METU
Department of Computer Engineering
Spring 2015
CENG 789—Digital Geometry Processing
ASSIGNMENT III
Instructor: Y. Sahillioğlu
May X, 2015
2 Weeks
Rigid Shape Registration (start early!)
Mesh Deformation {100 points} Your task is to bring all 10 partial scans of the same object into
one common pose. By doing so, you will be compensating the deficiencies of the individual scans, e.g.,
invisible right ear of the bunny at the 4th pose from the top is compensated by the 5th pose once they
are aligned, or equivalently, registered.
The good news is that these scans differ only by rigid transformations, i.e., rotations and translations,
which are easy to compute, as described in the class. The bad news is, not that bad actually, you first
need to uniformly subsample each scan to work with less number of points. You will then register the first
scan to the second, and then register this temporary result to the third scan, and so on, which in turn
accumulates the missing data as you process towards the last scan. For the registration, you first decide
the corresponding points between two point clouds by a simple closest-point matching algorithm (use
kd-trees for efficiency) and then compute the rigid transformation that aligns the corresponding points
well (easy, as mentioned). You then recompute the closest-point correspondences and repeat, until your
new transformation does not differ much from the previous transformation, i.e., until mesh stops moving.
Submission This is 15% of your final grade. Use the meshes provided in ∼ys/meshes3.zip. Good luck.
Send to ys@ceng.metu.edu.tr your code, executable, and resulting file(s) as well as mynotes.txt file where
you mention the encountered problems and interesting observations.