  In the last decades cosmological N-body dark matter simulations have enabled
ab initio studies of the formation of structure in the Universe. Gravity
amplified small density fluctuations generated shortly after the Big Bang,
leading to the formation of galaxies in the cosmic web. These calculations have
led to a growing demand for methods to analyze time-dependent particle based
simulations. Rendering methods for such N-body simulation data usually employ
some kind of splatting approach via point based rendering primitives and
approximate the spatial distributions of physical quantities using kernel
interpolation techniques, common in SPH (Smoothed Particle
Hydrodynamics)-codes. This paper proposes three GPU-assisted rendering
approaches, based on a new, more accurate method to compute the physical
densities of dark matter simulation data. It uses full phase-space information
to generate a tetrahedral tessellation of the computational domain, with mesh
vertices defined by the simulation's dark matter particle positions. Over time
the mesh is deformed by gravitational forces, causing the tetrahedral cells to
warp and overlap. The new methods are well suited to visualize the cosmic web.
In particular they preserve caustics, regions of high density that emerge, when
several streams of dark matter particles share the same location in space,
indicating the formation of structures like sheets, filaments and halos. We
demonstrate the superior image quality of the new approaches in a comparison
with three standard rendering techniques for N-body simulation data.
