Computer Graphics recipes for analyzing and enhancing shape information Endowing 3D shapes with Semantics in Virtual Worlds Michela Mortara, Chiara Catalano, Bianca Falcidieno Shape Modelling Group CNR-IMATI Genova
Overview Basics on 3D digital shapes: Creation of a 3D model Representation of 3D models Not only geometry and graphics but knowledge carriers in many domains Endowing 3D models with semantics in Virtual Worlds: why and how Analysis of 3D models Annotation of 3D models and their components
Digital 3D Shapes 3D Models Single models Assemblies Environments
What are 3D models useful for? gradual shift of paradigm in science from physical prototypes and experience to virtual prototypes and simulation CAD/PLM Bioinformatics Medicine Cultural Heritage … 3D models in games: complex and convincing virtual worlds realistic environment and characters realistic interactions and behaviour
Trough a laser scanner a digital copy of the real object is made Using a modeler, the designer creates a digital objects from his/her idea Creation of a 3D model Cortesia Alessi
Acquisition Digital Shape Real object Laser Scanner Processing of the raw data to build up an accurate 3D model (meshing)
There are several steps to obtain the final model Several scans of the object must be acquired… The details of the process
There are several steps to obtain the final model Several scans of the object must be acquired… Then the scans must be aligned… The details of the process
There are several steps to obtain the final model Several scans of the object must be acquired… Then the scans must be aligned… The details of the process
There are several steps to obtain the final model Several scans of the object must be acquired… Then the scans must be aligned… And finally all the scans are merged into a single model The details of the process
There are several steps to obtain the final model Several scans of the object must be acquired… Then the scans must be aligned… And finally all the scans are merged into a single model The details of the process
Finally the post-processing: Geometric checks and repairing intersections, degeneracies, singularities, etc.) Hole filling Smoothing Simplification Textures ... The details of the process
Examples simplification resampling remeshing texturing
Mathematical Model Representation z = f(x,y) … Physical Object Digital Model Paradigm of Geometric Modelling Computer restrictions Restrictive hypothesis
Representation Schemes Boundary Schemes (e.g. meshes) Volumetric Schemes Decomposition Schemes Object-based (e.g. tetrahedrization) Spacial enumeration (e.g. voxelization) Constructive Schemes Based on half-spaces Based on Primitives (CSG)
Triangle meshes Mesh= V,E,T The representation is valid iff: Faces intersect only in common vertices or edges Face boundaries are simple (no auto-intersections) The mesh defines a solid which is closed, bounded and regular (no dangling entities)
3D and Technology today Technological advances highly reduced the costs of 3D content acquisition, storage and transmission But how to… organize, process, share, use and re-use, navigate, this large amount of complex content ? Are there similar objects in the repository? What is its functionality? #VRML V1.0 ascii Separator { Coordinate3 { point [ , , , , , …