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SIGGRAPH 2008 Presented by Ting-sheng Lin Taesoo Kwon 1   1 Seoul National University Kang Hoon Lee 2   2 Kwangoon Univers...
<ul><li>Introduction </li></ul><ul><li>Background </li></ul><ul><li>Graph Construction </li></ul><ul><li>Editing Group Mot...
 
<ul><li>Crowd Scenes </li></ul><ul><ul><li>Feature animation films </li></ul></ul><ul><ul><li>Video game </li></ul></ul><u...
<ul><li>Interactive editing scheme </li></ul><ul><ul><li>Complements  such simulation-based techniques </li></ul></ul><ul>...
<ul><li>Novel graph structure </li></ul><ul><ul><li>Each vertex : location of an individual at a sampled frame </li></ul><...
 
<ul><li>Synthesizing realistic group </li></ul><ul><ul><li>Agent models  [Reynolds 1987; Musse and Thalmann 1997; Pelechan...
<ul><li>Motion editing </li></ul><ul><ul><li>Motion clips to be manipulated with constraints  [Gleicher 1997; Lee and Shin...
<ul><li>Our approach </li></ul><ul><ul><li>Data-preserving shape editing  [Igarashi et al. 2005] </li></ul></ul><ul><ul><l...
 
<ul><li>Large crowd animation </li></ul><ul><ul><li>Tractable  motion clips </li></ul></ul><ul><ul><li>Each group motion c...
<ul><li>. </li></ul><ul><li>Formation edge </li></ul><ul><ul><li>Represent the neighborhood relationships between individu...
 
<ul><li>It is invariant on the uniform scaling of local features </li></ul><ul><ul><li>Unnaturally  enlarged ,  shrunken <...
<ul><li>Two-step optimization scheme  [Igarashi et al. 2005] </li></ul><ul><ul><li>Step one: scale-free construction </li>...
<ul><li>We consider three types of triangular features </li></ul><ul><ul><li>Spatial ,  temporal ,  spatiotemporal  featur...
<ul><ul><li>Spatial feature  </li></ul></ul>temporal feature spatiotemporal feature
<ul><li>Only the spatial features are scaled </li></ul><ul><li>Construct a spare linear system that can solve  E 1  and  E...
 
<ul><li>G and G’ having the  same number  of individuals N </li></ul><ul><li>Stitching two graphs requires three steps </l...
<ul><li>Second step </li></ul><ul><li>Final step: smoothly morphing group formations </li></ul><ul><ul><li>Linear blending...
 
<ul><li>Deformation or stitching of a group motion </li></ul><ul><ul><li>Collision ,  insufficient clearance </li></ul></u...
<ul><li>This speed change is often irregular </li></ul><ul><ul><li>Irregular speed change is usually undesirable in motion...
 
1. Battle field scene 2. Downtown scene
 
<ul><li>Conclusions  </li></ul><ul><ul><li>Animators to manipulate existing group motion data interactively </li></ul></ul...
Group Motion Editing
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Group Motion Editing

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SIGGRAPH 08

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Transcript of "Group Motion Editing"

