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TetraMaker[pts_, surface_, TetGenString_?StringQ] := 
Module[{inInst, outInst, coords, surface1, meshElements, facets}, 
        inInst = TetGenCreate[];
        TetGenSetPoints[inInst, pts];
        facets = Partition[surface, 1];
        TetGenSetFacets[inInst, facets];
        outInst = TetGenTetrahedralize[inInst, TetGenString];
        coords = TetGenGetPoints[outInst]; (* element point *)
        surface1 = TetGenGetFaces[outInst]; (* element face *)
        meshElements = TetGenGetElements[outInst]; (* element indices *)
      {coords, surface1, meshElements}];

 TetrahedraVolume = 
         Compile[{{coords, _Real, 2}, {elements, _Integer, 1}}, 
         Block[{p}, p = coords[[elements]];
             1/6*Abs[Det[p[[{1, 2, 3}]] - p[[{2, 3, 4}]]]]], 
              RuntimeAttributes -> {Listable}, RuntimeOptions -> "Speed"];

 {coords1, surface1, meshElements1} = TetraMaker[data01, polysurface1, "pqa.8"];
  vb = Total[TetrahedraVolume[coords1, meshElements1]]
  Graphics3D[GraphicsComplex[coords1, Polygon[surface1]]]

Error dialog appears when running code below:

 {coords2, surface2, meshElements2} = TetraMaker[data02, polysurface2, "pqa.8"];
  vb = Total[TetrahedraVolume[coords2, meshElements2]]

Assertion failed!

Program: ... File: M:\Builds\2615350\checkout\Mathematica...\tetgen.cxx Line: 21962

Expression: dir !=COLLOSIONFACE

For information on how your program can cause an assertion failure, see the Visual C++ documentation on asserts

(Press Retry to debug the application - JIT must be enabled)

I am trying to calculate volume. I wonder if both data sets are similar then why does it not work for 2nd data set? Is there any way I can fix this error?

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1 Answer 1

up vote 9 down vote accepted

Your second data set has intersecting facets. There is no way TetGen can tetrahedralize that.

res = TetGenDetectIntersectingFacets[data02, 
   Partition[polysurface2, 1]];
Graphics3D[GraphicsComplex[res[[1]], Polygon[res[[2]]]]]

enter image description here

So the solution is to fix the data set. I have to see about how to improve the assertion error. The problem is that there are duplicate faces. If you use

sf2 = DeleteDuplicates[Sort /@ polysurface2];
{coords1, surface1, meshElements1} = 
  TetraMaker[data02, sf2, "pqa.8"];
vb = Total[TetrahedraVolume[coords1, meshElements1]]
Graphics3D[GraphicsComplex[coords1, Polygon[surface1]]]

it will work.

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@ ruebenko: very helpful, any hint on how to fix the data set. –  mathew Jul 5 '12 at 3:37
@Jay, this update should do it. I am curious, could you comment on what type of data this is and what the application is? –  user21 Jul 5 '12 at 16:24
@Jay, interesting. Is this lab data? How do you get the surface facets of the particles? –  user21 Jul 5 '12 at 17:02
@Jay, thanks for the clarification. Concerning the contour selection, one would need to see an example to say how this could be done in Mathematica. –  user21 Jul 5 '12 at 18:36
@Jay, I think it were good if you were to post this part as a new question. Many more people will then look at this. –  user21 Jul 5 '12 at 19:02

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