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

or

Cortesia Alessi

Acquisition

Digital Shape

Acquisition & Reconstruction

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

Computer

restrictions

Restrictive

hypothesis 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)

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 largeamount 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,

…