Georg Zotti

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The Preetham skylight model is currently one of the most widely used analytic models of skylight lumi-nance in computer graphics. Despite its widespread use, very little work has been carried out to verify the results generated by the model, both in terms of the luminance patterns it generates, and in terms of numerical reliability and stability. In this(More)
This paper describes an accurate method to obtain the Tone Reproduction Curve (TRC) of display devices without using a measurement device. It is an improvement of an existing technique based on human observation, solving its problem of numerical instability and resulting in functions in log–log scale which correspond better to the nature of display devices.(More)
Under certain circumstances the polarisation state of the illumination can have a significant influence on the appearance of scenes; outdoor scenes with specular surfaces – such as water bodies or windows – under clear, blue skies are good examples of such environments. In cases like that it can be essential to use a polarising renderer if a true prediction(More)
This paper describes a simple to use, yet accurate way to obtain the Tone Reproduction Curve (TRC) of display devices without the use of a measurement device. Human vision is used to compare a series of dithered color patches against interactively changeable homogeneously colored display areas. Results comparing this method with spectropho-tometer(More)
Figure 1: Virtual reconstruction of a look through one of the doors in the neolithic Kreisgrabenanlage of Steinabrunn in Lower Austria. The singular post appears to be aligned to the rising point of the Pleiades star cluster, which with their rising in the morning possibly announced the beginning of the agricultural year. Astronomical alignments like this(More)
We discuss the validation of BTF data measurements by means used for BRDF measurements. First, we show how to apply the Helmholtz reciprocity and isotropy for a single data set. Second, we discuss a cross-validation for BRDF measurement data obtained from two different measurement setups, where the measurements are not calibrated or the level of accuracy is(More)
In the last decades, archaeologists in central Europe have found traces of enigmatic neolithic circular building structures buried in the soil. Recent studies indicate that the orientation of many of their doorways may have been chosen with an astronomical background in mind. This paper explains the use of virtual reconstructions of these buildings from(More)