On Thu, Jun 16, 2011 at 11:59 PM, Luc Maisonobe <Luc.Maisonobe@free.fr> wrote:
> Le 16/06/2011 21:43, Curtis Jensen a écrit :
>>
>> On Wed, Jun 15, 2011 at 12:01 PM, Luc Maisonobe<Luc.Maisonobe@free.fr>
>> wrote:
>>>
>>> Le 15/06/2011 19:57, Curtis Jensen a écrit :
>>>>
>>>> The Vector2D and Vector3D classes have dotProduct and crossProduct
>>>> methods. I assume this is done be considering each vector originating
>>>
>>> There is no crossProduct in Vector2D in the current version I think.
>>>
>>
>> You are correct. It was sloppy typing on my part to include
>> crossProduct with Vector2D.
>>
>>>> from the origin. How can the dot product and cross products be
>>>> calculated for vectors not centered at the origin?
>>>
>>> Yes, these methods are intended for vectorial spaces, not affine spaces,
>>> which implies they work for vector centered at origin.
>>>
>>> We discussed on the dev list about having separate classes for
>>> Affine/Vectorial spaces and finally decided to merge everything in only
>>> one
>>> class per dimension. This is a classical choice and the user often
>>> already
>>> know what his instances represent.
>>>
>>
>> What is the suggested way of getting the dot and cross products for
>> vectors not centered at the origin? ie. the dot product of a corner
>> of a polygon.
>
> Something along these lines:
>
> Vector3D edge12 = vertex2.subtract(vertex1);
> Vector3D egge23 = vertex3.subtract(vertex2);
> double dot = edge12.dotProduct(edge23);
>
Ah yes; thanks.

Curtis
> Luc
>
>>
>> Thanks,
>> Curtis
>>
>>> Luc
>>>
>>>>
>>>> Thanks,
>>>> Curtis

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