Profile

Isaak Lim, M.Sc.
Room 109
Phone: +49 241 8021805
Fax: +49 241 8022899
Email: isaak.lim@cs.rwth-aachen.de


Presentations

Event
Type
Title
SGP 2016   Paper   Identifying Style of 3D Shapes using Deep Metric Learning


Publications


Anne Gehre, Isaak Lim, Leif Kobbelt
Computer Graphics Forum (Proc. EUROGRAPHICS 2016)

Feature curves on surface meshes are usually defined solely based on local shape properties such as dihedral angles and principal curvatures. From the application perspective, however, the meaningfulness of a network of feature curves also depends on a global scale parameter that takes the distance between feature curves into account, i.e., on a coarse scale, nearby feature curves should be merged or suppressed if the surface region between them is not representable at the given scale/resolution. In this paper, we propose a computational approach to the intuitive notion of scale conforming feature curve networks where the density of feature curves on the surface adapts to a global scale parameter. We present a constrained global optimization algorithm that computes scale conforming feature curve networks by eliminating curve segments that represent surface features, which are not compatible to the prescribed scale. To demonstrate the usefulness of our approach we apply isotropic and anisotropic remeshing schemes that take our feature curve networks as input. For a number of example meshes, we thus generate high quality shape approximations at various levels of detail.

» Show BibTeX
@inproceedings{gehre2016adapting, title={Adapting Feature Curve Networks to a Prescribed Scale}, author={Gehre, Anne and Lim, Isaak and Kobbelt, Leif}, booktitle={Computer Graphics Forum}, volume={35}, number={2}, pages={319--330}, year={2016}, organization={Wiley Online Library} }





Isaak Lim, Anne Gehre, Leif Kobbelt
Eurographics Symposium on Geometry Processing 2016

We present a method that expands on previous work in learning human perceived style similarity across objects with different structures and functionalities. Unlike previous approaches that tackle this problem with the help of hand-crafted geometric descriptors, we make use of recent advances in metric learning with neural networks (deep metric learning). This allows us to train the similarity metric on a shape collection directly, since any low- or high-level features needed to discriminate between different styles are identified by the neural network automatically. Furthermore, we avoid the issue of finding and comparing sub-elements of the shapes. We represent the shapes as rendered images and show how image tuples can be selected, generated and used efficiently for deep metric learning. We also tackle the problem of training our neural networks on relatively small datasets and show that we achieve style classification accuracy competitive with the state of the art. Finally, to reduce annotation effort we propose a method to incorporate heterogeneous data sources by adding annotated photos found online in order to expand or supplant parts of our training data.

» Show BibTeX
@article{Lim:2016:StyleLearning, author = "Lim, Isaak and Gehre, Anne and Kobbelt, Leif", title = "Identifying Style of 3D Shapes using Deep Metric Learning", journal = "Computer Graphics Forum", volume = 35, number = 5, year = 2016 }





Michael Kremer, David Bommes, Isaak Lim, Leif Kobbelt
22nd International Meshing Roundtable, Orlando, Florida, USA.

A purely topological approach for the generation of hexahedral meshes from quadrilateral surface meshes of genus zero has been proposed by M. Müller-Hannemann: in a first stage, the input surface mesh is reduced to a single hexahedron by successively eliminating loops from the dual graph of the quad mesh; in the second stage, the hexahedral mesh is constructed by extruding a layer of hexahedra for each dual loop from the first stage in reverse elimination order. In this paper, we introduce several techniques to extend the scope of target shapes of the approach and significantly improve the quality of the generated hexahedral meshes. While the original method can only handle "almost convex" objects and requires mesh surgery and remeshing in case of concave geometry, we propose a method to overcome this issue by introducing the notion of concave dual loops. Furthermore, we analyze and improve the heuristic to determine the elimination order for the dual loops such that the inordinate introduction of interior singular edges, i.e. edges of degree other than four in the hexahedral mesh, can be avoided in many cases.




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