Implementation of p5.Vector setHeading()

[samdelong]

I am opening a new issue to implement a setHeading method for the p5.Vector class. Currently, p5 contains a function rotate(), which rotates the vector by a certain value, but no such method exists for setting the vector's rotation to an explicit direction. I currently have something working, and am planning to pull request an implementation.

An implementation would look as follows:

p5.Vector.setHeading = function(angle){
  this.rotate(-this.heading())
  this.rotate(angle)
}

This is my first time attempting to contribue to open source, so any tips would be greatly appreciated!

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[mishazawa]

Hello.

no such method exists for setting the vector's rotation to an explicit direction

AFAIK: vector is object that have direction and length. By creating vector you already set his rotation that point to direction.

Take a look at fromAngle function. I think it doing exactly what you want.

Probably this operation may be cheaper (for CPU cycles) when you create new vector and rotate it. Because heading() calculates arctangent, rotate() calculates sine and cosine (for coordinates [x, y] that will be point to vector with 0 angle), then new rotation calculates sine and cosine again.

[samdelong]

Hi mishazawa

The issue with creating a new vector altogether with fromAngle() would be any user-defined characteristics of the vector would be erased. However I can see why my implementation would be poor practice for performance.

Perhaps we could copy the code from fromAngle(), but instead of returning a new vector, we just modify the vector in the current context?

[mishazawa]

any user-defined characteristics of the vector would be erased

Which ones? Vector has only [x, y, z] properties.
If you trying to store any other data inside vector f.e.:

let vec = createVector(1, 2, 3);
vec.offset = createVector(2, 2, 2);

I highly recommend not to do it. Because vector is designed to store only direction and length (through coordinates).
Instead you could create your own structure f.e.:

let arrow = {
  direction: createVector(1,2,3),
  offset: createVector(2, 2, 2),
}

we could copy the code from fromAngle()

Proper way is to create new vector. I don't see any use cases when you should modify vector instead just re-write it.

[samdelong]

I can see where you're coming from, but often times p5.js is used by beginners, and having to create a new vector using fromAngle() is pretty unintuitive. I think a setHeading() function would help ease some confusion. If not it's own implementation, an alias would still be helpful.

Also just to note, a vector's z property would be lost if using the fromAngle() function. Even though the heading() function should only be used on 2D vectors, it would be beneficial in reducing some confusion.

[burnedsap]

I agree, I think it would be handy to have a setHeading() function.

[samdelong]

As per @mishazawa s suggestion, I edited the setHeading() functions implementation to more closely represent the fromAngle() function, but without the need to create a new object. I still think this feature would improve the p5.js library.

[limzykenneth]

Thanks for the discussions! I'm ok with this being added, can someone else have a look at this proposal and if it's ok, we'll merge it? @lmccart @montoyamoraga @outofambit @stalgiag

[montoyamoraga]

i agree that this will be a good contribution to the library. My only doubt is if this would break any 3D vector? i saw on the docs that vectors can be x,yz too, right?

[samdelong]

I included that this method would only work for 2d vectors in the method documentation. Im not sure if something should prevent a user from rotating a 3d vector...maybe a console warning would be helpful here?