Volume calculation negative, SR10


#1

I’m having some trouble with the volume calculation returning negative for a brep that appears to be solid. There are no naked edges, and the IsSolid() returns true. Yet I’m getting a negative volume back. Running Version 5 SR10 64-bit
(5.10.41001.13395, 10/1/2014)

neg-vol.3dm (223.9 KB)


(Pascal Golay) #2

I see that, thanks.
Shrinking the underlyng surfaces (ShrinkTrimmedSrf on the brep before asking for Volume) will help in the short term, I’ll ask the developer to have a look at why this is happening.

http://mcneel.myjetbrains.com/youtrack/issue/RH-28947

-Pascal


#3

Hi,
Using Rhino V5 SR14 32bit, I am also getting a negative volume from a closed mesh object. The report from the check command tells me it is a good mesh (see below). The above “neg-vol.3dm” file provided by pickedgator also gives me a negative “Volume = -2618.04332 (+/- 3.1e+06) cubic millimeters”. Please help.
Thank you

This is a good mesh.

General information about this mesh:
Mesh does not have any degenerate faces.
Mesh does not have any extremely short edges.
Mesh does not have any non manifold edges.
Mesh does not have any naked edges.
Mesh does not have any duplicate faces.
Mesh does not have any faces with directions different from the mesh as a whole.
Mesh does not have any self intersecting faces.
Mesh does not have any disjoint pieces.
Mesh has 1 unused vertex.

ID: 7eb9a244-87d7-4c5e-8084-c3b288cf68fe (24)
Layer name: Default
Render Material:
source = from layer
index = -1
Groups:
Mesh[02_5cm
-
Cloud]
Group03
8)
Geometry:
Valid mesh.
Closed polygon mesh: 33166 vertices, 65870 polygons with normals
bounding box: (3.56886,3.27622,0.315109) to (5.39983,6.13502,7.3109)
Geometry UserData:
UserData ID: 3B7FB506-437C-431e-B1D7-93C4CBFF417F
Plug-in: Rhino
description: Gumball grip frame
saved in file: yes
copy count: 7


(John Brock) #4

See if the Dir command shows the white arrows pointing inside.
If it does, use the Flip command line option in Dir and see if that sorts it.
If not, please send us the file and reference this message thread:

Thanks


#5

Hi John
By flipping the directions using the “Dir” command, it gives me the same number, but a positive volume.
I am good now. Thanks
George


(John Brock) #6

That makes sense.
Closed meshes can be “inside out”, where Rhino does not let closed polysurfaces be inverted like that.

If you have a display mode setup so “backface settings” are set to a funny color or to be culled, then you can quickly see if a mesh needs to have it’s normals to be flipped.