Splotch: visualizing cosmological simulations

We present a light and fast, publicly available, ray-tracer Splotch software tool which supports the effective visualization of cosmological simulations data. We describe the algorithm it relies on, which is designed in order to deal with point-like data, optimizing the ray-tracing calculation by ordering the particles as a function of their 'depth', defined as a function of one of the coordinates or other associated parameters. Realistic three-dimensional impressions are reached through a composition of the final colour in each pixel properly calculating emission and absorption of individual volume elements. We describe several scientific as well as public applications realized with Splotch. We emphasize how different datasets and configurations lead to remarkably different results in terms of the images and animations. A few of these results are available online.