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 Post subject: Generating a concave mesh from a point cloudPosted: Tue Jan 04, 2011 12:35 pm

Joined: Tue Jan 26, 2010 1:49 pm
Posts: 7
Hi,
I am using the Kinect sensor to generate a point cloud of a section of the surrounding room.
I need to generate from the point cloud the corresponding set of collision surfaces in Bullet.
I have tried using the btConvexHullShape to load the point cloud. This works but creates a convex mesh from the points,
which is a nonsense shape, as the point cloud really describes a concave shape.

What is the best/easiest way to generate a concave mesh from the point cloud?

It looks like I can add triangles to a btTriangleMesh and use that to generate a btBvhTriangleMeshShape, but I don't have the triangle data, just the points.
I could try and run a marching-cubes-style algorithm to manually generate the triangle information, but I'm wondering if this kind of utility function may exist already within Bullet?
Essentially the same kind of functionality as provided for convex objects by the btConvexHullShape.

Does anyone have a code snippet, or tips on how to do this?

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 Post subject: Re: Generating a concave mesh from a point cloudPosted: Tue Jan 04, 2011 6:55 pm

Joined: Thu Nov 26, 2009 6:32 pm
Posts: 76
You need a surface reconstructing software. You can try Meshlab.

http://lcni.uoregon.edu/~mark/Projects/ ... inspection

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 Post subject: Re: Generating a concave mesh from a point cloudPosted: Wed Jan 05, 2011 8:13 am

Joined: Tue Mar 02, 2010 6:13 am
Posts: 66
there are many many algorithms to generate a convex hull from a point cloud,
take a look at qhull , etc ...
or this : http://www.bulletphysics.org/Bullet/php ... f=12&t=255

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 Post subject: Re: Generating a concave mesh from a point cloudPosted: Wed Jan 05, 2011 1:09 pm

Joined: Mon Jan 03, 2011 4:26 pm
Posts: 43
majestik666 wrote:
there are many many algorithms to generate a convex hull from a point cloud,
take a look at qhull , etc ...
or this : http://www.bulletphysics.org/Bullet/php ... f=12&t=255

The point cloud represents an entire scene, though, diamond is trying to generate a general mesh, not a convex one. A convex mesh would lose all the detail he's trying to get.

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 Post subject: Re: Generating a concave mesh from a point cloudPosted: Wed Jan 05, 2011 3:50 pm

Joined: Fri May 30, 2008 2:51 am
Posts: 508
Location: Ossining, New York
maybe you want some sort of voronoi-like thing, with a threshold for maximum distance between two points

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