# 3D points to 3D model

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Hi, Does any one know how to create a nice 3D model out of random 3D points? How is it possible to find the points needed to create the outer surface and find which points have to be connected? Thank you in advance. Greetings, Michael

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Do you want a concave boundary object? It won't use all of the points but look into a 3D convex hull algorithm. You might be able to use that as a starting point to create a 3D object that uses all of the points.

How random are these points? Do you have an example of why you need this? Might be easier to find a solution then.

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I'm aware of two methods:

1. Compute the Delaunay tetrahedralization of the point cloud. Then use a floodfill over the graph of tetrahedra starting with an initial "seed" point that you know is inside (or outside) to classify all the tetrahedra as either "solid" or "air." Then throw out all the faces of the tetrahedra except those that are shared by both "solid" and "air" tetrahedra. Those faces that remain are a nice triangle mesh for your point cloud.

2. There's an algorithm (or, a class of algorithms) called the "ball-pivoting" method; you can google this.

And actually, I suppose there's a third (which is probably not to be recommended, but I'll put it here in case; it might be useful say if you have noisy data and you want a method which rather than using your original points as vertices instead computes a smoother surface which is "close" to them.):

3. Associate to each point an "influence function" (e.g., inverse square law, or poly6 kernel); add up (or otherwise combine (e.g., by taking the max, or the harmonic mean)) these influence functions to get a scalar density function, and then compute an isosurface of this using the marching cubes or marching tetrahedra algorithm.

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I've seen people using MeshLab for tasks such as these.

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Quote:
 Original post by AIRMichael2Does any one know how to create a nice 3D model out of random 3D points? Greetings, Michael

For a 3d model you need verticies(points) and indicies (indexes of verticies that a triangle corner refers to). Idicies allow you to have a surface over theese points. I have no idea of how to compute indicies info out of verticies, you have very many passible results. You need a triangle list with 3 indexes per triangle

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The problem has been solved with a easy solution: I have connected all points to each other with a triangle. This solution seems to be also quite fast for rendering. Thanks everyone!

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