New API: add a scaled vector

[LeXXik]

Fixes #5114

Adds a new API to vectors: add a scaled vector. Adds a scaled vector to the current instance and returns itself as result. Does not modify the vector being added.

const vec = new pc.Vec3();
vec.addScaled(pc.Vec3.UP, 2); // [0, 2, 0]

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[willeastcott]

I guess my only slight hesitation is the naming of addScalar and addScaled....just wondering if that is the best option....

[LeXXik]

I've also considered addScaledVector, similar to threejs, but its too long for my taste, so I went with a shorter version. Suggestions welcome.

[marklundin]

I've seen addScaledVec and addScaledVector in other api's which is more descriptive and easier to distinguish against addScalar

[LeXXik]

Added a poll for voting #5707

[willeastcott]

@marklundin It does make it clearer. But at the same time, the VecX APIs are so terse/succinct. Looks down the API page and it's really very concise (and guessable, I'd argue). So I'd probably err on a short option over a longer one in this case. It's just the minor clash with addScalar that make me pause. I'm very, very torn.

[marklundin]

Yep agree, it's just that slight collision with addScalar that gives hesitation. However there's no real ambiguity what addScalar does, so maybe it's a non issue?

[willeastcott]

Yes, I guess so. @mvaligursky, thoughts?

[mvaligursky]

I'm happy with addScaled I think. even though my mind calls this mad from old shader assembly instruction (multiply and add), even though that instruction handles vector being multiplied by both scalar or another vector.

[willeastcott]

OK, agreed. Once that JSDoc is updated to number, we can merge.

[mvaligursky]

Thanks!