Rapid Shadow Generation in Real-World Lighting Environments
Simon Gibson, Jon Cook, Toby Howard, Roger Hubbold.
Rendering Techniques 2003 (Proceedings of the Eurographics Symposium
on Rendering), Leuven, Belgium, June 2003 (to appear).
Abstract
We propose a new algorithm that uses consumer-level graphics hardware
to render shadows cast by synthetic objects and a real lighting
environment. This has immediate benefit for interactive Augmented
Reality applications, where synthetic objects must be accurately
merged with real images. We show how soft shadows cast by direct and
indirect illumination sources may be generated and composited into a
background image at interactive rates. We describe how the sources of
light (and hence shadow) affecting each point in an image can be
efficiently encoded using a hierarchical shaft-based subdivision of
line-space. This subdivision is then used to determine the sources of
light that are occluded by synthetic objects, and we show how the
contributions from these sources may be removed from a background
image using facilities available on modern graphics hardware. A
trade-off may be made at run-time between shadow accuracy and
rendering cost, converging towards a result that is subjectively
similar to that obtained using ray-tracing based differential
rendering algorithms. Examples of the proposed technique are given for
a variety of different lighting environments, and the visual fidelity
of images generated by our algorithm is compared to both real
photographs and synthetic images generated using non-real-time
techniques.
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