1. 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

2. 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

3. Digital 3D Shapes  3D Models  Single models  Assemblies  Environments

4. 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

5. 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

6. Acquisition Digital Shape Real object Laser Scanner Processing of the raw data to build up an accurate 3D model (meshing)

7.  There are several steps to obtain the final model  Several scans of the object must be acquired… The details of the process

8.  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

9.  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

10.  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

11.  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

12.  Finally the post-processing:  Geometric checks and repairing  intersections, degeneracies, singularities, etc.)  Hole filling  Smoothing  Simplification  Textures ... The details of the process

13. Examples simplification resampling remeshing texturing

14. Mathematical Model Representation z = f(x,y) … Physical Object Digital Model Paradigm of Geometric Modelling Computer restrictions Restrictive hypothesis

15. 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)

16. 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)

17. 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 [ -1.595000 -1.101000 4.897000, -1.537000 -0.933000 4.899000, -1.681000 -0.995000 4.885000, -1.712000 -0.948000 4.876000, -1.589000 -0.765000 4.893000, …