concave-hull | 易学教程

Alpha shapes in 3D

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问题 Is there an "alpha shape" function in 3 dimensions in python, other than the CGAL python bindings? Alternatively, is there a way to extend the example below into 3D? 2D example: draw a smooth polygon around data points in a scatter plot, in matplotlib I'm currently calculating volume using this ConvexHull example, but for my purposes the volumes are inflated due to the "convex" constraint. Thanks, 回答1: I wrote some code for finding alpha shape surface. I hope this helps. from scipy.spatial

Alpha shapes in 3D

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Python Concave Hull Polygon of a set of lines

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问题 I'm looking for a python implementation for the Concave Hull problem. My problem is a bit different since I don't have a set of points, but a set of lines, where the result Concave-Hull will roughly bound along the lines (as in the left drawing). I understand that there is no single "correct answer". But some approximation will be enough for my needs. One possible solution is to take each line and interpolate it to a range of let's say 20 points and find the concave hull of all the created

Algorithm to create minimal bounding-box composition of point cloud

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问题 I have a set of 2D points. I want to find a set of (possibly overlapping and arbitrarily oriented) bounding-boxes for subsets of these points such that each point lies within at least one box, each box contains at least k points and such that the combined area of the boxes is minimized. One idea for an algorithm I have is: use a concave-hull algorithm to find a concave hull for the points. use convex decomposition algorithm to find a set of convex hulls. compute arbitrarily oriented minimum

Connecting a set of points to get a non-self-intersecting non-convex polygon

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问题 I have an unordered set of 2D points which represents the corners of a building. I need to connect them to get the outline of the building. The points were obtained by combining different polygons collected by different individuals. My idea is to use these polygons to get the points in order (e.g. taking the region between the biggest and smallest polygons and connect the points such that it comes in this region). I tried using the minimum distance criteria and also to connect the points

Estimating an area of an image generated by a set of points (Alpha shapes??)

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问题 I have a set of points in an example ASCII file showing a 2D image. I would like to estimate the total area that these points are filling. There are some places inside this plane that are not filled by any point because these regions have been masked out. What I guess might be practical for estimating the area would be applying a concave hull or alpha shapes . I tried this approach to find an appropriate alpha value, and consequently estimate the area. from shapely.ops import cascaded_union,

Determine which points lay outside an irregularly-shaped data footprint in R?

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问题 I have a series of points in an area whose 'footprint' shape is highly irregular: I'd like to determine all of the coordinates within the footprint's vertices. The end goal is to determine which data points lay outside this footprint. Does anyone have an efficient way to go about doing this?? My best idea to approaching this is to draw a polygon based on the green area's vertices and then use said polygon's coordinates to determine 'outlier' points' (though, I'm not sure how to do that yet --

Boundary enclosing a given set of points

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问题 I am having a bit of a problem with an algorithm that I am currently using. I wanted it to make a boundary. Here is an example of the current behavior: Here is an MSPaint example of wanted behavior: Current code of Convex Hull in C#:https://hastebin.com/dudejesuja.cs So here are my questions: 1) Is this even possible? R: Yes 2) Is this even called Convex Hull? (I don't think so) R: Nope it is called boundary, link: https://www.mathworks.com/help/matlab/ref/boundary.html 3) Will this be less

Boundary enclosing a given set of points

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I am having a bit of a problem with an algorithm that I am currently using. I wanted it to make a boundary. Here is an example of the current behavior: Here is an MSPaint example of wanted behavior: Current code of Convex Hull in C#: https://hastebin.com/dudejesuja.cs So here are my questions: 1) Is this even possible? R: Yes 2) Is this even called Convex Hull? (I don't think so) R: Nope it is called boundary, link: https://www.mathworks.com/help/matlab/ref/boundary.html 3) Will this be less performance friendly than a conventional convex hull? R: Well as far as I researched it should be the

OpenCV - Concave hull

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问题 I am looking for an OpenCV implementation of a function to find the concave hull of a set of points (as for the convexHull function). Does anyone know of it? Here is an explanation: http://ubicomp.algoritmi.uminho.pt/local/concavehull.html Thank you in advance. 回答1: You can also use Growing Neural Gas algorithm. There are several implementations in web take a look at ( https://github.com/BelBES/libGNG ) for example. Video of the algorithm is here: http://www.youtube.com/watch?v=fVd4ly8wilY