CGAL users discussion list

[Martin Baeker <>]

> I need to compute the angle between two vectors. I've got two Vector_3
> objects and I was thinking to compute their dot product and then divide
> this by the product of the magnitude of the two vectors. The problem is
> that I can't evaluate the sqrt of the sum of the squared components of
> the vectors. Is there an in-built function that computes the magnitude
> of a vector.

In principle, you shoul dbe able to calculate the sqrt. Make sure that
you convert your numbers to double:
sqrt(CGAL::to_double( X)).

Be aware, however, that you loose the arbitrary precision and enter
the irrational...


>  
> Another possibility would be using Direction_3, but it seems that there
> is no dot product defined for this object.
> Anyway, if I transform my vectors into Direction_3 objects and then I
> transform the Direction_3 objects into vector do I end up with unit
> vectors? In this case I could easily evaluate the dot product of these
> vectors and I have solved my problems.
> Thank You
> Angelo
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                   Institut für Werkstoffe
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