From: Pablo d'A. <pab...@we...> - 2006-12-18 21:43:37
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Hi all, The latest talk about robust estimation made me realize that I wanted to try if using an M-estimator during optimization has a beneficial effect, especially when used straight with control points from autopano. I have added support for the Huber M-estimator. Excerpt from doc/Optimise.txt: # # 'm'-line options # ---------------- # # m0 use Huber m-estimator during second optimisation pass. # This will reduce the weight of control points with higher # errors. It might help a little if a pano contains a few # inaccurate or completely wrong control points. # 0: no m-estimator (as in previous versions) # Any other number is the sigma parameter of the huber # m-estimator. Control points with errors higher than sigma # will have less influence during the optimisation. # A good value for sigma might be 2. I haven't evaluated it yet, since I need to stitch two large panos to compare if things have improved. Its hard to tell from the preview in hugin ;-) |
From: Daniel M. G. <dm...@uv...> - 2006-12-19 20:50:24
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Hi Pablo, Do you know where I can read about it? BTW, I checked the paper you mentioned in Max's forum (the one comparing different types of cameras). I wonder if the main issue was not ridigity, but lack of estimation of the sensor shift. dmg Pablo d'Angelo twisted the bytes to say: Pablo> Hi all, Pablo> The latest talk about robust estimation made me realize that I wanted to try Pablo> if using an M-estimator during optimization has a beneficial effect, Pablo> especially when used straight with control points from autopano. Pablo> I have added support for the Huber M-estimator. Excerpt from doc/Optimise.txt: Pablo> # Pablo> # 'm'-line options Pablo> # ---------------- Pablo> # Pablo> # m0 use Huber m-estimator during second optimisation pass. Pablo> # This will reduce the weight of control points with higher Pablo> # errors. It might help a little if a pano contains a few Pablo> # inaccurate or completely wrong control points. Pablo> # 0: no m-estimator (as in previous versions) Pablo> # Any other number is the sigma parameter of the huber Pablo> # m-estimator. Control points with errors higher than sigma Pablo> # will have less influence during the optimisation. Pablo> # A good value for sigma might be 2. Pablo> I haven't evaluated it yet, since I need to stitch two large panos to Pablo> compare if things have improved. Its hard to tell from the preview in hugin ;-) Pablo> ------------------------------------------------------------------------- Pablo> Take Surveys. Earn Cash. Influence the Future of IT Pablo> Join SourceForge.net's Techsay panel and you'll get the chance to share your Pablo> opinions on IT & business topics through brief surveys - and earn cash Pablo> http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV Pablo> _______________________________________________ Pablo> PanoTools-devel mailing list Pablo> Pan...@li... Pablo> https://lists.sourceforge.net/lists/listinfo/panotools-devel -- Daniel M. German "For indeed who is there alive that will not be swayed by his bias and partiality to Jonathan Swift -> the place of his birth?" http://turingmachine.org/ http://silvernegative.com/ dmg (at) uvic (dot) ca replace (at) with @ and (dot) with . |
From: Pablo d'A. <pab...@we...> - 2006-12-19 23:51:09
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Daniel M. German schrieb: > Hi Pablo, > > Do you know where I can read about it? I don't have the definite reference, but I was reading Matthew Browns excellent "Automatic Panoramic Image Stitching using Invariant Features" and he seems to use it as well. http://www.cs.ubc.ca/~mbrown/research/research.html The definite reference seems to be Robust Statistics, Peter. J. Huber, Wiley, 1981 but I haven't read that yet. > BTW, I checked the paper you mentioned in Max's forum (the one > comparing different types of cameras). I wonder if the main issue was > not ridigity, but lack of estimation of the sensor shift. They do estimate the principal point (d,e in panotools speak), and with 3D targets, the estimation is better conditioned. I don't remember the results exactly, it was something like the calibration accuracy of the same lens was less on the 300D than on other body. (Not that it would concern us, they are looking at photogrammetric applications, and have higher requirements than we do). Also the influence of the orientation on some zoom lenses was quite interesting. ciao Pablo |