For anyone interested in how adding zero to a bad zero can make a better zero. LOL...

https://en.wikipedia.org/wiki/Signed_zero

Seems right to me, unless there’s a case I can’t think of where negative zero is needed?

In D4795#109560, @William Reynish (billreynish) wrote:

Seems right to me, unless there’s a case I can’t think of where negative zero is needed?

Mathematically the zeros are the same number, so I doubt it. Besides, this is only for display. But it is really because of that uncertainty in many people that we need to not show it.

The topic was so cool to look into.

Hi peeps.

I've got a question about this.

I'm not a fan of negative zero as I have found it to cause issues when exporting armature animations (and sometimes within Blender itself).

Last year we did a small game project at CGCookie and when troubleshooting a weird flipping error I found that if I turned off x-mirror and manually changed the -0.0 to 0.0 on the bones, the flipping was gone in Unity.
If this patch only changes the way the number is displayed and not the underlying value I never would have been able to find the cause of the issue.

So here's my question. Is it wise for it to only change the way it displays the value?

If -zero and +zero are mathematically the same, can't the underlying value be changed instead of the way it is displayed?

@Wayne Dixon (waylow) : I found that if I turned off x-mirror and manually changed the -0.0 to 0.0 on the bones, the flipping was gone in Unity.

Holy crap. Although positive and negative zero are mathematically identical, I can certainly see that there could be parsing errors if those are exported and are not expected. You just don't expect a "-" for zero.

If this patch only changes the way the number is displayed and not the underlying value I never would have been able to find the cause of the issue.
...can't the underlying value be changed instead of the way it is displayed?

Great question. Until you mentioned this I would have never guessed that this value was anything more than a confusion for people.

I imagine that @Brecht Van Lommel (brecht) will probably notice this ticket and your comment and will weigh in. And we can leave this the way it is, or do something different or better.

It's not possible to avoid -0.0 in general in an efficient way. It's just how floating point math works in C and Python and we can't possibly eliminate it everywhere.

Exporters could avoid writing -0.0, but that needs to be fixed in each exporter. If -0.0 causes in exported files causes issue in Unity, I would also consider that a bug in Unity. But it's also possible that -0.0 actually meant it was -0.0000000001, or that there is a bug in the exporter with handling of -0.0. In any case, that's for its own bug report and there is no general solution for it.

@Brecht Van Lommel (brecht) Just to be clear, this patch is fine right? Since this is just building the draw string.

It would be nice to commit it if so.

The functionality is fine with me, if you've tested that it works well you can commit.