[vtkusers] duplicated vertex in marching cubes?

[lucas Grijander]

This is my code. Basically I have a mesh "geometry" and I project rays in order to fill the matrix of points. 
***********************************vtkStructuredPoints *object = prepareVTKObjectForMarching(geom,40);
//Iso-surface using marching cubesvtkMarchingCubes* iso = vtkMarchingCubes::New();iso->SetInput(object);iso->SetValue(0,1); // Surface #0, iso-value=1		iso->Update();
then the function prepareVTKObjectForMarching
vtkStructuredPoints* prepareVTKObjectForMarching(osg::Geometry *geometry, int steps, string name){	TBBox bbox = createBoundingBox(geometry);
	bbox.length[0] *= 1.2;	bbox.length[1] *= 1.2;	bbox.length[2] *= 1.2;
	float lengthStep = bbox.length[bbox.maxLAxis]/(float)steps;
	int dim[3];	dim[0] = steps;	dim[1] = steps;	dim[2] = steps;	double ar[3];	ar[0] = lengthStep;	ar[1] = lengthStep;	ar[2] = lengthStep;    double origin[3];	origin[0] = bbox.origin[0];	origin[1] = bbox.origin[1];	origin[2] = bbox.origin[2];
	vtkStructuredPoints *strcP = vtkStructuredPoints::New();
	// Set data dimensions, spacing and origin    strcP->SetDimensions(dim);     strcP->SetSpacing(ar);    strcP->SetOrigin(origin); 
    vtkDataSet *ds = strcP ;
    vtkDataSetAttributes *a = ds->GetPointData() ;
    // Data may be vtkUnsignedCharArray or vtkUnsignedShortArray    vtkUnsignedCharArray *scalars = vtkUnsignedCharArray::New();		unsigned int cnt = 0;

	float zInit = origin[2];
	for(int x = 0; x < steps; x++)	{		float xf = bbox.origin[0] + x*lengthStep;		
		for(int y = 0; y < steps; y++)		{			float yf = bbox.origin[1] + y*lengthStep;			
			vector<float> listT = getIntersectionPoints(xf,yf,zInit,geometry);
			if(listT.size() == 2)			{				float zIn = zInit + listT.at(0);				float zOut = zInit + listT.at(1);
				bool particleAdded = false;				for(int z = 0; z < steps; z++)				{					float zf = origin[2] + z*lengthStep;
					if(zf >= zIn && zf <= zOut)					{						scalars->InsertValue(cnt, 128) ;						particleAdded = true;					}					else if(zf < zIn)scalars->InsertValue(cnt, 0) ;					else if(zf > zOut && particleAdded == false)					{						scalars->InsertValue(cnt,128);						particleAdded = true;					}					else scalars->InsertValue(cnt, 0) ;					cnt++;				}				}				else if(listT.size() == 4)			{				float zIn1 = zInit + listT.at(0);				float zOut1 = zInit + listT.at(1);
				float zIn2 = zInit + listT.at(2);				float zOut2 = zInit + listT.at(3);
				for(int z = 0; z < steps; z++)				{					float zf = origin[2] + z*lengthStep;					if((z >= zIn1 && z <= zOut1) || (z >= zIn2 && z <= zOut2))					{						scalars->InsertValue(cnt, 128);					}					else scalars->InsertValue(cnt, 0) ;					cnt++;									}						}					else			{								for(int z = 0; z < steps; z++)				{					scalars->InsertValue(cnt, 0) ;					cnt++;				}			}		}	}
	a->SetScalars(scalars) ;
	return strcP;}


> Date: Wed, 11 Nov 2009 10:33:06 -0500
> Subject: Re: [vtkusers] duplicated vertex in marching cubes?
> From: bill.lorensen at gmail.com
> To: dev_crisalix at hotmail.com
> CC: vtkusers at vtk.org
> 
> Please provide a small, complete example. MC should not generate
> duplicate points or vertices. What is the datatype of your scalars?
> 
> On Wed, Nov 11, 2009 at 10:20 AM, lucas Grijander
> <dev_crisalix at hotmail.com> wrote:
> >
> > Hi all!
> > I am using vtkMarchingCubes to calculate a 3D mesh of a volume I have. Fist
> > I initialize the filter with:
> > vtkMarchingCubes* iso = vtkMarchingCubes::New();
> > iso->SetInput(object);
> > iso->SetValue(0,1); // Surface #0, iso-value=1
> > iso->Update();
> > then I fill the vtkStructuredPoints.
> > The problem I have is, as you can see in the pictures, when you have a close
> > look to the trianbles (screen2) you can see duplicated triangles and vertex,
> > and this is a huge problem for my application... I supposed vtkMarchingCubes
> > should generate a single surface mesh... I don't know if that's the reason,
> > but when I fill the vtkStructuredPoints I use
> > scalars->InsertValue(cnt, 0) ; and scalars->InsertValue(cnt, 128) ;
> > I took all these from an example, I still don't know what you have to set as
> > values, either 1 or 128... in addition the result change with this number
> > and I'm not sure why.
> > What should I use as values? and also why I have this "double" triangles
> > mesh?
> > thanks!
> > Jaime.
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