Le 05.11.2007 21:30, Grassblade nous fit lire :
> Le Forgeron <jgr### [at] freefr> wrote:
>> Le 04.11.2007 17:16, alphaQuad nous fit lire :
>>> the task:
>>> Area = abs(   (xB*yA - xA*yB)  + (xC*yB -x B*yC)+( xA*yC - xC*yA ) ) /2

>> Let's make a numerical application with A(0,-1) B(1,0) and C(0,1)
>>
>>  abs ( (-1 - 0) + (0 - 1) + ( 0 +1 ) ) /2 ---> abs ( -1 ) /2 --> 1/2
>> (wrong)
> I get ( (-1 - 0) + (0 - 1) + ( 0 + 0 ) ) /2= -1, which is correct.
>
Ok, my fault.

So, I let you with alphaQuad trying to generalize that to 3D.

And I will keep using length(crossproduct(B-A,C-A))/2.

-- 
The superior man understands what is right;
the inferior man understands what will sell.
-- Confucius

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