<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>Dan, Siqi,</div><div> the patch should be committed. I remember the original discussion, we never followed up</div><div>committing the patch. It's time to do it.</div><div>However, since the fast marching method is probably used by a lot of people, how about</div><div>adding a cmake flag to revert to the "wrong" implementation to ensure backward compatibility?</div><div><br></div><div><br></div><div>Luca</div><div><br></div><br><div><div>On Jan 7, 2010, at 10:42 PM, siqi chen wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><br>I think the patch correctly implements the FMM method described by Sethian. <br><br>Thanks<br>Siqi<br><br><br><div class="gmail_quote">On Thu, Jan 7, 2010 at 1:54 PM, Dan Mueller <span dir="ltr"><<a href="mailto:dan.muel@gmail.com">dan.muel@gmail.com</a>></span> wrote:<br> <blockquote class="gmail_quote" style="border-left-width: 1px; border-left-style: solid; border-left-color: rgb(204, 204, 204); margin-top: 0pt; margin-right: 0pt; margin-bottom: 0pt; margin-left: 0.8ex; padding-left: 1ex; position: static; z-index: auto; ">Hi Siqi,<br> <br> I managed to find some time to take a look at the issue you reported.<br> <br> I think the following patch will help:<br> <a href="http://public.kitware.com/Bug/view.php?id=8990" target="_blank">http://public.kitware.com/Bug/view.php?id=8990</a><br> <br> Here is the results I get with the patch applied:<br> <br> The distance from [50,50] to [49.7,49.8] is: 0.36<br> The distance from [49,49] to [49.7,49.8] is: 1.06<br> The distance from [49,50] to [49.7,49.8] is: 0.73<br> The distance from [50,49] to [49.7,49.8] is: 0.85<br> The distance from [48,49] to [49.7,49.8] is: 2.06<br> The distance from [48,50] to [49.7,49.8] is: 1.73<br> The distance from [49,48] to [49.7,49.8] is: 2.06<br> The distance from [49,51] to [49.7,49.8] is: 1.73<br> The distance from [50,48] to [49.7,49.8] is: 1.85<br> The distance from [50,51] to [49.7,49.8] is: 1.36<br> The distance from [51,49] to [49.7,49.8] is: 1.85<br> The distance from [51,50] to [49.7,49.8] is: 1.36<br> <br> Is that what you expected?<br> <br> Hope this helps.<br> <br> Cheers, Dan<br> <br> 2010/1/5 siqi chen <<a href="mailto:siqichensc@gmail.com">siqichensc@gmail.com</a>>:<br> <div><div></div><div class="h5">><br> > I read a few more papers and thought about the question number 2 again. I<br> > think there is misinterpretation on my part. The 4 neighbors of [49.7,49.8]<br> > along their exact distance value should be set as Alive Points instead of<br> > Trial Points. Then the neighbors of the 4 neighbors (another layer around<br> > the 4 neighbors) are set as trial points, their initial tentative values are<br> > calculated using upwind difference method. When I check the result distance<br> > map, a few things to notice:<br> > 1. The distance value of the 4 neighbors of [49.7, 49.8] are correct. This<br> > is obvious since I set them as Known instead of Trial.<br> > 2. The distance value of the neighbors of the 4 neighbors (the input trial<br> > points) still changed. I think this is due to the inherent FMM accuracy and<br> > update method.<br> ><br> > You can try this with the following code.<br> > <a href="http://www.rpi.edu/%7Echens/download/main3.cpp" target="_blank">http://www.rpi.edu/~chens/download/main3.cpp</a><br> ><br> > Thanks<br> > Siqi<br> ><br> > On Mon, Jan 4, 2010 at 6:03 PM, siqi chen <<a href="mailto:siqichensc@gmail.com">siqichensc@gmail.com</a>> wrote:<br> >><br> >> To better illustrate my questions regarding fast marching, I put 2 example<br> >> code in the attachment.<br> >><br> >> In main1.cpp, I simply compute a distance map to point [50,50]. As you can<br> >> see from the output, the distances from the 4 neighbors of [50,50] to<br> >> [50,50] are correct, obviously the result is 1. However, the distance from<br> >> [51,51] to [50,50] is 1.707 instead of 1.414, which is obviously wrong. I<br> >> think this is due to the fast marching accuracy itself. If we switch to<br> >> higher order FMM, the result should be improved.<br> >><br> >> In main2.cpp, I perturb the target point a little bit. Instead, I want to<br> >> compute the distance map to point [49.7,49.8]. From my point of<br> >> understanding, I need to initialize the 4 neighbors of [49.7, 49.8] and put<br> >> them into the TrialPoints. As you can see, I compute the exact distance from<br> >> these 4 neighbors to [49.7,49.8] and put them into TrialPoints. However,<br> >> when I go back and check the result distance map, some thing is different.<br> >> The distances from these 4 neighbors to [49.7,49.8] are changed. As you can<br> >> see, the distance from [50,50] to [49.7,49.8] remains correct. This is<br> >> because this value is the smallest in the TrialPoints, therefore it is<br> >> pushed in to the AlivePoints heap first and the value is frozen since then.