  1. 1. SIGGRAPH 2008 Presented by Ting-sheng Lin Taesoo Kwon 1 1 Seoul National University Kang Hoon Lee 2 2 Kwangoon University Jehee Lee 3 3 Seoul National University Shigeo Takahashi 4 4 University of Tokyo
  2. 2. <ul><li>Introduction </li></ul><ul><li>Background </li></ul><ul><li>Graph Construction </li></ul><ul><li>Editing Group Motions </li></ul><ul><li>Stitching Group Motions </li></ul><ul><li>Postprocess </li></ul><ul><li>Experimental Results </li></ul><ul><li>Discussion </li></ul>
  3. 4.
  4. 5. <ul><li>Crowd Scenes </li></ul><ul><ul><li>Feature animation films </li></ul></ul><ul><ul><li>Video game </li></ul></ul><ul><li>State of the art </li></ul><ul><ul><li>Simulating each individual that chooses its action </li></ul></ul><ul><ul><li>Rules, decision models, force fields </li></ul></ul><ul><ul><li>Careful parameter tuning </li></ul></ul><ul><ul><li>Lack precise control of individuals </li></ul></ul><ul><ul><li>Laborious trial and error </li></ul></ul>
  5. 6. <ul><li>Interactive editing scheme </li></ul><ul><ul><li>Complements such simulation-based techniques </li></ul></ul><ul><ul><li>Animators have direct control over animated crowd behaviors </li></ul></ul><ul><ul><li>Selectively edit and combine some portions of the simulation results to achieve globally satisfactory results </li></ul></ul><ul><li>Manipulating the motion of multiple characters </li></ul><ul><ul><li>Repositioning only a few characters </li></ul></ul><ul><ul><li>Preserve each individual trajectory and group formation of individuals </li></ul></ul>
  6. 7. <ul><li>Novel graph structure </li></ul><ul><ul><li>Each vertex : location of an individual at a sampled frame </li></ul></ul><ul><ul><li>Connecting edge : individual moving trajectories and neighborhood formation </li></ul></ul><ul><li>Mesh editing method [Igarashi et al. 2005] </li></ul><ul><ul><li>Deform a group motion </li></ul></ul><ul><ul><li>Stitch two independent group motions </li></ul></ul><ul><ul><li>Avoiding collisions </li></ul></ul>
  7. 9. <ul><li>Synthesizing realistic group </li></ul><ul><ul><li>Agent models [Reynolds 1987; Musse and Thalmann 1997; Pelechano et al. 2005, Shao and Terzopoulos 2005] </li></ul></ul><ul><ul><li>Directly model [Chenney 2004, Hughes 2003; Treuille et al. 2006] </li></ul></ul><ul><ul><li>Data-driven method of constructing group behavior models [Lai et al. 2005; Lee et al. 2007; Lerner et al. 2007; Courth and Corpetti 2007; Paris et al. 2007] </li></ul></ul>
  8. 10. <ul><li>Motion editing </li></ul><ul><ul><li>Motion clips to be manipulated with constraints [Gleicher 1997; Lee and Shin 1999] </li></ul></ul><ul><ul><li>Concatenated [Rose et al. 1996] </li></ul></ul><ul><ul><li>Interpolated [Rose et al. 1998; Mukai and Kuriyama 2005] </li></ul></ul><ul><ul><li>Rearranged [Lee et al. 2002; Kovar et al. 2002; Arikan et al. 2003] </li></ul></ul><ul><li>Our goal is to provide users with a similar level of flexibility in edition group motions </li></ul>
  9. 11. <ul><li>Our approach </li></ul><ul><ul><li>Data-preserving shape editing [Igarashi et al. 2005] </li></ul></ul><ul><ul><li>Maintaining the local arrangement of vertices allows user to intuitively manipulate 2D and 3D shapes </li></ul></ul><ul><ul><li>As-Rigid-As-Possible Shape Manipulation [Igarashi et al. SIGGARPH 05] </li></ul></ul>
  10. 13. <ul><li>Large crowd animation </li></ul><ul><ul><li>Tractable motion clips </li></ul></ul><ul><ul><li>Each group motion clip consists of a set two-dimensional moving trajectories of individual characters </li></ul></ul><ul><ul><li>Preserving spatial relations among individuals </li></ul></ul>
