Convert the 'populateQuaternion' function to 'quaternion' attribute

[pozdnyakov]

The attribute will be more convenient to use.

The main reason for the previous using of BYOB was the potential GC issues, now BYOB here seems to be unnecessary: w3c/sensors#153 (comment)

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[kenchris]

OK, we will probably want populate methods later though :) lgtm

[pozdnyakov]

OK, we will probably want populate methods later though :)

IMO populate still makes sense for matrices as matrix can contain translation data before calling populateMatrix, so that after the call the matrix will contain both translation and orientation.
For quaternions populate is useless.

[kenchris]

But are they? If it makes sense getting different quats in different shader instances, it would not be. I am not sure about those use-cases but they should cover some of the same as matrices

[pozdnyakov]

not sure I understood you correctly, what I mean is that matrix can contain both translation and rotation data (pls see example 5 at https://w3c.github.io/webvr/spec/latest/#interface-vrpose), so if translation elements are already predefined, populateMatrix call won't erase them but just introduce rotation data to the given matrix, this is quite convenient.

[alexshalamov]

lgtm. We can add populateMatrix(Float32Array or DOMMatrix) later. I wish DOMMatrix would expose Float32Array internal buffer, so it is easy and free to convert them back and forth, making them compatible with WebGL.

[alexshalamov]

@pozdnyakov We should also document that if transformation matrix that was provided to populateMatrix contains scaling / rotation, those values will be overwritten, only translation values would be kept intact.

[pozdnyakov]

Reverted this with 7d7f697 as exporting Float32Array as property makes the sensor data mutable