Tor Olav Kristensen wrote:
> "Tor Olav Kristensen" <tor### [at] TOBEREMOVEDgmailcom> wrote:
>> Jim Charter <jrc### [at] msncom> wrote:
>>> Can anyone show me proper usage of the Shear_Trans macro.
>>>
>>> This is a modification I made to the "Basic Scene" supplied on the
>>> insert menu.  Can't get it to parse.
>>>
>>> #local A=<1,2,3>;
>>> #local B=<1,2,3>;
>>> #local C=<1,2,3>;
>> ....
>>>    Shear_Trans(A,B,C)
>> ....
>>
>> Hi Jim,
>>
>> You have to make sure that no two of those three vectors are parallel.
>>
>> I.e.: These three conditions have to be met:
>>
>> vlength(vcross(A, B)) > 0
>> vlength(vcross(B, C)) > 0
>> vlength(vcross(C, A)) > 0
>>
>> (Note that there are also other ways to check for parallel vectors.)
> 
> I think the most elegant way is to use the scalar triple product:
> 
> vdot(A, vcross(B, C)) != 0
> 
> See:
> http://en.wikipedia.org/wiki/Triple_product
> 
> --
> Tor Olav
> http://subcube.com
> 
> 
> 
> 

Yes that *is* elegant.  Thank you, and Stephen

Post a reply to this message