Imagebased Building Shadow Generation by Shape from Shadow Silhouette Technique

1
Image-based Building Shadow Generation by Shape
from Shadow Silhouette Technique

• Xiaohui ZHANG
• Nakajima Lab
• Graduate School of Information Science
  Engineering
• Tokyo Institute of Technology

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Contents

• Background and related work
• Features of building shadow
• Shape from shadow silhouette
• Experiment result
• Conclusion and future work

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Image-based Daylight Lighting
Image-based Rendering
Fixed View
Image-based Daylight Lighting
Fixed Lighting
4
Image-based Daylight Lighting
Lighting
Shadow
Color
5
Objective
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Related Work

• Kohei Terazono, Yoshitsugu Manabe, Seiji
  Inokuchi, Shadow Image Generation on Image based
  Rendering , IEICE General Conference,1999,
  D-12-145
• W.N.Martin and J.K.Affarwal, Volumetric
  Descriptions of Objects from Multiple Views, IEEE
  Trans. PAMI 5(2), pp.150-158, 1983
• Xiaohui ZHANG and Masayuki NAKAJIMA, Image-based
  Tree Shadow Morphing Technique, The Journal of
  the Institute of Image Electronics Engineers of
  Japan, Vol.28, No.5, 2000

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Building Shadow Features
The Sun

• The outline is almost
• regular line
• No holes
• shape of shadow
• changes dramatically

SSD

• Man-made objects
• Constituted by primitives
• such as cube, cylinder
• Building shadow is the
• silhouette from the
• direction of the sunlight

shadow surface
SSD Sun Shadow Direction, the
direction of an erect straight pole shadow
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Shape from Silhouette (1)
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Shape from Silhouette (2)
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Shape from Shadow Silhouette (SFSS)
Shadow Silhouettes
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Shape from Shadow Silhouette (SFSS)
SFSS
Shadow shape
Shadow Silhouettes
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Shape from Shadow Silhouette (SFSS)
SFSS
Shadow shape
Shadow Silhouettes
Projection
Novel Shadow
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Difference from Shape from Silhouette

• The projection direction
• is determined by the sun
• movement
• The shadow silhouette is
• not a complete silhouette

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Image-based Building Shadow Generation Flow Chart
Pre-process
Shadow Extraction
Perspective Transform
SFSS
Auxiliary Shadow Generation
Shape modeling
Novel Shadow Generation
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Ground Shadow Extraction (1)
Image in the morning
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Ground Shadow Extraction (1)
Image in the afternoon
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Ground Shadow Extraction (3)
Perspective Transformation
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Auxiliary Shadow Generation
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Auxiliary Shadow Generation
SSD
apex
axis
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Auxiliary Shadow Generation
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Shape Modeling
3D Volume
Shadow volume voxel
Not shadow volume voxel
Auxiliary shadow
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Novel Shadow Generation
New Sun Position
Shadow volume
projection
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Novel Shadow Generation
New Sun Position
Shadow volume
projection
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Novel Shadow Generation
New Sun Position
Shadow volume
projection
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Novel Shadow Generation
New Sun Position
Shadow volume
projection
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Novel Shadow Generation
New Sun Position
Shadow volume
projection
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Novel Shadow Generation
New Sun Position
Shadow volume
projection
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Experimental Results (1)
1100am
900am
1000am
1400pm
1500pm
1300pm
Reference Images
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Experimental Results (2)
Shadow Volume
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New Shadow
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Error
930am
1030am
1330pm
1430pm
Generated new shadow
1430pm
1030am
1330pm
930am
Error images
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Conclusion

• Shape from shadow silhouette is proposed
• Shadow shape is abstracted from shadow silhouette
  
• Shadow on the ground surface can be generated
  quickly and correctly

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Future Work

• Shadow on other object surface
• Image-based shadow generation method for other
  objects