Problem with FindNormalFast at a TGeoScaledShape

Hi,

I believe FindNormalFast is not giving the correct normal at the surface of my TGeoScaledShape.

I'm stepping through my geometry (half a sphere plus an ellipsoid plus a cone segment, all shells) with FindNextBoundaryAndStep and then asking for the normal from FindNormalFast.

Here is an example of a situation where there seems to be a problem:

http://www.nikhef.nl/~cjreed/pmtReflectExample.png

The track is the red line. The normal is shown by the blue line, and does not seem to actually be normal to the surface.

The result is that the "reflection" winds up sending the photon out of the volume!

The macro to reproduce this situation can be found at:

http://www.nikhef.nl/~cjreed/testGeoTracker.C

I have tried both Root v5.24.00 and v5.26.00b on Linux-x86_64 and gotten the same results.

Thanks for your help!

• Corey

PS - FindNextBoundaryAndStep seems to be going to the outer edge of the shell rather than the inner. Should I have expected this? Why don't I get two boundary points, one at the inner surface of the shell and one at the outer surface? Received on Mon Mar 22 2010 - 18:27:06 CET