Author(s):
Santos, Luís Paulo 
; Coelho, Vítor ; Bernardes, P. ; Proença, Alberto José
Date: 2005
Persistent ID: http://hdl.handle.net/1822/3513
Origin: RepositóriUM - Universidade do Minho
Subject(s): Distributed network graphics; Ray tracing; Archaeology
Description
Comunicação apresentada no 6th International Symposium on Virtual Reality, Archaeology and Cultural Heritage (VAST 2005), Pisa, Italy, 8-11 Novembro 2005. Fast and affordable computing systems currently support walkthroughs into virtual reconstructed sites, with fast frame
rate generation of synthetic images. However, archaeologists still complain about the lack of realism in these interactive tours,
mainly due to the false ambient illumination. Accurate visualizations require physically based global illumination models
to render the scenes, which are computationally too demanding.
Faster systems and novel rendering techniques are required: current clusters provide a feasible and
affordable path towards these goals, and we developed a framework to support smooth virtual walkthroughs,
using progressive rendering to converge to high fidelity images whenever computing power surplus is available.
This framework exploits spatial and temporal coherence among
successive frames, serving multiple clients that share and
interact with the same virtual model, while maintaining each its
own view of the model. It is based on a three-tier architecture:
the outer layer embodies light-weight visualization clients, which
perform all the user interactions and display the final images
using the available graphics hardware; the inner layer is a
parallel version of a physically based ray tracer running on a
cluster of off-the-shelf PCs; in the middle layer lies the shading
management agent (SMA), which monitors the clients' states,
supplies each with properly shaded 3D points, maintains a cache of
previously rendered geometry and requests relevant shading samples
to the parallel renderer, whenever required.
A prototype of a high fidelity walkthrough in the archaeologic
virtual model of the roman town of Bracara Augusta was developed,
and the current evaluation tests aimed to measure the performance
improvements due to the use of SMA caches and associated parallel
rendering capabilities. Preliminary results show that interactive
frame rates are sustainable and the system is highly responsive.
