Simulations of geothermal reservoirs inherently contain uncertainty due to
the fact that the underlying physical models are created from sparse data.
Moreover, this uncertainty often cannot be completely expressed by simple key
measures (e.g., mean and standard deviation), as the distribution of possible
values is often not unimodal. Nevertheless, existing visualizations of these
simulation data often completely neglect displaying the uncertainty, or are
limited to a mean/variance representation. We present an approach to
visualize geothermal simulation data that deals with both cases: scalar
uncertainties as well as general ensembles of data sets. Users can
interactively define two-dimensional transfer functions to visualize data and
uncertainty values directly, or browse a 2D scatter plot representation to
explore different possibilities in an ensemble.