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2-Phase Direct Volume Rendering


The plume data describes the effective scattering strength of the particles suspended in the seawater, this is used as a proxy for the density distribution of particles. Rendering of such complex participating media realistically as well as efficiently is an ongoing research problem. Note that we do not try to reproduce photos as the scale of photos is 1-2m, much smaller than the scale of the acoustic data 30-100m. We rendered a number of acoustic plume datasets using iso-surface rendering, single phase direct volume rendering (DVR), and two-phase DVR. 
In this work, we show that one can perceive vertical expansion better by using a more optically-based rendering method that is able to convey the effects of scattering and shadows in the plume and surrounding water. Even for cameras and lights that are specially designed to function in a harsh seafloor environment, the the tendency of water to absorb visible light sharply limits the visible area to a 2-5m wide viewing area. The acoustic data captures a 16m x 16m x 30m volume or larger, penetrating into the more dilute (and less wispier) regions of the plumes. Our primary goal is to best illustrate the expansion of the plumes and what enhancements would make viewing this data most useful, especially to scientists who want to anaylze the plume.
The expansion rate of the plume is an important physical characteristic of the plume. It is strongly related to other features of interest to the scientists, such as the density and the mixing rate. The silhouette comparison shows qualitatively the significant improvement of the visible expansion in the results of the two-phase DVR method over the coventional isosurfacing and single-phase DVR methods.The result of the two-phase DVR correlate more closely with the numerical anaylsis of the expansion than the other two methods. Through this application, we introduce a methodology for validating visualization results through quantitative comparison of expansion characteristics in data and visualization.
The particles in hydrothermal plumes depend on the chemistry and temperature of the fluid exiting the seafloor. High temperature fluids from black smokers are typically charcterized by the precipitation of metal rich sulfide and sulfate minerals (e.g., chalcopyrite, pyrrhotite, pyrite, sphalerite) while low temperature fluids from white smokers typcally precipitate amorphous silica, pyrite and barite. In order to incorporate the spectral response of these minerals into the visualization process, we implemented a spectral version of the two-phase DVR to render the acoustic data.
If you are interested in trying the 2-Phase Direct Volume Rendering Code please e-mail: Karen Bemis ( or Jay Takle (
Note: The 2 Phase Direct Volume Rendering Code works on only a Unix or Linux based operating system.

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