<br> >> I think there is something wrong here about whether to update trial points<br> >> value or not. If this trial point is user specified, then the value should<br> >> not be updated. I noticed a related discussion a couple of months ago in the<br> >> mailing list,<br> >> <a href="http://www.itk.org/pipermail/insight-users/2009-May/030282.html" target="_blank">http://www.itk.org/pipermail/insight-users/2009-May/030282.html</a><br> >><br> >> <a href="http://www.rpi.edu/%7Echens/download/main1.cpp" target="_blank">http://www.rpi.edu/~chens/download/main1.cpp</a><br> >> <a href="http://www.rpi.edu/%7Echens/download/main2.cpp" target="_blank">http://www.rpi.edu/~chens/download/main2.cpp</a><br> >><br> >> Any input is appreciated.<br> >> Siqi<br> >><br> >><br> >> On Mon, Jan 4, 2010 at 3:32 PM, Dan Mueller <<a href="mailto:dan.muel@gmail.com">dan.muel@gmail.com</a>> wrote:<br> >>><br> >>> Hi Siqi,<br> >>><br> >>> Indeed I am familiar with Fast Marching. I saw your question to the<br> >>> mailing list, but did not respond because I have not experienced what<br> >>> you describe: when I set the trial point value, that is the value in<br> >>> the arrival function.<br> >>><br> >>> Perhaps you could post to the mailing list a minimal example<br> >>> (code+cmake+data) demonstrating your issue. That would make it really<br> >>> easy for me to help you!<br> >>><br> >>> Cheers, Dan<br> >>><br> >>> 2010/1/4 siqi chen <<a href="mailto:siqichensc@gmail.com">siqichensc@gmail.com</a>>:<br> >>> > Hi, Dan,<br> >>> ><br> >>> > Sorry to bother you. From the ITK mailing list, I noticed you reported<br> >>> > a bug<br> >>> > about FastMarchingImageFilter couple of months ago. So I guess you are<br> >>> > a<br> >>> > fast marching expert : )<br> >>> ><br> >>> > I am trying to use FastMarchingImageFilter to calculate a distance map<br> >>> > to a<br> >>> > set of points which have non-integer coordinates and I want the result<br> >>> > to be<br> >>> > as accurate as possible. Here is what I did, but the result is not very<br> >>> > accurate.<br> >>> ><br> >>> > First I find the integer points which are the neighbors of the target<br> >>> > points<br> >>> > and set these integer points as trial points. Then I use some<br> >>> > interpolation<br> >>> > method to initialize the distance from these trial points to the target<br> >>> > points, which are assumed to be "exactly correct". The TrialPoints in<br> >>> > the<br> >>> > FastMarchingImageFilter is defined as this set of trial points and<br> >>> > their<br> >>> > corresponding distances to the target points. The AlivePoints is empty.<br> >>> > When<br> >>> > I check the result distance map, I find that the distance value of<br> >>> > these<br> >>> > trial points are changed, they are no longer what their initial states<br> >>> > are.<br> >>> > Therefore, the iso curve deviate the original input a little bit. I am<br> >>> > quite<br> >>> > confusing about this result.<br> >>> ><br> >>> > I noticed you mentioned on the mailing list about neighbor update, that<br> >>> > is<br> >>> > to distinguish between user-specified trial points and<br> >>> > algorithm-generated<br> >>> > trial points. here is the discussion,<br> >>> > <a href="http://www.itk.org/pipermail/insight-users/2009-May/030282.html" target="_blank">http://www.itk.org/pipermail/insight-users/2009-May/030282.html</a> . I<br> >>> > wonder<br> >>> > if you have any suggestions about my problem.<br> >>> ><br> >>> > Any input is appreciated.<br> >>> ><br> >>> > Thanks<br> >>> > Siqi Chen<br> >>> ><br> >><br> ><br> ><br> </div></div>> _____________________________________<br> > Powered by <a href="http://www.kitware.com" target="_blank">www.kitware.com</a><br> ><br> > Visit other Kitware open-source projects at<br> > <a href="http://www.kitware.com/opensource/opensource.html" target="_blank">http://www.kitware.com/opensource/opensource.html</a><br> ><br> > Kitware offers ITK Training Courses, for more information visit:<br> > <a href="http://www.kitware.com/products/protraining.html" target="_blank">http://www.kitware.com/products/protraining.html</a><br> ><br> > Please keep messages on-topic and check the ITK FAQ at:<br> > <a href="http://www.itk.org/Wiki/ITK_FAQ" target="_blank">http://www.itk.org/Wiki/ITK_FAQ</a><br> ><br> > Follow this link to subscribe/unsubscribe:<br> > <a href="http://www.itk.org/mailman/listinfo/insight-users" target="_blank">http://www.itk.org/mailman/listinfo/insight-users</a><br> ><br> ><br> </blockquote></div><br> _____________________________________<br>Powered by <a href="http://www.kitware.com">www.kitware.com</a><br><br>Visit other Kitware open-source projects at<br><a href="http://www.kitware.com/opensource/opensource.html">http://www.kitware.com/opensource/opensource.html</a><br><br>Kitware offers ITK Training Courses, for more information visit:<br>http://www.kitware.com/products/protraining.html<br><br>Please keep messages on-topic and check the ITK FAQ at:<br>http://www.itk.org/Wiki/ITK_FAQ<br><br>Follow this link to subscribe/unsubscribe:<br>http://www.itk.org/mailman/listinfo/insight-users<br></blockquote></div><br></body></html>