stockman cse/msu fall 2005 models and matching methods of modeling objects and their environments;...
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Stockman CSE/MSU Fall 2005
Models and Matching
Methods of modeling objects and their environments;
Methods of matching models to sensed data for recogniton
Stockman CSE/MSU Fall 2005
Some methods to study Mesh models (surface) Vertex-edge-face models (surface) Functional forms: superquadrics (surface) Generalized cylinders (volume) Voxel sets and octrees (volume) View class models (image-based) Recognition by appearance (image-based) Functional models and the Theory of
affordances (object-oriented)
Stockman CSE/MSU Fall 2005
Models are what models do
Stockman CSE/MSU Fall 2005
What do models do?
Stockman CSE/MSU Fall 2005
Vertex-edge-face models
Polyhedra and extensions
Stockman CSE/MSU Fall 2005
Vertex-Edge-Face model
Stockman CSE/MSU Fall 2005
Sample object
All surfaces are planar or cylindrical
Stockman CSE/MSU Fall 2005
Matching methods Hypothesize point correspondences Filter on distances Compute 3D alignment of model to
data Verify positions of other model
points, edges, or faces LOTS of work in the literature on this!
Can work for many industrial objects (and human faces perhaps!)
Stockman CSE/MSU Fall 2005
Triangular meshes
Stockman CSE/MSU Fall 2005
Texture-mapped mesh dog
Courtesy of Kari PuliWith each triangle is a mapping of its vertices into pixels [r, c] of a color image. Thus any point of any triangle can be assigned a color [R, G, B]. There may be several images available to create these mappings.
Stockman CSE/MSU Fall 2005
Meshes are very general
They are usually verbose and often are too detailed for many operations, but are often used in CAD
Stockman CSE/MSU Fall 2005
Modeling the human body for clothing industry and …
Multiple Structured light scanners used: could this be a service industry such as Kinkos?
Actually cross sections of a generalized cylinder model.
Stockman CSE/MSU Fall 2005
Mesh characteristics
+ can be easy to generate from scanned data
Stockman CSE/MSU Fall 2005
Making mesh models
Stockman CSE/MSU Fall 2005
Physics-based models
Can be used to make meshes;Meshes retain perfect
topology;Can span spots of bad or no
data
Stockman CSE/MSU Fall 2005
Physics-based modeling
Stockman CSE/MSU Fall 2005
Forces move points on the model; halt at scanned data
Stockman CSE/MSU Fall 2005
Fitting an active contour to image data
Stockman CSE/MSU Fall 2005
Balloon model for closed object surface
Courtesy of Chen and Medioni
Stockman CSE/MSU Fall 2005
Balloon evolution• balloon stops at data points
• mesh forces constrain neighbors
• large triangles split into 4 triangles
• resulting mesh has correct topology
Stockman CSE/MSU Fall 2005
Physics-based models
Can also model dynamic behavior of solids (Finite Element Methods)
Stockman CSE/MSU Fall 2005
Algorithms from computer graphics make mesh models from blobs
Marching squares applied to some connected image region (blob)
Marching cubes applied to some connected set of voxels (blob)
See a CG text for algorithms: see the visualization toolkit for software
Stockman CSE/MSU Fall 2005
Volume model: voxels, octrees
Stockman CSE/MSU Fall 2005
Simple object and its octree
Stockman CSE/MSU Fall 2005
Generalized cylinders
Stockman CSE/MSU Fall 2005
Generalized cylinders
• component parts have axis
• cross section function describes variation along axis
• good for articulated objects, such as animals, tools
• can be extracted from intensity images with difficulty
Stockman CSE/MSU Fall 2005
Extracting a model from a segmented image region
Courtesy of Chen and Medioni
Stockman CSE/MSU Fall 2005
Interpreting frames from video
Can we match a frame region to a model?
What about a sequence of frames? Can we determine what actions
the body is doing?
Stockman CSE/MSU Fall 2005
Generalized cylinders
Stockman CSE/MSU Fall 2005
View class models
Objects modeled by the distinct views that they can
produce
Stockman CSE/MSU Fall 2005
“aspect model” of a cube
Stockman CSE/MSU Fall 2005
Recognition using an aspect model
Stockman CSE/MSU Fall 2005
View class model of chair
2D Graph-matching (as in Ch 11) used to evaluate match.
Stockman CSE/MSU Fall 2005
Side view classes of Ford Taurus (Chen and Stockman)
These were made in the PRIP Lab from a scale model.
Viewpoints in between can be generated from x and y curvature stored on boundary.
Viewpoints matched to real image boundaries via optimization.
Stockman CSE/MSU Fall 2005
Matching image edges to model limbs
Could recognize car model at stoplight or gate.
Stockman CSE/MSU Fall 2005
Appearance-based models
Using a basis of sub images;Using PCA to compress bases;
Eigenfaces (see older .pdf slides 14C)
Stockman CSE/MSU Fall 2005
Function-based modeling
Object-oriented;What parts does the object have;
What behaviors does it have;What can be done with it?
(See plastic slides of Louise Starks’s work.)
Stockman CSE/MSU Fall 2005
Theory of affordances: J.J. Gibson
An object can be “sittable”: a large number of chair types, a box of certain size, a trash can turned over, …
An object can be “walkable”: the floor, ground, thick ice, bridge, ...
An object can be a “container”: a cup, a hat, a barrel, a box, …
An object can be “throwable”: a ball, a book, a coin, an apple, a small chair, …