Talk:Signed distance function

Latest comment: 7 years ago by Hawkmoth-accent in topic Still dubious definition

Rather dubious definition edit

The definition seems rather dubious. If  , then   (as given in the definition of f) with   is always zero. Should probably be replaced with   instead? Additionally, I've never seen the definition defining the inside of   as positive, only the other way around. If no-one objects, I will make some edits in the next few days. 193.157.239.253 (talk) 10:16, 18 January 2016 (UTC)Reply

Still dubious definition edit

It seems that the sign chosen in this article for this distance function is the opposite as usual. This is the reason of adding a {{citation needed}} tag.

One strong reason for taking the opposite sign is that with the definition of the article, the signed distance is equal to the unsigned distance (minimum of the distance from a fixed point to a point in the set) only on the boundary. On the other hand, with the opposite sign, the two distances differ only in the interior. Moreover this definition contradicts the common intuition: for everybody, the distance from a point to a set is positive outside the set and needs a further convention inside the set. Who, except the author of this article would say that I am at a negative distance from the Moon? Similarly, the definition of this article would imply that the altitude of an aircraft would be negative, and the altitude of a submarine would be positive. Clearly the opposite of the usual conventions. D.Lazard (talk) 17:29, 25 April 2016 (UTC)Reply

You're giving preference to being outside the object. You could give the same argument the other way around: if I am sitting inside a room, the distance to the nearest wall (the boundary of the room) "should" be positive from my perspective. The truth is that it probably doesn't really matter, as long as the convention is understood, similar to say, choosing an origin. Although, there may be application dependent reasons for using one convention or the other. In any case, I've added two citations to illustrate the use of both conventions. Hawkmoth-accent (talk) 16:52, 27 May 2016 (UTC)Reply

Problem with the image of the duck edit

Hey Drummyfish (talk · contribs), there is one red circle inside the duck that is way to small, it's close to the neck.