In 2D, I implemented a Python concave hull algo using this representation: half-edge data structure. First of all you are to choose a representation for your mesh. Language English. By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy, 2020 Stack Exchange, Inc. user contributions under cc by-sa. Edit Now I see that you just want a polygon. is that possible in R? Perhaps you need to define 'best'. The Voronoi regions of the points on the boundary will tend to be either infinite or much longer than the ones on the interior. We found out that the convex decomposition algorithm is quite sensible to the scale of the mesh. So the algortihm is sometimes slow, but robust. In an older Unity version I just added a Mesh Collider with the flag "trigger" set and it worked perfectly. More Unity Games & Projects. But in some cases this algorthm is fast if not all points are on the convex hull. Then the red outline shows the final convex hull. Now the problem remains, how to find the convex hull for the left and right half. The AR-Toolkit is a Unity toolkit created by Stefan Volkers to create Augmented Reality Projection Games. This is the simplest convex hull algorithm, but will it also take the longest time to generate the convex hull? The 2D case is discussed in some detail here. 5 A convex hull of a set of points is the uniquely defined shape that minimizes the area that contain all the points, without having any angle that exceed 180 degrees between two neighbouring edges, as seen in Figure 2.1a. Concave hull generator. I already found several Java, Python and C++ implementation but no C# version. There's always tradeoffs. Given: n points that are strongly correlated to a 3d k-sided non-convex polygon, where n >> k, Find: the best fit concave-hull that matches the original geometry of the points. It sounds like you want to compute the concave hull of a collection of points in 3-space projected onto a plane. This defines a concave volume. Click here to upload your image
Calculating the concave hull was really expensive, and since I could now distinguish multiple objects, the concave algorithm became a bit unnecessary. First of all you are to choose a representation for your mesh. Dear friends, Do you know how to calculate the CONCAVE hull of a set of points (2- dimensional or n-dimensional)? How do you know if you have passed a waypoint? You also need an algorithm to figure out if a point is to the left, to the right, or on the same line as 2 other points. The larger the threshold, the closer the resulting polygon will be to the Convex Hull. Unity is the ultimate game development platform. unity.com; Version: 2019.4. You can also provide a link from the web. To know if two points are on the convex hull, we have to check all other points and make sure none of them are to the right of a line between the two points. Share. This point is always on the convex hull. To find a "concave hull" around a set of 3D points, I found that using the marching cube algorithm for volumetric data works best. My question is, is there a better way to approach this problem? By using our site, you acknowledge that you have read and understand our Cookie Policy, Privacy Policy, and our Terms of Service. Active 4 years, 6 months ago. The above approach works, but it is probably best to do it in two steps. In older versions of Unity there’s simply a tickbox to “Inflate Mesh” on mesh colliders. And with just one click! In 2D, I implemented a Python concave hull algo using this representation: half-edge data structure. (With a "smoothing" parameter of course). Concave Hull Generator Standard Triplanar Toon Standard Toony Standard Standardize Bows Standard Assets Example. Project the points onto a plane (This is pretty much what you have been doing) then compute the 2d Delaunay triangulation to find the edge points and continue as above. It does so by first sorting the points lexicographically (first by x-coordinate, and in case of a tie, by y-coordinate), and then constructing upper and lower hulls of the points in () time.. An upper hull is the part of the convex hull, which is visible from the above. Key words. This parameter forces the convex decomposition computation to be done using the mesh rescaled to fit a sphere with radius = Internal Scale. To make all this work in Unity you need random points in x-z-space and they should be stored as a Vertex in a list (Create a new Vertex object with a Vector3 as its position and where y = 0). In this case you take a V hull, keep the chines and keel where they are, but make the normally straight bottom panels concave. Save. The other implementation are quite complicated and will take a lot of time to convert so I'm looking for a C# version which is already working. In Unity, mesh to mesh collisions only work if at least one of the meshes is convex. So I switched back to using the convex hull. Use Unity to build high-quality 3D and 2D games, deploy them across mobile, desktop, VR/AR, consoles or the Web, and connect with loyal and enthusiastic players and customers. You can find them here: Convex hull algorithms. Collision detection algorithms for something you know is convex is much faster than concave… Step 2 is to loop through all other points to identify which points are on the convex hull. Then, algorithm in 2D (you should adapt to 3D) can be close to alpha shape algorithm, by Edelbrunner. Thank you for helping us improve the quality of Unity Documentation. Example Project that comes with Unity 5. Create a set of points using the endpoints of each line. In kinda sorta quasi-pseudocode. The α-concave hull on a set of points in the plane is a non-convex hull with angular constraints under the minimum area condition. Thanks in advance, If your concave corners are not too sharp, I might try doing a 3d Delaunay triangulation on the point set. I have heard that this can work well, but it is tricky to get right. 11 $\begingroup$ I have a list of discrete points wich I want to use as nodes for creating a 2D mesh. Unite all dots under the smallest possible area. Let the left convex hull be a and the right convex hull be b. This is how the algorithm works. In some cases yes. 3. First find the plane in which the polygon lies, doing a least squares fit of a small sample of the points is probably good enough. C#; Scripting API. Here is an example using Python. Check out my 3000 subs Special Video: https://youtu.be/Xm84wdUOE4MThanks for watching! Ask Question Asked 5 years, 2 months ago. Our concave collider component enables complex mesh to mesh collisions. I guess it was a bit poorly worded, I'll edit it now. Any pointers would be great. To recap: the idea of the area trigger concept is that it exists of a height and a 2d polygon, that can be concave. With Unity5 I have to flag the collider as "Convex" in order to select "Is Trigger"... the problem is that now I get an error: Cooking::cookConvexMesh: user-provided hull must have less than 256 vertices! Also, rasterization of the points into 2d and then preforming a edge find is pretty costly. In Unity 2017.3 and later you can mark the convex mesh to be inflated from the “Cooking Options” dropdown making sure “Inflate Convex Mesh” is enabled. to alpha shape algorithm, by Edelbrunner. The result depends on the user defined distance threshold. Following your suggestion, I did the following: Obtained the (lat, lon) hull values using from shapely.geometry import LineString and then, with the boundary values in hand, I projected them to the Earths surface using Pyproj and finally estimated the area using from shapely.geometry import shape.I can provide a code snippet if any of you want it. Also did you mean 3D k-sided polyhedron instead of polygon? We are here going to use the Gift wrapping algorithm, also known as a Jarvis March. ...and follow me on Twitter: @eriknordeus. And I do mean polygon, because I am looking for a 2-D shape projected into 3-D, https://stackoverflow.com/questions/3444001/simplified-concave-hulls/3453790#3453790, https://stackoverflow.com/questions/3444001/simplified-concave-hulls/3445440#3445440, It seems that the 2D case you linked to is more of the sparse point variety. Here I am using the exact same technique as used before, and here is what it looks like: Language English. 4. In my case, for a simple 9 sided concave polygon, there may be around 40000 points. Show all projects by intrepion. To find the convex hull of a set of points is a well-known problem studied in detail and there are many existing algorithms. What if you have several random points and want to find the smallest shape that's enclosing these points. Hi all, I've been working on a project that needs detailed raycasting collisions for ballistics hit calculations. The coordinate where a ray intersects with a plane, algorithm to figure out if a point is to the left, to the right, or on the same line as 2 other points. If I used the same algorithm, it seems that it would be wildly inefficient, https://stackoverflow.com/questions/3444001/simplified-concave-hulls/16412653#16412653. and it doesn't work anymore. Loop to generate the convex hull Vertex currentPoint = convexHull[0]; //Store colinear points here - better to create this list once than each loop List

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