Cosmological simulations follow the formation of nonlinear structure in dark and luminous matter. The associated simulation volumes and dynamic range are very large, making visualization both a necessary and challenging aspect of the analysis of these datasets. Our goal is to understand sources of inconsistency between different simulation codes that are started from the same initial conditions. Quantitative visualization supports the definition and reasoning about analytically defined features of interest. Comparative visualization supports the ability to visually study, side by side, multiple related visualizations of these simulations. For instance, a scientist can visually distinguish that there are fewer halos (localized lumps of tracer particles) in low-density regions for one simulation code out of a collection. This qualitative result will enable the scientist to develop a hypothesis, such as loss of halos in low-density regions due to limited resolution, to explain the inconsistency between the different simulations. Quantitative support then allows one to confirm or reject the hypothesis. If the hypothesis is rejected, this step may lead to new insights and a new hypothesis, not available from the purely qualitative analysis. In this presentation, I will present methods to significantly improve the scientific analysis process by incorporating quantitative analysis as the driver for visualization. Aspects of this work are included as part of two visualization packages, ParaView, an open-source large data visualization package and Scout, an analysis-language based, hardware-accelerated visualization package.
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| Cosmological simulation of structure formation with warm dark matter (WDM). In WDM scenarios, small-scale fluctuations are suppressed. Conventional methods applied to WDM initial conditions suffer from grid artifacts which are difficult to see quantitatively but are apparent visually. The linear alignment of halos in filaments shown clearly in the figure -- the string of pearls effect -- is one such artifact. |