Introduction
The Volume Haptics Toolkit provides an extension of the H3D
API into the domain of volumetric data. The toolkit provides the
scene-graph nodes needed to generate both advanced haptic feedback
from volumetric data and for producing scientific visual rendering.
Primarily the haptic algorithms provided by the toolkit are designed
to provide natural representations of information from scientific
volumetric data and to provide guidance in the exploration process.
The methods are, however, very general and can also be used for other
purposes, for example to generate guidance fields in games or
alternative tasks.
The toolkit is based on the results from four years of research on
haptics for scientific visualization. These results include the
development of haptic primitives that in the toolkit are used both as
a comprehensive abstraction layer for implementing haptic interaction
and as an effective means for stable calculation of the haptic
feedback. The research has also identified important aspects and
outlined the guidelines needed for successful implementation of
effective haptic interaction in scientific data exploration. These
aspects and guidelines have been carefully adhered in the development
of VHTK to make it easy to build both prototypes and advanced
applications.
The special features of this toolkit, that have been introduced
through the implementation of research results, include
- ...off-the-shelf combinable active and passive metaphores
- ...readily available haptic modes for representing both scalar
and vector data, both continuous and sampled
- ...consistent feedback from any combination of active and
passive metaphores for haptic interaction
- ...consistent feedback from both moving, through dynamic
transforms, and animated volumetric data
- ...haptic interpolation to allow for smooth haptic palpation
even of low frame-rate volumetric animation
To enable the interactive construction of the haptic environment
needed for the effective design of the form of interaction, the
toolkit is built on the concept of a configurable data flow pipeline.
In this model, shown in the figure, the features of interest are
extracted from the data at real-time. Haptic transfer functions are
used to extract material information from the data, such as friction
or hardness. The feature and material information are used to control
haptic primitives. The primitives, specifying the form and nature of
the haptic feedback, are collected by a force mapper that calculates
the final force feedback that is, in turn, sent to the haptic device,
typically at a rate of 1 kHz. Both haptic and visual components
can be interactively manipulated at run-time through the event system
of H3D.
See documentation for more details.
