Trade-offs in appearance capture and representation by Tim Weyrich
Professor Weyrich introduces radiometry and appearance representations. Appearance is not restricted to the shape of an object, it is whatever influences light transport in a scene. The aspects of appearance can be labelled as geometry, surface structure and reflectance. Those are convenient parameters to manipulate when modelling a surface. However, effects take place at different scales and relate to different physical properties of an object.
Examples of Professor Weyrich’s work show different tradeoffs between capture and rendering, such as examples of human face acquisition and practical acquisition, balancing the needs of : acquisition time, accuracy and precision, cost and broadness of the class of surfaces being considered.
Modelling and predictive rendering of volumetric appearances by Adolfo Muñoz
Participating media such as the earth’s atmosphere interact with light as a volume. Light interacts differentially within such a medium, which yields beautiful effects such as sunbeams or rainbows. Other medias such as large bodies of water, candles, fire or even skin constitute participating media. Taking a step back from radiometry and considering light as an electromagnetic wave, we can consider the trajectory of light as a particle through a volume and therefore anticipate some particular phenomenons from quantum optics, wave optics or geometric optics.
One of the keys of volumetric appearance is using statistical physics instead of expensively modelling each particle individually. Statistical physics therefore need to define wether the properties of the medium are homogeneous or heterogeneous, isotropic or anisotropic, to then consider the absorption, emission and scattering occurring in the media.
Spectral rendering by Alexander Wilkie
These days displays translate colour values into images. Rendering computations that are done in colour values, can therefore be directly viewed on displays. However the end goal of rendering is the creation of realistic images and therefore doesn’t necessarily need to be restricted to colour values. Colour is a correlate of human perception but light transport can be done for any wavelength. Instead of using conventional colour space based renderers we can use spectral renderers, which enable us to look into wavelength-dependent optical effects such as polarisation, metamerism, structured colour, volume absorption, dispersion, interference, diffraction, fluorescence and phosphorescence.
