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Applications of Spectral Imaging and Reproduction to Cultural Heritage
Published in Filippo Stanco, Sebastiano Battiato, Giovanni Gallo, Digital Imaging for Cultural Heritage Preservation, 2017
Filippo Stanco, Sebastiano Battiato, Giovanni Gallo
The second class of reflection models are the empirical models. These models have been derived on well-fitting the BRDF without regarding the physical meaning of the parameters involved. The Phong reflection model [136] is the most popular reflection model in computer graphics. The model uses one parameter for the diffuse reflection component and two parameters for the specular reflections. Based on Phong’s model, Lafortune [137] proposed a model based on fitting the BRDF through the sums of cosine lobes. This model is able to represent complex effects such as retro- reflection and off-specular reflection. Finally, Ward [122] proposed an empirical model derived fitting the data measured by his gonioreflectometer.
The Effect of Interactive Cues on the Perception of Angiographic Volumes in Virtual Reality
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2021
Andrey Titov, Marta Kersten-Oertel, Simon Drouin
Shading is a photorealistic cue that simulates how an object reflects light when illuminated by a light source. One of the main advantages of this cue is that it is intuitive since it lets the viewer use knowledge about how objects are illuminated in real life. In the static version of shading, the light source is located at the midpoint between the two eyes, similarly to the light on a miner’s helmet. This way, the volume is always fully illuminated, no matter the position of the head in the virtual environment (see Figure 1(a)). In the dynamic version of shading, a point light source is attached to the tip of the pointer. Thus, as the user moves the pointer around the volume the anatomy around the pointer tip is illuminated and other parts of the volume fall into shadows. In other words, the light source works similarly to a match or flashlight that illuminates an object in a dark environment (see Figure 1(b)). The light source has a linear decay in intensity, which provides an additional cue for localisation of the pointer inside the volume. Shading was implemented using the Blinn-Phong reflection model (Blinn 1977)).