Area inside a closed curve
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I have generated a surface on a 3d plot and have created a 2d curve (closed loop) somewhere on the surface. How to identify the x-, y-coordinates (z-coordinates for all points lying on and inside the curve are same) lying inside the curve? This is somewhat similar to the 'Fill Color' command in MS Paint.
Edit: The curve is a plot of various discrete points.
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Answers (2)
Image Analyst
on 13 Jan 2014
Pass the planar coordinates into polyarea().
2 Comments
Roger Stafford
on 13 Jan 2014
If the surface bounded by the closed curve is not planar, then "polyarea" will not be very accurate. It would be necessary to do a closely-spaced triangulation of this enclosed surface area and sum the area of the triangles as an approximation.
Image Analyst
on 13 Jan 2014
Right - I thought of that. I wasn't sure how Amit was going to ensure that the curve on the 3D surface lies in a plane (constant z value) but I assume he has some way. Probably not a good assumption.
Roger Stafford
on 13 Jan 2014
Sahil, if your surface is determined by some equation f(x,y,z) = 0, and if the boundary curve on this surface is determined by another function g(x,y,z) = c for some constant c, then it is likely that points on the surface which are inside the curve satisfy either g(x,y,z) < c or else g(x,y,z) > c. If so, this should furnish you the information you need for a closely-spaced set of points throughout the surface inside the curve to allow you to generate a triangulation of them so as to compute a good approximation for the surface area enclosed.
2 Comments
Image Analyst
on 13 Jan 2014
Are you saying that you can't use polyarea() for that case for some reason?
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