Interactive Volume Rendering in a VRML Environment

J. Liao and I. Gargantini (Canada)


Volume Rendering, VRML, EAI,Dynamic Transparency.


A platform-independent system, called VRML Through Viewer, has been designed and implemented. Volumes are visualized in an interactive environment that allows a user to control the depth at which to penetrate inside the volume. The system is based on an innovative approach to ray casting that incorporates different techniques: adoption of a distance transform to skip empty regions, traversal of object space only to avoid repetitive mappings from and to image space, simplification of the formulas that combine shading with opacity, early ray termination and dynamic transparency. An implementation of VRML Through Viewer is also given, which provides animation via VRML; encapsulates parameters changes and ray casting in a Java applet via EAI; and establishes communication among the different modules by using the External Authoring Interface (EAI). VRML Through Viewer can download volume data and the program from a central site, while its visualization (with different parameters) can take place on any number of PC spread around the globe. The system has been tested on several 3D images and changing viewpoints with data of up to 15 MB.

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