Artistic Multiprojection Rendering

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Artistic Multiprojection Rendering

• Maneesh Agrawala Stanford University
• Denis Zorin New York University
• Tamara Munzner Stanford University

Eurographics Rendering Workshop 2000
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Motivation

• Artists often deviate from linear projection
• Alter projection for each object
• Curvilinear, nonlinear, inverted

• Express mood, feeling, idea

• Improve comprehensibility
• Visualize spatial relationships

Giorgio de Chiricos Mystery and Melancholy of a
Street
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Motivation

• Artists often deviate from linear projection
• Different projection for each object
• Curvilinear, nonlinear, inverted

• Express mood, feeling, idea

Five different projections
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Artistic Expression

• Viewing Anomalies
• Cezannes Still Life with Fruit Basket

Schematic from Loran (1943)
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Representation

• Reduce Wide-Angle Distortion
• Curved objects near camera appear distorted
• Row of columns (Leonardo da Vinci)

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Representation

• Reduce Wide-Angle Distortion
• Curved objects near camera appear distorted
• Row of columns (Leonardo da Vinci)

Multiple projections correct distortion
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Visualization

• Artificial Perspective
• Multiple parallel projections
• Orient receding parallel towards vanishing point
• Some area comparisons possible

53rd Street Map (Guarnaccia 93)
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Contributions

• Resolving visibility
• No well-defined visibility ordering
• Automatic methods
• Provide user control when necessary
• Camera constraints
• Camera placement image composition
• Animated effects (e.g. sprites)
• Interactive rendering
• Immediate feedback modeling much easier

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Video Part I
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Resolving Visibility

• Camera groups
• Local camera, geometry
• shape distortion
• image plane position
• Composite local images multiprojection image

Camera group A
Camera group B
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Depth-Based Compositing

• Warp local image pixels - master camera
• Apply standard z-buffer
• Does not always work as expected!

Multiprojection image
Master camera
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Multiprojection Depth-Compositing Only
Single Projection Master Camera View
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Multiprojection Depth-Compositing Only
Single Projection Master Camera View
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Object-Level Occlusion

• For each pair of objects compute occlusion
  constraints in master camera
• Ambiguities
• Convex hulls intersect (binary occlusion cycle)
• No interaction in master view
• Occlusion cycles (more than 2 objects)
• Fall back to depth-based compositing
• Allow user-specified occlusion constraints

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Visibility Algorithm

• Multipass
• Render each object with local and master camera
• Five camera groups, 402x491, 10-12 fps RE2

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Camera Constraints

• Object-Size
• Direct-Orientation
• Fixed-Position
• Fixed-View

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Video Part II
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Object Size

• Objects size (red) fixed as camera moves towards
  it
• Used in Hitchcocks Vertigo

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Direct - Orientation

• Point camera towards object (magenta)
• Maintain object position in image plane (cyan)

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Fixed - View

• Sprite like motion
• Image size (red)
• Image position (green)
• Orientation (magenta)

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Results Still Life

• Local cameras 10
• Setup 1 hour
• FPS 3-5

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Results Row of Columns
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Results de Chirico

• Setup
• Constraints very useful
• Match 20 minutes
• Animation 1 hour
• FPS 10-12
• Occlusions computed properly during animation

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Related Work

• Reducing distortion
• Theater (Dorsey 91), photo (Zorin 95), VR
  (Glaeser 99)
• Omnimax (Max 83)
• Generalized alternatives to linear projection
• Curvilinear, nonlinear, inverted, 3D warps,
  oblique
• (Inakage 91, Löffelmann 96, Levene 98)
• Multiple projections
• Löffelman manipulate rays in image space
• Levene local cam. (shape), master cam.
  (composition)

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Future Work

• Animation
• Sliding objects
• Flexible camera constraints
• Lighting
• Currently
• Lights defined in global scene
• Local images lit individually
• Shadows explicitly modeled
• Shadows, reflection, transparency?

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Conclusions

• Automatic visibility resolution
• Constraints to set camera parameters
• Interactive rendering
• Many applications
• Expression
• Representation
• Visualization

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Acknowledgements

• Pat Hanrahan
• Greg Niemeyer

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Representation I

• Best Views
• Large display billboard, mural
• Oblique viewing angle
• Wide range of viewpoints
• Application wall-sized displays

Paolo Uccelos Sir John Hawkwood
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Results City Overview
Multiple oblique projections
Standard perspective projection