CSE 8031 Models and Matching Methods of modeling objects and their environments; Methods of matching models to sensed data for recogniton

CSE 8032 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)

CSE 8033 Models are what models do

CSE 8034 What do models do?

CSE 8035 Vertex-edge-face models Polyhedra and extensions; Model the surface of objects

CSE 8036 Vertex-Edge-Face model

CSE 8037 Sample object All surfaces are planar or cylindrical

CSE 8038 Matching methods Hypothesize point correspondences Filter on distances Compute 3D alignment of model to data Verify positions of other model points, edges, or faces. You can now do this! LOTS of work in the literature on this! Can work for many industrial objects (and human faces perhaps!)

CSE 8039 Triangular meshes Very general and used by most CAD systems.

CSE Texture-mapped mesh dog Courtesy of Kari Puli With 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. 3D SURFACE MODEL SURFACE PLUS TEXTURE

CSE Meshes are very general They are usually verbose and often are too detailed for many operations, but are often used in CAD. (Volumetric cube models are actually displayed here: made from many views by Kari Pulli.)

CSE Mesh characteristics + can be easy to generate from scanned data

CSE Making mesh models

CSE Marching cubes (James Sharman) "Marching Cubes: A High Resolution 3D Surface Construction Algorithm", William E. Lorensen and Harvey E. Cline, Computer Graphics (Proceedings of SIGGRAPH '87), Vol. 21, No. 4, pp Raster scan through image F(r, c). Look for adjacent pixels, one above threshold and one below threshold. Interpolate real coordinates for f(x, y) = t in between

CSE Marching in 3D space F(s, r, c) Some voxel corners are above threshold t and some are below.

CSE PhD work by Paul Albee 2004 Used Argonne National Labs scanner High energy, high resolution planar Xrays penetrate object rotating on a turntable Computer aided tomography synthesizes a 3D volume of densities with voxel size of about 5 microns

CSE Segmentation of Scutigera a tiny crablike organism Slice j of material density F( sj, r, c ) “ thresholded ” volume

CSE Some common 3D problems analyze blood vessel structure in head capture structure and motion of vertebrae of spine analyze porosity and structure of soil analyze structure of materials automatic segmentation into regions automatic correspondence of 3D points at two instants of of time 3D volume visualization and virtual tours

CSE Scanning technique abstraction CCD camera (row) material sample X-ray planes scintillator Pin head rotate X-rays partly absorbed by sample; excite scintillator producing one row in the camera image; rotate sample a few degrees and produce another row; 3D reconstruction using CT

CSE Scutigera: a tiny crustacean organism is smaller than 1 mm scanned at Argonne volume segmented and meshed by Paul Albee roughly ten million triangles to represent the surface anaglyph created for 3D visualization (view with stereo glasses)

CSE Presentation of Results to User Can explore the 3D data using rotation/translation Can create stereo images from 3D data

CSE Physics-based models Can be used to make meshes; Meshes retain perfect topology; Can span spots of bad or no data

CSE Physics-based modeling

CSE Forces move points on the model; halt at scanned data

CSE Fitting an active contour to image data

CSE Balloon model for closed object surface Courtesy of Chen and Medioni

CSE Balloon evolution balloon stops at data points mesh forces constrain neighbors large triangles split into 4 triangles resulting mesh has correct topology hard CS part is detecting when balloon should be stopped by data point

CSE Physics-based models Can also model dynamic behavior of solids (Finite Element Methods)

CSE Tagged MRI: 3D interest points can be written to body! The MRI sensor tags living tissue and can sense its movement. Motion of a 3D tetrahedral finite elements model can then be analyzed. FMA model attempts to model the real physics of the heart. Work by Jinah Park and Dimitry Metaxes.

CSE 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

CSE The octree for compression

CSE Generalized cylinders

CSE 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

CSE Extracting a model from a segmented image region Courtesy of Chen and Medioni

CSE 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?

CSE 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.

CSE Generalized cylinders

CSE View class models Objects modeled by the distinct views that they can produce

CSE “ aspect model ” of a cube

CSE Recognition using an aspect model

CSE View class model of chair 2D Graph-matching (as in Ch 11) used to evaluate match.

CSE 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.

CSE Matching image edges to model limbs Could recognize car model at stoplight or gate or in car wash.

CSE Appearance-based models Using a basis of sub images; Using PCA to compress bases; Eigenfaces (see older.pdf slides 14C)

CSE 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.)

CSE Louise Stark: chair model Dozens of CAD models of chairs Program analyzes model for * stable pose * seat of right size * height off ground right size * no obstruction to body on seat * program would accept a trash can (which could also pass as a container)

CSE 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, …