PVector.angleBetween() returns 0 for 3D vectors whenever x and y are both 0

[sebhunt]

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;

[shiffman]

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).

[sebhunt]

(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)).)

[shiffman]

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.

[shiffman]

Ok, this is now closed via c84a5a5

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