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John Brosz & Faramarz Samavati University of Calgary Shape Modeling International – June 2010 1

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Outline 1. Scenario/Motivation 2. Goals 3. Related Work 4. Observations 5. Projection Surface Formulation 6. Rendering 7. Applications 2

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Figure from Transformations & Projection in Computer Graphics, Salomon, Springer, 2006 4

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5 i = R Figure from Transformations & Projection in Computer Graphics, Salomon, Springer, 2006

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6 z j = + ( i, j ) = ( R,, + ) Figure from Transformations & Projection in Computer Graphics, Salomon, Springer, 2006

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Spherical Projection Equation 9 ( i, j ) =

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Goals Create panoramas that: 1. Allow for exploration & customization 2. Are defined by modeling 3. Build on existing intuition 4. Allow for visual understanding Single Viewpoint: no “slit cameras”. 15

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Related Work Panoramas from Perspective Images Image from http://www.cirq.de/mosaicing.html Image from Szeliski & Shum, Creating full view panoramic image mosaics and environment maps, Siggraph 1997 16

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Related Work Correcting Distortion Images from Carrol, Agrawala & Agarwala, Optimizing Content-Preserving Projections for Wide-Angled Images, Siggraph 2009 17

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Related Work Single-Center Projections Images from Trapp & Döllner, Generalization of Single-Center Projections Using Projection Tile Screens, VISIGRAPP, 2008 Normal Map Panorama 18

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Common Panoramas 20

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Observations 1. Shapes are associated with panoramas 21

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Observations 1. Shapes are associated with panoramas 2. Angular change 22

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Observations 1. Shapes are associated with panoramas 2. Angular Change 3. Parameterization is important 23 ( i, j ) = ( R,, + ) ( i, j ) =

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Shape Defined Panoramas Defined by two curves 1. Outline: closed, controls horizontal sampling 24

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Shape Defined Panoramas Defined by two curves 1. Outline: closed, controls horizontal sampling 25

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Shape Defined Panoramas Defined by two curves 1. Outline: closed, controls horizontal sampling 2. Profile: open, controls vertical sampling 26

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Shape Defined Panoramas Defined by two curves 1. Outline: closed, controls horizontal sampling 2. Profile: Open, controls vertical sampling Curves parameterized by arc-length 27

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Shape Defined Panoramas Mix between surface of revolution and surface extrusion Profile Outline Extrusion Surface 28

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Shape Defined Panoramas Mix between surface of revolution and surface extrusion Profile Outline Panorama Surface 29

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Example 1 Profile Outline 30

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Example 2 31 Outline

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Example 2 Before After 32

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Shape Defined Panoramas Multiple Profiles 33

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Shape Defined Panoramas Multiple Profiles 34

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Rendering Ray-tracing Image Re-sampling Nonlinear Projection on GPU 36

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Rendering Ray-tracing x x 37

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Rendering Image Re-sampling 38

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Rendering Nonlinear Projection on GPU 1. Find projection equation 2. Project vertices with equation on GPU 3. Be careful with seams 39

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Find Projection Equation World Coordinates Normalized Device Coordinates 40

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Find Projection Equation Only surfaces that map onto spherical coordinates. Projection Surface: Q(u,v) = (x,y,z) Projection Volume: t (0,0,0) + (1-t) Q(u,v) 1. Find spherical coordinates of p = (x,y,z) 2. Search for u,v s.t. Q(u,v) with same spherical coords. 3. t = || p || || Q(u,v) || 41

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Find Projection Equation Search for u,v s.t. Q(u,v) with same spherical coords. 42

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Project Vertices with GPU Override projection matrix with nonlinear projection equation. This only moves vertices! Triangles are filled as if linearly projected. Nonlinearly Projected Triangle Triangle w/ Linear Fill Algorithm 43

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Seams 44

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Seams 45

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Rendering Performance Single pass algorithm 60 fps with 100K polygons on NVIDIA 8800 GTS 46

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Application: Custom Panorama 47

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Application: Re-projecting Panoramas 48

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Application: Animated Projection 49

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Application: Interactive Local Editing 50

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Application: Interactive Local Editing 51

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Conclusions Use of modeling to define a projection. Use of Arc-length to dictate parameterization. Visual means for creating panoramas. Realtime GPU based rendering of panoramas. 52

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THANK-YOU 53

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