Transform point using localToSceneTransform
Pedro Duque Vieira
pedro.duquevieira at gmail.com
Wed Jul 25 19:22:49 PDT 2012
> Hi Pavel,
> You claim that we need to add new methods if we treat a point as if it
> were a vector, but we would have to do that anyway to add methods that
> take vector.
> So, we can either add:
> transform(Vector) - treats its arg as magnitudes
> (and thus does a delta transform)
> or we can add:
> deltaTransform(Point) - delta transforms the arg
> (which is what you want to do with magnitudes)
There is a miss conception here. The proposed Vector isn't merely a
representation of a magnitude, it is a magnitude and an
angle/direction(although this is not stored internally in the instance) as
what exists in java3d and has a set of methods to compute/get vector
related stuff: get vector angle, get vector magnitude, get angle between 2
vectors, compute cross product between vectors, etc.
It isn't strictly necessary to do a deltaTransform to transform a Vector,
one can transform a vector like a point is transformed.
> It's a matter of whether the semantics are in the method name or the
> argument type.
> Furthermore, an array of doubles does not have an "am I a set of points
> or vectors" type attached to it so we do need to have 2 different method
> names for the methods that take arrays of doubles, whether or not we
> create a Vector class (whose sole purpose is to indicate that its values
> which are identical in nature to the Point class are to be considered as
If you use homogeneous coordinates notation, than an array of doubles
representing the vector will tell you that in fact it is a vector cause the
last value will be 0 (in contrast to a point which is 1).
> We can either encapsulate this information in a new class and add lots
> of methods for that new class, or we can encapsulate the information on
> the naming and documentation of new methods which use old types - both
> have equal expense in terms of method counts...
Thanks, best regards,
Pedro Duque Vieira
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