It means that the streakline thinks it has stepped into a tetra, but when it tries to find the exit point from the tetra, it can't. (If your data is cubes, it is decomposed into tetras under the covers). It considers each face in turn, and determines the cosine of the angle between the face normal and the vector. If the cosine is <= 0, then the vector diverges from the face, and it isn't considered further. If not, it scales the cosine by the distance between the point and the face to get the necessary step along the vector to reach the face in the vector direction, and then chooses the face requiring the smallest step. Problem is that all the cosines are negative (or zero), so the vector diverges from *all* the faces. Which means that there's a problem in the data, maybe a degenerate element or something. Or more likely, floating point error is just making it look that way.
Greg
Lloyd A
Treinish/Watson/[EMAIL PROTECTED] To:
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[EMAIL PROTECTED] Subject: [opendx-users]
problems with Streakline
son.ibm.com
05/30/2002 02:17 PM
Please respond to
opendx-users
I occasionally get the following error from Streakline:
"Internal error: can't find intersection".
Other time steps or starting points with the same vector series work ok.
With different data sets the problem may or may not appear. Before I start
looking at the code, does anyone know the origin or meaning of this error?
Thanks.
