Northridge, Los Angeles – September 26, 2015 Graph Drawing Pixel & Voxel Representations of Graphs Md. Jawaherul Alam Tiomas Bläsius Ignaz Rutuer Torsuen Ueckerdt Alexander Wolff
. Motivation Build contact representation of graphs Pixel & Voxel Representations Md. Jawaherul Alam GD 2015
. Motivation Build contact representation of graphs Pixel & Voxel Representations Md. Jawaherul Alam GD 2015
. Motivation Build contact representation of graphs Pixel & Voxel Representations Md. Jawaherul Alam GD 2015
. Motivation Build contact representation of graphs Pixel & Voxel Representations Md. Jawaherul Alam GD 2015
. Contact Representations Md. Jawaherul Alam Pixel & Voxel Representations Goal: minimize polygonal complexity GD 2015 9 9 8 6 5 8 7 7 4 6 2 5 1 9 4 3 2 3 1 8 2 7 3 5 9 9 4 6 1 8 8 4 5 7 7 6 6 6 5 5 3 4 7 4 1 2 3 3 2 8 2 1 1 9 ■ Vertices ⇒ Geometric objects (polygons, arcs, polyhedra) ■ Edges ⇒ Contacts
. Contact Representations Md. Jawaherul Alam Pixel & Voxel Representations Goal: minimize polygonal complexity GD 2015 9 9 8 6 5 8 7 7 4 6 2 5 1 9 4 3 2 3 1 8 2 7 3 5 9 9 4 6 1 8 8 4 5 7 7 6 6 6 5 5 3 4 7 4 1 2 3 3 2 8 2 1 1 9 ■ Vertices ⇒ Geometric objects (polygons, arcs, polyhedra) ■ Edges ⇒ Contacts
. Motivation Build contact representation of graphs Pixel & Voxel Representations Md. Jawaherul Alam GD 2015
. Motivation Build contact representation of graphs from unit blocks How many unit blocks are required? Pixel & Voxel Representations Md. Jawaherul Alam GD 2015
. Motivation Build contact representation of graphs from unit blocks How many unit blocks are required? Pixel & Voxel Representations Md. Jawaherul Alam GD 2015
. Pixel and Voxel Representations Pixel in 2D, Voxel in 3D Pixel & Voxel Representations Md. Jawaherul Alam GD 2015 ■ Building contact representation from unit blocks
. Pixel and Voxel Representations Pixel & Voxel Representations Md. Jawaherul Alam GD 2015 ■ Building contact representation from unit blocks ■ Pixel in 2D, Voxel in 3D
. Pixel and Voxel Representations Md. Jawaherul Alam Pixel & Voxel Representations Goal: minimize total number of pixels/voxels GD 2015 1 1 5 3 2 4 3 5 5 4 4 2 3 1 2 ■ Vertices ⇒ Blobs (connected sets of pixels/voxels) ■ Edges ⇒ Adjacent (face-to-face) pixels/voxels in two blobs
. Pixel and Voxel Representations Md. Jawaherul Alam Pixel & Voxel Representations Goal: minimize total number of pixels/voxels GD 2015 1 1 5 3 2 4 3 5 5 4 4 2 3 1 2 ■ Vertices ⇒ Blobs (connected sets of pixels/voxels) ■ Edges ⇒ Adjacent (face-to-face) pixels/voxels in two blobs
. Pixel Representations Md. Jawaherul Alam Pixel & Voxel Representations Goal: minimize total number of pixels GD 2015 1 1 5 2 4 3 5 4 2 3 ■ Vertices ⇒ Blobs (connected sets of pixels) ■ Edges ⇒ Adjacent (face-to-face) pixels in two blobs
. Pixel Representations Md. Jawaherul Alam Pixel & Voxel Representations Goal: minimize total number of pixels GD 2015 1 1 1 5 3 5 2 4 3 4 5 4 2 3 2 ■ Vertices ⇒ Blobs (connected sets of pixels) ■ Edges ⇒ Adjacent (face-to-face) pixels in two blobs
. Pixel Representations Md. Jawaherul Alam Pixel & Voxel Representations Goal: minimize total number of pixels GD 2015 1 1 1 5 3 5 2 4 3 4 5 4 2 3 2 ■ Vertices ⇒ Blobs (connected sets of pixels) ■ Edges ⇒ Adjacent (face-to-face) pixels in two blobs
. Pixel Representations Md. Jawaherul Alam Pixel & Voxel Representations Goal: minimize total number of pixels GD 2015 1 1 1 5 3 5 33 23 2 4 3 4 5 4 2 3 2 ■ Vertices ⇒ Blobs (connected sets of pixels) ■ Edges ⇒ Adjacent (face-to-face) pixels in two blobs
. Pixel Representations Md. Jawaherul Alam Pixel & Voxel Representations Goal: minimize total number of pixels GD 2015 1 1 1 1 5 5 3 12 3 5 33 23 4 2 4 3 4 5 2 4 2 3 2 ■ Vertices ⇒ Blobs (connected sets of pixels) ■ Edges ⇒ Adjacent (face-to-face) pixels in two blobs
. Pixel Representations Md. Jawaherul Alam Pixel & Voxel Representations Goal: minimize total number of pixels GD 2015 1 1 1 1 5 5 3 12 3 5 33 23 4 2 4 3 4 5 2 4 2 3 2 ■ Vertices ⇒ Blobs (connected sets of pixels) ■ Edges ⇒ Adjacent (face-to-face) pixels in two blobs
. Voxel Representations Md. Jawaherul Alam Pixel & Voxel Representations Goal: minimize total number of voxels GD 2015 1 46 3 8 4 5 3 1 5 5 4 4 2 2 3 1 2 ■ Vertices ⇒ Blobs (connected sets of voxel) ■ Edges ⇒ Adjacent (face-to-face) voxels in two blobs
