You are dealing with two problems here: determining the faces that define the
surface of your points and generating triangles and normals for those faces.
The Triangulator utility helps with the second problem but not the first.
If the points are completely "unstructured" (that is, if you have no information
about where the faces are), then one way of generating a surface is to calculate
the convex hull of the points. This is the set of surfaces which enclose the
points as if they were "gift wrapped". There are several algorithms which can
produce the convex hull-- you may be able to find an implementation out there
somewhere.
Doug Gehringer
Sun Microsystems
> From: <[EMAIL PROTECTED]>
> Subject: Re: [JAVA3D] Creating a cube with GeometryInfo
>
> Although I haven't tried your example, I'm pretty sure, that it deals with
> a plane (all z-coordinates are 0). As Dennis J. Bouvier pointed out
> already, this is considerably easier then my case of a closed volume.
> However, I still think that a class called Triangulator should be able to
> deal with this. It seems a very common task compared to the generation of
> planes with possible holes.
> The problem is, given a set of points in 3D and no information about
> conncetions between them, how do I generate triangles. I'm no expert in
> this area (obviously) but wouldn't Delaunay triangulation do nicely? Is
> there any code available doing this (inside or outside Java3D)?
>
> Regards
>
> HEIKO
> [EMAIL PROTECTED]
>
>
>
>
> Daniel Selman <[EMAIL PROTECTED]>@java.sun.com> on 20-10-99 17:24:30
>
> Please respond to [EMAIL PROTECTED]
>
> Sent by: Discussion list for Java 3D API <[EMAIL PROTECTED]>
>
>
> To: [EMAIL PROTECTED]
> cc:
>
> Subject: Re: [JAVA3D] Creating a cube with GeometryInfo
>
>
> Your Name (sic!),
>
> Here is an example (from my book) that works.
>
> Sincerely,
>
> Daniel Selman
>
> [EMAIL PROTECTED]
> http://www.tornadolabs.com
>
> ======
>
> //generate a surface from 10 vertices and create a hole in the surface by
> removing
> //a hole defined using 5 vertices. Note that the hole must be entirely
> within the
> //outer polygon.
> private double[] m_VertexArray = {1,1,0, //0
> 0,3,0, //1
> 1,5,0, //2
> 2,4,0, //3
> 4,5,0, //4
> 3,3,0, //5
> 4,2,0, //6
> 4,0,0, //7
> 3,0,0, //8
> 2,1,0, //9
> //these are vertices for the hole
> 1,3,0, //10
> 2,3,0, //11
> 3,2,0, //12
> 3,1,0, //13
> 2,2,0};//14
> //triangulate the polygon
> GeometryInfo gi = new GeometryInfo( GeometryInfo.POLYGON_ARRAY );
>
> gi.setCoordinates( m_VertexArray );
>
> //the first 10 points make up the outer edge of the polygon, the next five
> make up the hole
> int[] stripCountArray = {10,5};
> int[] countourCountArray = {stripCountArray.length}
> gi.setContourCounts( countourCountArray );
> gi.setStripCounts( stripCountArray );
>
> Triangulator triangulator = new Triangulator();
> triangulator.triangulate( gi );
>
> //also generate normal vectors so that the surface can be light
> NormalGenerator normalGenerator = new NormalGenerator();
> normalGenerator.generateNormals( gi );
>
> //create an appearance
> Appearance ap = new Appearance();
>
> //render as a wireframe
> PolygonAttributes polyAttrbutes = new PolygonAttributes();
> polyAttrbutes.setPolygonMode( PolygonAttributes.POLYGON_LINE );
> polyAttrbutes.setCullFace( PolygonAttributes.CULL_NONE ) ;
> ap.setPolygonAttributes( polyAttrbutes );
>
> //add both a wireframe and a solid version of the triangulated surface
> Shape3D shape1 = new Shape3D( gi.getGeometryArray(), ap );
> Shape3D shape2 = new Shape3D( gi.getGeometryArray() );
>
> -----Original Message-----
> From: Discussion list for Java 3D API
> [mailto:[EMAIL PROTECTED]]On Behalf Of Your Name
> Sent: 20 October 1999 04:14
> To: [EMAIL PROTECTED]
> Subject: [JAVA3D] Creating a cube with GeometryInfo
>
>
> Hi,
>
> I'm sure there is an easy answer to this, but I still can't get it to work.
> What I'm trying to do is to display a simple cube within Java3D. Now, I
> know, I could use the ColorCube class for this (works fine), but I want to
> do it via the GeometryInfo to be able to later on create more complicated
> objects. So what I do is to define the 8 vertices of a cube to be
> (0,0,0),(0,0,1),... up to (1,1,1), pass this set of coordinates to the
> GeometryInfo, triangulate, generate normals, stripify and create a Shape3D
> from it. Code is as follows:
>
> GeometryInfo gInfo=new GeometryInfo(GeometryInfo.POLYGON_ARRAY);
> gInfo.setCoordinates(mCoords);
> int[] ii={mCoords.length/3};
> gInfo.setStripCounts( ii);
> Triangulator tri=new Triangulator();
> tri.triangulate(gInfo);
> NormalGenerator normGen=new NormalGenerator();
> normGen.generateNormals(gInfo);
> Stripifier strip=new Stripifier();
> strip.stripify(gInfo);
> Shape3D shape=new Shape3D();
> shape.setGeometry(gInfo.getGeometryArray());
>
> However, when I display the Shape3D, I get a bunch of triangles and not the
> total cube. Now I first thought that some of the faces where backface
> culled, so I set the PolgonAttributes correspondingly:
>
> Appearance app=new Appearance();
> PolygonAttributes pAtt=new PolygonAttributes();
> pAtt.setCullFace(PolygonAttributes.CULL_NONE);
> pAtt.setBackFaceNormalFlip(true);
> app.setPolygonAttributes(pAtt);
> Material mat=new Material();
> mat.setAmbientColor(0.4f,0.4f,0.4f);
> app.setMaterial(mat);
> shape.setAppearance(app)
> Still, the same effect, only a few triangles show up, not a full cube.
>
> Probably I did misunderstand the way the Triangulator works, can anybody
> shed light on this?
>
> Regards
>
> HEIKO
> [EMAIL PROTECTED]
>
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