Tour Into the Picture:Using a Spidery Mesh to Make Animation from a Single
Image
Youichi Horry, Ken-ichi Anjyo, and Kiyoshi Arai
SIGGRAPH 1997
presented by Dave Edwards10/31/2000
A Unique Problem
Can we create animation from a single image? Paintings Single photographs
Extremely difficult for a computer No information for depth or 3D structure
Not as difficult for a human brain
A Unique Solution
A system that allows humans and computers to do what they do best Human supplies 3D scene information Computer supplies efficient interface
for:Specifying vanishing pointsDifferentiating foreground & backgroundBuilding the scene with simple polygons
Tour Into the Picture (TIP)
System that allows efficient specification of 3D information
Basically, construct a diorama-like model of the scene Simple, generic representation
5 (or fewer) polygons for backgroundSmall number of polygons for each
foreground object
Overview
Scene modeling Separate foreground & background Specify a vanishing point Model the background Model foreground objects
Scene animation & renderingConclusionsDemo
Scene Modeling
Assumptions Scene is basically a box Sides of the box are orthogonal to each
other Virtual camera may not be tilted
View up vector is perpendicular to “floor”
Separate Fore- & Background
Start with a single image:
Separate Fore- & Background
Create two images with standard image editor
Foreground mask: One gray region for each object Grayscale map of alpha values
Background image: Original image w/o foreground Use neighboring pixels to fill gaps
Separate Fore- & Background
Example foreground mask:
Separate Fore- & Background
Example background image:
Specify a Vanishing Point
Use a “spidery mesh” Inner rectangle
Specifies “rear wall” of scene
Radial perspective linesSpecify the location of the vanishing pointShould be parallel to guide lines in the
picture
Interface allows rapid changes in the mesh
Specify a Vanishing Point
Example of Interface:
Model the Background
Partition the background into 5 pieces: Rear wall (inner rectangle) Floor (y = 0) Ceiling Left Wall Right Wall
Calculate 3D coords for the vertices of the box
Model the Background
Example of background model:
Model the Foreground
Foreground objects defined by maskConstruct polygon model of each
object Must be orthogonal to one side of the box Calculate 3D coords for corners of
polygon
Model the Foreground
More complex objects can be made of multiple polygons Each additional polygon must be
connected to the previous one This allows the system to determine its
3D coordinates
Model the Foreground
Example of foreground model:
Scene Animation & Rendering
Camera transformations: Rotation (change view-plane normal) Translation Zoom (move viewpoint forward) Change view angle Look around (orbit about central object)
Scene Animation & Rendering
We know 3D coordinates for points in the scene
Given a pixel to render, find its 3D image in the original scene
Apply smoothing for the backgroundApply alpha blending for the
foreground objects
Conclusions
TIP is very flexible In general, assumptions do not create
severe constraints Generic foreground/background model
works with many types of imagesInterface is (fairly) simple & intuitive,
even in the demo version It could use a little internationalization...
Future Possibilities
Handle two-point perspective drawings
Allow multiresolution images
Improve the model for foreground objects
Demonstration
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