  11. 14. <ul><li>. </li></ul><ul><li>Formation edge </li></ul><ul><ul><li>Represent the neighborhood relationships between individuals </li></ul></ul><ul><ul><li>Challenge: correctly identify the formational relationships </li></ul></ul><ul><ul><ul><li>Neighborhoods can vary according to time </li></ul></ul></ul><ul><ul><ul><li>Don’t keep pace with other characters and moves at variable speeds </li></ul></ul></ul><ul><ul><li>Delaunay triangulation of vertices at each plane </li></ul></ul><ul><li>Motion edge </li></ul><ul><ul><li>Connect with the vertex of the corresponding character at the previous plane and next plane </li></ul></ul>
  12. 16.
  13. 17. <ul><li>It is invariant on the uniform scaling of local features </li></ul><ul><ul><li>Unnaturally enlarged , shrunken </li></ul></ul>G G’
  14. 18. <ul><li>Two-step optimization scheme [Igarashi et al. 2005] </li></ul><ul><ul><li>Step one: scale-free construction </li></ul></ul><ul><ul><li>Step two: scale adjustment </li></ul></ul><ul><ul><li>Graph undergoes a large deformation </li></ul></ul><ul><ul><ul><li>Highly-distorted </li></ul></ul></ul><ul><ul><ul><li>Near-degenerate triangles </li></ul></ul></ul><ul><li>Group motion editing </li></ul><ul><ul><li>Motion artifacts: sudden velocity changes </li></ul></ul><ul><ul><li>Spatial group formation: scale-adjustment </li></ul></ul><ul><ul><li>Temporal distortion: time-warping </li></ul></ul>
  15. 19. <ul><li>We consider three types of triangular features </li></ul><ul><ul><li>Spatial , temporal , spatiotemporal features </li></ul></ul>V t V t+1 V t-1 w t s t u t V t V t+1 V t-1 w t s t u t V t V t+1 V t-1 w t s t u t
  16. 20. <ul><ul><li>Spatial feature </li></ul></ul>temporal feature spatiotemporal feature
  17. 21. <ul><li>Only the spatial features are scaled </li></ul><ul><li>Construct a spare linear system that can solve E 1 and E 2 </li></ul><ul><ul><li>Variable elimination [Igarashi et al. 2005] </li></ul></ul><ul><ul><li>Lagrange multiplier scheme </li></ul></ul>
  18. 23. <ul><li>G and G’ having the same number of individuals N </li></ul><ul><li>Stitching two graphs requires three steps </li></ul><ul><li>First step </li></ul>Bipartite graph matching algorithm [Belongie et al. 2002] G G’ G G’
  19. 24. <ul><li>Second step </li></ul><ul><li>Final step: smoothly morphing group formations </li></ul><ul><ul><li>Linear blending don’t generate desired results </li></ul></ul><ul><ul><li>We blend triangular (spatial, temporal, spatiotemporal) </li></ul></ul>Aligned two motion clips by translating and rotating them to best match the boundary [Kovar et al. 2002] G’’ G G’
  20. 26. <ul><li>Deformation or stitching of a group motion </li></ul><ul><ul><li>Collision , insufficient clearance </li></ul></ul><ul><ul><li>Collision avoidance algorithm: approximate and iterative method </li></ul></ul><ul><ul><li>Certain threshold : two trajectories </li></ul></ul><ul><ul><li>Pulls the trajectories away by 10% of the threshold and repeats this process until all collision are resolved </li></ul></ul><ul><li>Avoid collision with obstacles </li></ul><ul><ul><li>We pull the deepest penetrating point toward the nearest point on the boundary of the obstacle </li></ul></ul>
  21. 27. <ul><li>This speed change is often irregular </li></ul><ul><ul><li>Irregular speed change is usually undesirable in motion editing </li></ul></ul><ul><ul><li>Time warping </li></ul></ul>
  22. 29. 1. Battle field scene 2. Downtown scene
  23. 31. <ul><li>Conclusions </li></ul><ul><ul><li>Animators to manipulate existing group motion data interactively </li></ul></ul><ul><ul><li>Detail-preserving approach </li></ul></ul><ul><ul><li>Advantage: direct, precise control </li></ul></ul><ul><li>Limitations </li></ul><ul><ul><li>Cannot large deformation, but lead to unnatural speedup/slowdown </li></ul></ul><ul><ul><li>Cannot handle a large crowd consisting of thousands character </li></ul></ul><ul><li>Future work </li></ul><ul><ul><li>Deal with a wider variety of group behaviors (e.g: chatting, Olympic …) </li></ul></ul>
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