years ago, it's not used much) is not reliable for large values and subtle changes. I have to verify other usages too.

For the reported bug, where two segments are equal and the next are nearly equal, we could just use the side value (I don't remember why it was not like that earlier). It also makes that part of the code simpler. The verify_side constant is not necessary either.

Visual image of the problem:
(green and blue are the two input polygons, red/green outline is union)
It took the wrong continuation after two segments are equal.

[barendgehrels]

The added unit test for get_distance_measure (with a case of the fixed issue) output is below.
For float, it's always wrong for these values.
For double, it's wrong incidentally.
The side_by_triangle and side_robust always agree for these points.

float

 simplex_coll f 0 0 0 0
 simplex_left f 0.10000002384185791016 1 1 1
 simplex_right f -0.10000002384185791016 -1 -1 -1
 issue_1183_p f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_q f 0 0 0 0
 issue_1183_-5 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_-4 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_-3 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_-2 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_-1 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_0 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_1 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_2 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_3 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_4 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_5 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_6 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_7 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_8 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_9 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_10 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_11 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_12 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_13 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_14 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_15 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_16 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_17 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_18 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_19 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_20 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_250 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_251 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_252 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_253 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_254 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_255 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_256 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_257 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_258 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_259 f 16 1 -1 -1 [*** DM WRONG]
 issue_1183_260 f 16 1 -1 -1 [*** DM WRONG]

double

 simplex_coll d 0 0 0 0
 simplex_left d 0.099999999999999977796 1 1 1
 simplex_right d -0.10000000000000008882 -1 -1 -1
 issue_1183_p d 2.98023223876953125e-08 1 1 1
 issue_1183_q d 0 0 0 0
 issue_1183_-5 d 5.9604644775390625e-08 1 1 1
 issue_1183_-4 d 5.9604644775390625e-08 1 1 1
 issue_1183_-3 d 2.98023223876953125e-08 1 1 1
 issue_1183_-2 d 2.98023223876953125e-08 1 1 1
 issue_1183_-1 d 2.98023223876953125e-08 1 1 1
 issue_1183_0 d 2.98023223876953125e-08 1 1 1
 issue_1183_1 d 2.98023223876953125e-08 1 1 1
 issue_1183_2 d 2.98023223876953125e-08 1 1 1
 issue_1183_3 d 2.98023223876953125e-08 1 -1 -1 [*** DM WRONG]
 issue_1183_4 d 2.98023223876953125e-08 1 -1 -1 [*** DM WRONG]
 issue_1183_5 d 0 0 -1 -1 [*** DM WRONG]
 issue_1183_6 d 0 0 -1 -1 [*** DM WRONG]
 issue_1183_7 d 0 0 -1 -1 [*** DM WRONG]
 issue_1183_8 d 0 0 -1 -1 [*** DM WRONG]
 issue_1183_9 d 0 0 -1 -1 [*** DM WRONG]
 issue_1183_10 d 0 0 -1 -1 [*** DM WRONG]
 issue_1183_11 d 0 0 -1 -1 [*** DM WRONG]
 issue_1183_12 d 0 0 -1 -1 [*** DM WRONG]
 issue_1183_13 d -2.98023223876953125e-08 -1 -1 -1
 issue_1183_14 d -2.98023223876953125e-08 -1 -1 -1
 issue_1183_15 d -2.98023223876953125e-08 -1 -1 -1
 issue_1183_16 d -2.98023223876953125e-08 -1 -1 -1
 issue_1183_17 d -2.98023223876953125e-08 -1 -1 -1
 issue_1183_18 d -2.98023223876953125e-08 -1 -1 -1
 issue_1183_19 d -2.98023223876953125e-08 -1 -1 -1
 issue_1183_20 d -2.98023223876953125e-08 -1 -1 -1
 issue_1183_250 d 2.98023223876953125e-08 1 1 1
 issue_1183_251 d 2.98023223876953125e-08 1 1 1
 issue_1183_252 d 2.98023223876953125e-08 1 1 1
 issue_1183_253 d 2.98023223876953125e-08 1 1 1
 issue_1183_254 d 2.98023223876953125e-08 1 1 1
 issue_1183_255 d 2.98023223876953125e-08 1 1 1
 issue_1183_256 d 2.98023223876953125e-08 1 1 1
 issue_1183_257 d 2.98023223876953125e-08 1 1 1
 issue_1183_258 d 2.98023223876953125e-08 1 1 1
 issue_1183_259 d 2.98023223876953125e-08 1 1 1
 issue_1183_260 d 2.98023223876953125e-08 1 1 1

