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I am working a bit with spatial data, and am running a lot through Blender because ArcGIS can't handle it as well. I've come across an issue that I can't seem to figure out, it affects a few files, but this is the simplest one.

The shape was made by extruding a polygon between two tins in ArcGIS, creating a Multipatch feature. This was exported from ArcGIS as a WRL file. The volume in ArcGIS was calculated as 144.878252 m3, which given the rough dimensions (10 m x 6m x 2.4m) is correct accounting for variation of the non-smooth top surface.

When the WRL is imported into Blender, the calculated volume (using the 3D printing add-on) gives a value of 176.16027832 m3.

The reason why I need to calculate volumes in Blender is that is there are more complex shapes that ArcGIS will not calculate the volume for.

I am running Blender 2.77. Any help would be appreciated.

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After downloading your file this is what I found ...

  1. Your model surface normals are flipped randomly.
  2. The flipped normal caused the add-on to give an incorrect readout.
  3. To solve the issue go to Shading/Uvs tab on your 3dview Tool Panel here

enter image description here

  1. Click on the Recalculate button in the Normals section.
  2. Now your Normals are rearranged so they are facing the right side up.
  3. Do the add-on volume calculation will give you the correct result.

REMOVE OPEN EDGES...
1. Go into edit mode press Tab
2. Make sure to select all your model's faces.
3. Hit W and select remove double.
4. Remove double command here :

enter image description here

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  • $\begingroup$ Thanks for this, I completely forgot about normals. I gave that a go and the volume calculation changed to 71.052 m3, still a bit smaller than what it should be. Any further ideas? $\endgroup$ – JoshDragon Apr 23 '18 at 5:33
  • $\begingroup$ Mine is showing 144877716.0645cm3, probably you still have some normals not facing the right way? Check to make sure you don't have any open edges too. Do the remove double command in blender. $\endgroup$ – hawkenfox Apr 23 '18 at 5:58
  • $\begingroup$ I removed the duplicates and that worked. Thanks so much for the help! $\endgroup$ – JoshDragon Apr 23 '18 at 7:49

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