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| alexis chaigneau 2006-10-31, 7:11 pm |
| Hi,
I have a non-closed contour (for example a streamline...) and I would
like to compute the envelope of this contour.
Is anybody knows how to compute a curve-envelope ?
Thank you,
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| Roger Stafford 2006-10-31, 7:11 pm |
| In article <ef44f3d.-1@webcrossing.raydaftYaTP>, "alexis chaigneau"
<achaigneau@imarpe.gob.pe> wrote:
> Hi,
>
> I have a non-closed contour (for example a streamline...) and I would
> like to compute the envelope of this contour.
> Is anybody knows how to compute a curve-envelope ?
>
> Thank you,
---------------------
As far as I am aware, an evelope is only defined for a family of
curves. One example of this would be the family of normal lines to a
given curve. What family did you have in mind?
Roger Stafford
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| alexis chaigneau 2006-10-31, 7:11 pm |
| Roger,
Maybe the terms "envelope" is mathematically incorrect.
If a streamline has a spiral-form I would like to compute only the
outer "circle" (or outer contour without all the spiral).
e.g: I just would like to see the outer part of the snail's shell !!
> As far as I am aware, an evelope is only defined for a family of
> curves. One example of this would be the family of normal lines to
> a
> given curve. What family did you have in mind?
>
> Roger Stafford
>
| |
| Roger Stafford 2006-10-31, 7:11 pm |
| In article <ef44f3d.1@webcrossing.raydaftYaTP>, "alexis chaigneau"
<achaigneau@imarpe.gob.pe> wrote:
> Roger,
>
> Maybe the terms "envelope" is mathematically incorrect.
> If a streamline has a spiral-form I would like to compute only the
> outer "circle" (or outer contour without all the spiral).
> e.g: I just would like to see the outer part of the snail's shell !!
--------------------
It sounds as if you are talking about the convex hull of a curve. For
that you need matlab's 'convhull' function. If x and y are vectors
defining points on your curve, 'convhull' returns indices into x and y
indicating those that lie on the boundary of the convex hull, and this
would allow you to plot just those points. The interior points of your
"spiral" would disappear.
Roger Stafford
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