GiD forum

Thanks all for the tips about normals and volumes.

I already use the normals, and have menu entries to visualize the
orientation of surfaces with arrows and colors ... and use the
information “SAME1ST DIFF1ST” provided by GiD in an external
C++ routine ...
I was just looking for some way to automatise some tasks (and so
not risk any errors).

I know the sign of a scalar product can provide the reciprocal
“orientation” between two vectors or surface normals.
But I was asking if the surface points inside or outside a VOLUME,
not its orientation relative to another one.
What I don't know is if in GiD there are some already build in
functions to avoid the use of computational geometry routines and
calculation of area around spherical angles
to detect if a free point
in space is inside or outside a volume (not easily the convex hull
defined from some of his points).
And since GiD is a solid modeller I was thinking of some of the
routines used in Boolean operation with volumes, or something
similar. May be in a future version it could be an information
provided, I don’t know

The information “SAME1ST DIFF1ST” doesn’t offer me what I was
looking for because it tells me only if the orientation of a surface is
consistent with an initial reciprocal orientation between the normal
of surface 1 and the z axis.
At the end so is still a “human” choice to say if a normal to a surface
is pointing inside or outside a volume.
Sorry for the long mail.
Thanks in any case.




Andrea Calaon

Ashurst Lodge, Ashurst
Southampton, Hampshire
SO40 7AA, UK
Tel. office: +44 23 80 293 223
Fax office: +44 23 80 292 853
Mobile: +44 7766 488 225
E-mail: andrea at beasy.com
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In GiD, If a volume has a surface as boundary, with Orientation == SAME1ST, then
the surface normal points inside the volume, else the normal points outside.

Enrique Escolano

----- Original Message -----
From: Andrea Calaon
To: gidlist at gatxan.cimne.upc.es
Sent: Wednesday, April 09, 2003 5:02 PM
Subject: [GiDlist] Product and tools


Thanks all for the tips about normals and volumes.




I already use the normals, and have menu entries to visualize the orientation of surfaces with arrows and colors ... and use the information "SAME1ST DIFF1ST" provided by GiD in an external C++ routine ...

I was just looking for some way to automatise some tasks (and so not risk any errors).




I know the sign of a scalar product can provide the reciprocal "orientation" between two vectors or surface normals.

But I was asking if the surface points inside or outside a VOLUME, not its orientation relative to another one.

What I don't know is if in GiD there are some already build in functions to avoid the use of computational geometry routines and calculation of area around spherical angles . to detect if a free point in space is inside or outside a volume (not easily the convex hull defined from some of his points).

And since GiD is a solid modeller I was thinking of some of the routines used in Boolean operation with volumes, or something similar. May be in a future version it could be an information provided, I don't know .

The information "SAME1ST DIFF1ST" doesn't offer me what I was looking for because it tells me only if the orientation of a surface is consistent with an initial reciprocal orientation between the normal of surface 1 and the z axis.

At the end so is still a "human" choice to say if a normal to a surface is pointing inside or outside a volume.

Sorry for the long mail.

Thanks in any case.










Andrea Calaon


Ashurst Lodge, Ashurst
Southampton, Hampshire
SO40 7AA, UK
Tel. office: +44 23 80 293 223
Fax office: +44 23 80 292 853
Mobile: +44 7766 488 225
E-mail: andrea at beasy.com
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