Browsing by Author "Marroquim, R."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    ComVis‐Sail: Comparative Sailing Performance Visualization for Coaching
    (Eurographics ‐ The European Association for Computer Graphics and John Wiley & Sons Ltd., 2023) Pieras, M.; Marroquim, R.; Broekens, D.; Eisemann, E.; Vilanova, A.; Hauser, Helwig and Alliez, Pierre
    During training sessions, sailors rely on feedback provided by the coaches to reinforce their skills and improve their performance. Nowadays, the incorporation of sensors on the boats enables coaches to potentially provide more informed feedback to the sailors. A common exercise during practice sessions, consists of two boats of the same class, sailing side by side in a straight line with different boat handling techniques. Coaches try to understand which techniques are that make one boat go faster than the other. The analysis of the obtained data from the boats is challenging given its multi‐dimensional, time‐varying and spatial nature. At present, coaches only rely on aggregated statistics reducing the complexity of the data, hereby losing local and temporal information. We describe a new domain characterization and present a visualization design that allows coaches to analyse the data, structuring their analysis and explore the data from different perspectives. A central element of the tool is the glyph design to intuitively represent and aggregate multiple aspects of the sensor data. We have conducted multiple user studies with naive users, sailors and coaches to evaluate the design and potential of the overall tool.
  • Thumbnail Image
    Item
    Investigation and Simulation of Diffraction on Rough Surfaces
    (Eurographics ‐ The European Association for Computer Graphics and John Wiley & Sons Ltd., 2023) Clausen, O.; Chen, Y.; Fuhrmann, A.; Marroquim, R.; Hauser, Helwig and Alliez, Pierre
    Simulating light–matter interaction is a fundamental problem in computer graphics. A particular challenge is the simulation of light interaction with rough surfaces due to diffraction and multiple scattering phenomena. To properly model these phenomena, wave‐optics have to be considered. Nevertheless, the most accurate BRDF models, including wave‐optics, are computationally expensive, and the resulting renderings have not been systematically compared to real‐world measurements. This work sheds more light on reflectance variations due to surface roughness. More specifically, we look at wavelength shifts that lead to reddish and blueish appearances. These wavelength shifts have been scarcely reported in the literature, and, in this paper, we provide the first thorough analysis from precise measured data. We measured the spectral in‐plane BRDF of aluminium samples with varying roughness and further acquired the surface topography with a confocal microscope. The measurements show that the rough samples have, on average, a reddish and blueish appearance in the forward and back‐scattering, respectively. Our investigations conclude that this is a diffraction‐based effect that dominates the overall appearance of the samples. Simulations using a virtual gonioreflectometer further confirm our claims. We propose a linear model that can closely fit such phenomena, where the slope of the wavelength shifts depends on the incident and reflection direction. Based on these insights, we developed a simple BRDF model based on the Cook–Torrance model that considers such wavelength shifts.