Drexel dragonThe Math ForumDonate to the Math Forum



Search All of the Math Forum:

Views expressed in these public forums are not endorsed by Drexel University or The Math Forum.


Math Forum » Discussions » sci.math.* » sci.math.num-analysis.independent

Topic: Calculating the area of a closed 3-D path or ring
Replies: 23   Last Post: Mar 25, 2013 4:54 PM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
fom

Posts: 1,968
Registered: 12/4/12
Re: Calculating the area of a closed 3-D path or ring
Posted: Mar 16, 2013 3:33 AM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

On 3/16/2013 2:27 AM, Ray Koopman wrote:
> On Mar 14, 9:36 pm, Math Guy <M...@Guy.com> wrote:
>> Ray Koopman wrote:
>>>
>>> You haven't said whether the ordering of the points around the
>>> loop is given or not.

>>
>> The user will specify the markers to be used (there are other markers
>> on the heart which will not be involved in this ring). A routine will
>> identify the order by picking one point and then determine which of
>> the remaining points is closest, and will piece-wise work it's way
>> around the ring. This should avoid any errors if the user gives the
>> order incorrectly.
>>

>>> Also, what do you want to do if the loop is not convex?
>>
>> Do you mean what if the loop looks like a potato chip with a bite taken
>> out of it?
>>
>> I don't see how that would affect the proposed area calculation method.

>
> It won't affect the plane of best fit, but it may make it harder to
> identify the loop. I would give the 2D coordinates to a convex hull
> routine. If the hull uses all the points then it's your loop. But
> if some points are inside the hull then a simple nearest-neighbor
> approach can sometimes connect the points in the wrong order.
>


Absolutely.

When I had been trying to visualize the stated problem,
I assumed that a "ring" would be a convex star.

Good point!





Date Subject Author
3/12/13
Read Calculating the area of a closed 3-D path or ring
Math Guy
3/13/13
Read Re: Calculating the area of a closed 3-D path or ring
Ray Koopman
3/13/13
Read Re: Calculating the area of a closed 3-D path or ring
Nicolas Neuss
3/13/13
Read Re: Calculating the area of a closed 3-D path or ring
Peter Spellucci
3/13/13
Read Re: Calculating the area of a closed 3-D path or ring
Shmuel (Seymour J.) Metz
3/13/13
Read Re: Calculating the area of a closed 3-D path or ring
Frederick Williams
3/13/13
Read Re: Calculating the area of a closed 3-D path or ring
Brian Q. Hutchings
3/14/13
Read Re: Calculating the area of a closed 3-D path or ring
fom
3/14/13
Read Re: Calculating the area of a closed 3-D path or ring
fom
3/14/13
Read Re: Calculating the area of a closed 3-D path or ring
Math Guy
3/15/13
Read Re: Calculating the area of a closed 3-D path or ring
Ray Koopman
3/15/13
Read Re: Calculating the area of a closed 3-D path or ring
Math Guy
3/15/13
Read Re: Calculating the area of a closed 3-D path or ring
fom
3/16/13
Read Re: Calculating the area of a closed 3-D path or ring
Ray Koopman
3/16/13
Read Re: Calculating the area of a closed 3-D path or ring
fom
3/16/13
Read Re: Calculating the area of a closed 3-D path or ring
Math Guy
3/16/13
Read Re: Calculating the area of a closed 3-D path or ring
fom
3/16/13
Read Re: Calculating the area of a closed 3-D path or ring
Ray Koopman
3/15/13
Read Re: Calculating the area of a closed 3-D path or ring
Peter Spellucci
3/16/13
Read Re: Calculating the area of a closed 3-D path or ring
Math Guy
3/17/13
Read Re: Calculating the area of a closed 3-D path or ring
Ray Koopman
3/17/13
Read Re: Calculating the area of a closed 3-D path or ring
Math Guy
3/18/13
Read Re: Calculating the area of a closed 3-D path or ring
Ray Koopman
3/25/13
Read Re: Calculating the area of a closed 3-D path or ring
Gib Bogle

Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© Drexel University 1994-2014. All Rights Reserved.
The Math Forum is a research and educational enterprise of the Drexel University School of Education.