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sebhunt

opened on Aug 27, 2013

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PVector.angleBetween(PVector, PVector) returns 0 for 3D vectors whenever the x and y components of a parameter are both 0. For example:

PVector.angleBetween(new PVector(0,0,1), new PVector(1,0,0))

returns 0 instead of PI/2.

Looking at the source code, it seems clear what is wrong:

// We get NaN if we pass in a zero vector which can cause problems
// Zero seems like a reasonable angle between a (0,0) vector and something else
if (v1.x == 0 && v1.y == 0) return 0.0f;
if (v2.x == 0 && v2.y == 0) return 0.0f;

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1. shiffman commented on Aug 27, 2013

   

   shiffman

   on Aug 27, 2013

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   Thank you for the post.

   Certain methods, like heading() and angleBetween() are only relevant for 2D. In 3D, for example, we have to ask the question "heading along what axis?", "angle between relative to what axis?" I think I should make some updates to the reference to make this more clear. If you are looking for more sophisticated 3D math with vectors, check out toxiclibs geom package.

   (Also, I think you meant PVector.angleBetween(new PVector(0,0,1), new PVector(0,0,0)) FYI).
2. shiffman

   closed this as completedon Aug 27, 2013
3. sebhunt commented on Aug 27, 2013

   

   sebhunt

   on Aug 27, 2013

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   (Not sure if commenting on closed issues is frowned upon but..). Ok, I guess, if that's the intention. But the PVector source code that I was looking at (0219-2.0.1) looks very much like it was written with 3D vectors in mind; it uses dot-product and interprets "angle between" as meaning the angle in the plane defined by the given pair of vectors, which I think is pretty standard). And I think the code would work too, if only those first two lines that I quoted were amended to:

   if (v1.x == 0 && v1.y == 0 && v1.z == 0) return 0.0f;
   if (v2.x == 0 && v2.y == 0 && v2.z == 0) return 0.0f;
   

   (And I really did mean PVector.angleBetween(new PVector(0,0,1), new PVector(1,0,0)).)
4. shiffman commented on Aug 27, 2013

   

   shiffman

   on Aug 27, 2013

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   Ahhhhhhh, sorry, I read your post too quickly and had a knee-jerk 2D only reaction. I see what you are saying now. Let me go back and look at this more.
5. shiffman

   reopened this on Aug 27, 2013
6. ghost assigned

   shiffman

   on Aug 27, 2013
7. shiffman commented on Aug 29, 2013

   

   shiffman

   on Aug 29, 2013

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   Ok, this is now closed via c84a5a5
8. shiffman

   closed this as completedon Aug 29, 2013
9. Manindra29

   added a commit that references this issue on Oct 30, 2013

   Update PVector.java

   c84a5a5
10. davidfokkema

    added a commit that references this issue on Mar 23, 2014

    Update PVector.java

    682305b
11. github-actions commented on Jun 17, 2021

    

    github-actionsBot

    on Jun 17, 2021

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    This issue has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.
12. github-actions

    locked as resolved and limited conversation to collaborators on Jun 17, 2021

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