long double

 simplex_coll e 0 0 0 0
 simplex_left e 0.099999999999999977796 1 1 1
 simplex_right e -0.10000000000000008882 -1 -1 -1
 issue_1183_p e 9.1240508481860160828e-09 1 1 1
 issue_1183_q e 0 0 0 0
 issue_1183_-5 e 2.7503119781613349915e-08 1 1 1
 issue_1183_-4 e 2.3836037144064903259e-08 1 1 1
 issue_1183_-3 e 2.0154402591288089752e-08 1 1 1
 issue_1183_-2 e 1.6472768038511276245e-08 1 1 1
 issue_1183_-1 e 1.280568540096282959e-08 1 1 1
 issue_1183_0 e 9.1240508481860160828e-09 1 1 1
 issue_1183_1 e 5.4424162954092025757e-09 1 1 1
 issue_1183_2 e 1.7753336578607559204e-09 1 1 1
 issue_1183_3 e -1.9063008949160575867e-09 -1 -1 -1
 issue_1183_4 e -5.5879354476928710938e-09 -1 -1 -1
 issue_1183_5 e -9.255018085241317749e-09 -1 -1 -1
 issue_1183_6 e -1.2936652638018131256e-08 -1 -1 -1
 issue_1183_7 e -1.6618287190794944763e-08 -1 -1 -1
 issue_1183_8 e -2.0285369828343391418e-08 -1 -1 -1
 issue_1183_9 e -2.3967004381120204926e-08 -1 -1 -1
 issue_1183_10 e -2.7648638933897018433e-08 -1 -1 -1
 issue_1183_11 e -3.1315721571445465088e-08 -1 -1 -1
 issue_1183_12 e -3.4997356124222278595e-08 -1 -1 -1
 issue_1183_13 e -3.866443876177072525e-08 -1 -1 -1
 issue_1183_14 e -4.2346073314547538757e-08 -1 -1 -1
 issue_1183_15 e -4.6027707867324352264e-08 -1 -1 -1
 issue_1183_16 e -4.969479050487279892e-08 -1 -1 -1
 issue_1183_17 e -5.3376425057649612427e-08 -1 -1 -1
 issue_1183_18 e -5.7058059610426425934e-08 -1 -1 -1
 issue_1183_19 e -6.0725142247974872589e-08 -1 -1 -1
 issue_1183_20 e -6.4406776800751686096e-08 -1 -1 -1
 issue_1183_250 e 9.1240508481860160828e-09 1 1 1
 issue_1183_251 e 9.1240508481860160828e-09 1 1 1
 issue_1183_252 e 9.1240508481860160828e-09 1 1 1
 issue_1183_253 e 9.1240508481860160828e-09 1 1 1
 issue_1183_254 e 9.1240508481860160828e-09 1 1 1
 issue_1183_255 e 9.1240508481860160828e-09 1 1 1
 issue_1183_256 e 9.1240508481860160828e-09 1 1 1
 issue_1183_257 e 9.1240508481860160828e-09 1 1 1
 issue_1183_258 e 9.1240508481860160828e-09 1 1 1
 issue_1183_259 e 9.1240508481860160828e-09 1 1 1
 issue_1183_260 e 9.1240508481860160828e-09 1 1 1

[vissarion]

Thanks!

My understanding is that replacing distance_measure with side computation (side_by_triange seems to have enough accuracy for the tested use cases) resolves the issue.

Is it possible that other issues can be fixed by replacing distance_measure everywhere in the library? Seems redundant (and also fault sensitive).

[barendgehrels]

Thanks!

My understanding is that replacing distance_measure with side computation (side_by_triange seems to have enough accuracy for the tested use cases) resolves the issue.

Is it possible that other issues can be fixed by replacing distance_measure everywhere in the library? Seems redundant (and also fault sensitive).

Yes, we should deprecate this get_distance_measure indeed (or re-implemented using normal sides).
Preferably using failing cases but I don't have them.

I first found out that it was more precise, and in some cases it was - but in other cases, it's less precise so it shouldn't been used.
It is relatively new so there are not yet a lot of usages.