ExRealis

IGG's digitization platform

The goal of this platform is to offer a certain number of techniques (hardware and software) allowing to acquire 3D objects with visual appearance or complex materials for applications in computer-generated pictures and virtual reality.

Instead of having a person who creates a polygonal model of an existing object, we wish to be able to directly acquire this model from reality. Nowadays there are many existing techniques and equipments (e.g. 3D scanners) allowing to digitize. But these techniques often have strong limitations: their use requires a high degree of expertise, several steps require tedious manual interventions, the resulting models are huge and impossible to render in real-time directly on the GPU, etc.

IGG's digitization platform covers the three following aspects:

• acquisition of models with visual appearance from dedicated devices,
• automatic (or semi-automatic) treatments of models (registration, filtering, fusion, reconstruction, simplification and representation tuned for the application),
• specific rendering tools on the GPU.

Equipments and software

Optical scanner by projection of fringes and phase shift measuring.

This device allows the 3D acquisition of objects of a size between approximately 10 and 50cm. An external video camera allows to perform an automatic registration of several exposures and also the superposition of information concerning the RGB colored directional appearance. A specific software has been developed in order to make acquisitions and restoration on screen.

Goniometer.

This device allows the positioning of a light source on a hemispheric dome in order to vary the lighting of a 3D object or of a aterial sample (whose size is between 10 and 20cm). This device will be completed at the end of 2009 by a second mobile rotating arch to allow the positioning of a video camera on a hemispheric dome.

This device, though yet incomplete, has been used for the acquisition of paintings using bidirectional texture function.

An example of painting digitization:

The left picture shows a photo of a painting, the center image, a computer-generated rendering for the same point of view by using a texture mapping of classical colors, and the right image, by using a bidirectional texture function from which the relief has been decoupled from the bidirectional reflectance.

Mid-range laser scanner.

It consists of a laser ScanStation2 from Leica Geosystems. It allows to perform scans on a range of 0.2-300m with a speed of up to 50000 points/sec. A target set also allows to perform registration. See also the data sheet (in french) of Leica Geosystems.

Collaborations

• IGG's digitization platform takes place in the plateform of digitization and 3D modeling (in french) of Université de Strasbourg.
• Several national and regional projects are associated to this plateform: ANR ATROCO, Ministry RIAM AMI3D, Region "Pôle Image".