From: François Duranleau (duranlef_at_[hidden])
Date: 2007-10-08 11:17:04
On Sun, 7 Oct 2007, Fernando Cacciola wrote:
>> Let's consider the example below.
>> [really bad code ommitted]
>> Translating this to gtl isotropic code:
>> concave += (a.towards(b).left() == b.towards(c));
> OK. So you are calling isotropic what I know as "coordinate free
> Notice that I could implement the above as:
> concave += ( cross_product((b-a),(c-a)) < 0 ) ;
> using basic algebraic stuff (and this would work for non-rectilinear edges
> as well).
>> convex += (a.towards(b).right() == b.towards(c));
> But using basic algebra that becomes:
> convex += ( cross_product((b-a),(c-a)) > 0 ) ;
Just one thing: in linear algebra, cross product returns a vector. Then
how can you compare that result with a scalar?
-- Francois Duranleau
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