. Voxel Representations Md. Jawaherul Alam Pixel & Voxel Representations Goal: minimize total number of voxels GD 2015 1 46 3 8 4 5 3 1 5 5 4 4 2 2 3 1 2 ■ Vertices ⇒ Blobs (connected sets of voxel) ■ Edges ⇒ Adjacent (face-to-face) voxels in two blobs
. Related Work Contact Representations Point-contact with circles [Koebe, 1936] Point-contact with triangles [De Fraysseix et al., 1994] Side-contact with hexagons [Gansner et al., 2010], [Bonichon et al., 2010] Pixel & Voxel Representations Md. Jawaherul Alam GD 2015
. Related Work Contact Representations [Gansner et al., 2010], [Bonichon et al., 2010] Pixel & Voxel Representations Md. Jawaherul Alam GD 2015 ■ Point-contact with circles [Koebe, 1936] ■ Point-contact with triangles [De Fraysseix et al., 1994] ■ Side-contact with hexagons
. Related Work Contact Representations with Rectilinear Polygons [Yeap and Sarrafzadeh, 1993], [He, 1999], [Liao et al., 2003] Pixel & Voxel Representations Md. Jawaherul Alam GD 2015 ■ Contact with 8-sided rectilinear polygons:
. Contact Representation of nonplanar graphs Md. Jawaherul Alam Pixel & Voxel Representations Related Work GD 2015 [Felsner and Francis, 2011] [Thomassen, 1986], [Bremner et al., 2012] Contact Representations in 3D ■ Contact representation of planar graphs with cuboids ■ Improper contact representation of planar graphs with cubes 2 3 4 1 5 6 7 8 9
. [Felsner and Francis, 2011] Md. Jawaherul Alam Pixel & Voxel Representations Related Work GD 2015 Contact Representations in 3D [Thomassen, 1986], [Bremner et al., 2012] ■ Contact representation of planar graphs with cuboids ■ Improper contact representation of planar graphs with cubes ■ Contact Representation of nonplanar graphs 2 3 4 1 5 6 7 8 9
. Related Work Vertex Contact Graphs of Paths on a Grid (VCPG) Mosaic Drawing Contact of square or hexagonal tilies [Cano et al., 2015] Same representation, different objective! Pixel & Voxel Representations Md. Jawaherul Alam GD 2015 ■ Contact graphs of grid paths [Aerts and Felsner, 2014]
. Related Work Vertex Contact Graphs of Paths on a Grid (VCPG) Mosaic Drawing Same representation, different objective! Pixel & Voxel Representations Md. Jawaherul Alam GD 2015 ■ Contact graphs of grid paths [Aerts and Felsner, 2014] ■ Contact of square or hexagonal tilies [Cano et al., 2015]
. Related Work Vertex Contact Graphs of Paths on a Grid (VCPG) Mosaic Drawing Same representation, different objective! Pixel & Voxel Representations Md. Jawaherul Alam GD 2015 ■ Contact graphs of grid paths [Aerts and Felsner, 2014] ■ Contact of square or hexagonal tilies [Cano et al., 2015]
. Min-Pixel-Representation Md. Jawaherul Alam Pixel & Voxel Representations Our Result Min-Voxel-Representation GD 2015 Find a grid drawing with unit edge lengths Input: a planar max-degree-4 graph Reduction from: NP-complete in both 2D and 3D Computational Complexity ■ Finding minimum-size representation is 1 5 2 4 3 1 2 3 4 5 6 7 1 2 3 4 5 6 7
. Min-Pixel-Representation Md. Jawaherul Alam Pixel & Voxel Representations Our Result Min-Voxel-Representation GD 2015 Find a grid drawing with unit edge lengths Computational Complexity NP-complete in both 2D and 3D ■ Finding minimum-size representation is 1 5 Reduction from: P 2 4 3 Input: a planar max-degree-4 graph G P ⇓ 1 2 3 4 ⇓ 5 6 7 1 2 3 4 5 6 7
. , Md. Jawaherul Alam Pixel & Voxel Representations Our Result voxels are sufficient , For a graph with genus voxels are necessary and sufficient GD 2015 For a graph with treewidth voxels are sufficient Voxel Representation Computational Complexity Pixel Representation NP-complete in both 2D and 3D ■ Finding minimum-size representation is 1 5 2 3 4 ■ For a k -outerplanar graph, Θ( kn ) pixels are necessary and sufficient 1 2 3 4 5 6 7 1 2 3 4 5 6 7
. , Md. Jawaherul Alam Pixel & Voxel Representations Our Result voxels are sufficient , For a graph with genus voxels are necessary and sufficient GD 2015 For a graph with treewidth Voxel Representation Computational Complexity Pixel Representation NP-complete in both 2D and 3D ■ Finding minimum-size representation is 1 5 2 3 4 ■ For a k -outerplanar graph, Θ( kn ) pixels are necessary and sufficient ■ O ( n 2 ) voxels are sufficient 1 2 3 4 5 6 7 1 2 3 4 5 6 7
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