[Insight-developers] Tolerance on Rigid2DTransform
Miller, James V (Research)
millerjv at crd.ge.com
Tue, 23 Mar 2004 08:57:20 -0500
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Julien,
The CVS log for Rigid2DTransform says that you adjusted the tolerance for
the test for orthogonality because a transform written with MetaIO was
loosing too much precision on write (or read) operation that it was no
longer orthogonal when re-imported.
Instead of changing the orthogonality test, can you change the MetaIO to
write the transform with greater precision? The best option would be to
write the transform out in binary (no loss of precision). If the format
needs to be ASCII, you can write a greater number of decimal places
(something extreme like 12 or 20).
I have been burnt in the past in a shape inspection project by a transform
loosing precision when written to disk. I was trying to measure deviations
to under 0.001 inches. The loss in precision which caused the transforms to
no longer be orthogonal meant that portions of my geometry were being warped
(non-rigidly) to be outside my tolerances. Eventually, I tracked down the
problem to the calibration system storing the transforms in ASCII (single
precision). Due to the legacy of the application, I couldn't make the switch
to a binary format for the transform. But increasing the number of decimal
places in the ASCII formats gave the application just enough precision room
to perform properly.
Jim Miller
_____________________________________
Visualization & Computer Vision
GE Research
Bldg. KW, Room C218B
P.O. Box 8, Schenectady NY 12301
millerjv at research.ge.com <mailto:millerjv at research.ge.com>
james.miller at research.ge.com
(518) 387-4005, Dial Comm: 8*833-4005,
Cell: (518) 505-7065, Fax: (518) 387-6981
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<DIV><SPAN class=497254013-23032004><FONT size=2>Julien,</FONT></SPAN></DIV>
<DIV><SPAN class=497254013-23032004><FONT size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=497254013-23032004><FONT size=2>The CVS log for
Rigid2DTransform says that you adjusted the tolerance for the test for
orthogonality because a transform written with MetaIO was loosing too much
precision on write (or read) operation that it was no longer orthogonal when
re-imported.</FONT></SPAN></DIV>
<DIV><SPAN class=497254013-23032004><FONT size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=497254013-23032004><FONT size=2>Instead of changing the
orthogonality test, can you change the MetaIO to write the transform with
greater precision? The best option would be to write the transform out in
binary (no loss of precision). If the format needs to be ASCII, you can
write a greater number of decimal places (something extreme like 12 or
20).</FONT></SPAN></DIV>
<DIV><SPAN class=497254013-23032004><FONT size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=497254013-23032004><FONT size=2>I have been burnt in the past
in a shape inspection project by a transform loosing precision when written to
disk. I was trying to measure deviations to under 0.001 inches. The
loss in precision which caused the transforms to no longer be orthogonal meant
that portions of my geometry were being warped (non-rigidly) to be outside my
tolerances. Eventually, I tracked down the problem to the calibration
system storing the transforms in ASCII (single precision). Due to the legacy of
the application, I couldn't make the switch to a binary format for the
transform. But increasing the number of decimal places in the ASCII
formats gave the application just enough precision room to perform properly.
</FONT></SPAN></DIV>
<DIV><SPAN class=497254013-23032004><FONT size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=497254013-23032004><FONT size=2></FONT></SPAN> </DIV>
<DIV>
<P style="MARGIN: 0in 0in 0pt"><B><SPAN
style="COLOR: navy; FONT-FAMILY: 'Comic Sans MS'">Jim Miller</SPAN></B>
<BR><B><I><SPAN
style="FONT-SIZE: 10pt; COLOR: red; FONT-FAMILY: Arial">_____________________________________</SPAN></I></B><BR><EM><SPAN
style="FONT-SIZE: 7.5pt; COLOR: black; FONT-FAMILY: Arial">Visualization &
Computer Vision</SPAN></EM><I><SPAN
style="FONT-SIZE: 7.5pt; COLOR: black; FONT-FAMILY: Arial"><BR><EM>GE
Research</EM><BR><EM>Bldg. KW, Room C218B</EM><BR><EM>P.O. Box 8, Schenectady NY
12301</EM><BR><BR></SPAN></I><EM><U><SPAN
style="FONT-SIZE: 7.5pt; COLOR: blue"><A
href="mailto:millerjv at research.ge.com">millerjv at research.ge.com</A></SPAN></U></EM></P>
<P style="MARGIN: 0in 0in 0pt"><EM><U><SPAN
style="FONT-SIZE: 7.5pt; COLOR: blue">james.miller at research.ge.com</SPAN></U></EM><BR><I><SPAN
style="FONT-SIZE: 7.5pt; COLOR: black; FONT-FAMILY: Arial">(518) 387-4005, Dial
Comm: 8*833-4005, </SPAN></I><BR><I><SPAN
style="FONT-SIZE: 7.5pt; COLOR: black; FONT-FAMILY: Arial">Cell: (518) 505-7065,
Fax: (518) 387-6981</SPAN></I> </P></DIV>
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