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Shader Techniques for VEs - Shadows and NPR

Möglichkeiten der Schattendarstellung unter OpenGl, Performer und Avango ( Possibilities of displaying shadows using OpenGL, Performer and Avango)

Shadows appear, when there is an object blocking the light, so the whole region behind this shadow caster could not be lit by the light source. This omnipresent effect makes the shape and relative position of objects in such scenes more comprehensible and helps us to identify the distribution of light sources. In computer graphics this is not necessarily  true because this familia effect doesn’t appear automatically but must involved imitated.

In virtual reality applications ("’VR"’) it is very important to make an artificial world believable, so it will be accepted by the user as natural. The more the world is closer to reality, the more it fulfil its task to lead the user to believe in it and the easier it is to navigate through it. Shadows are one way to reach this goal.

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When todays used shadow techniques were invented nearly 30 years ago, they were to expensive in calculation to be used in interactive applications. Nowadays every computer game uses shadows, which becomes possible with the upcoming of programmable graphics hardware for the consumer market at moderate prices. Unfortunately in VR, where shadows could really help the acceptance as natural for the user,  shadows are no standard.

To fill this gap, my task was to implement both popular shadow generating methods, that is Shadow Mapping and Stencil Shadow Volumes, for the virtual reality framework avango. Like many other VR frameworls, it uses a scene graph to organize the artificial world.  The used scene graph is OpenGL Performer which was developed by "Silicon Graphics".  So the first step was the implementation for Performer to prove the possibilitiy use these shadow generating methods for a scene graph based system.  It turned out that it is possible and moreover it can be converted also for avango.



Papers


Generation of Shadows in Scene Graphs based VR

Kühl, B., Blom, K., Beckhaus, S.
The 15-th International Conference in Central Europe on Computer Graphics, Visualization and Computer Vision'2007 (WSCG' 2007)
Plzen, Czech Republic
Full Paper, pg. 295-302, ISBN 978-80-86943-98-5
File(s): Paper (PDF)


People involved:

Björn Kühl, Alexej Fink, Steffi Beckhaus, Kristopher J. Blom