randomVector3OnLine (attribute, index, start, end) {
        'use strict'
        const pos = start.clone()

        pos.lerp(end, Math.random())

        attribute.typedArray.setVec3Components(index, pos.x, pos.y, pos.z)
    }
Given an SPE.ShaderAttribute instance, and various other settings,
assign values to the attribute's array in a `vec3` format.

@param  {Object} attribute   The instance of SPE.ShaderAttribute to save the result to.
@param  {Number} index       The offset in the attribute's TypedArray to save the result from.
@param  {Object} start       THREE.Vector3 instance describing the start line position.
@param  {Object} end         THREE.Vector3 instance describing the end line position.