CG Colloquium Thursday February 21st

You are cordially invited to attend our Computer Graphics and Visualization Seminar on Thursday, February 21, 2019, 15:45-17:45h, at EWI-Lecture hall Chip.

The program features the following two speakers:

Nouri Khalass
Title: Visualizing Stars and Emission Nebulae
Abstract: We describe the star and nebula visualization techniques used to create a 3D volumetric visualization of the Orion Nebula. The nebula’s ionization layer is modeled first as a surface model, derived from infrared and visible light observations. The model is imported into a volume scene graph-based volume visualization system to simulate the nebula’s emissive gases. Stars are rendered using Gaussian spots that are attenuated with distance.

Mark van de Ruit
Title: Real-Time Polygonal-Light Shading with Linearly Transformed Cosines
Abstract: In this paper, we show that applying a linear transformation—represented by a 3 x 3 matrix—to the direction vectors of a spherical distribution yields another spherical distribution, for which we derive a closed-form expression. With this idea, we can use any spherical distribution as a base shape to create a new family of spherical distributions with parametric roughness, elliptic anisotropy and skewness. If the original distribution has an analytic expression, normalization, integration over spherical polygons, and importance sampling, then these properties are inherited by the linearly transformed distributions.

By choosing a clamped cosine for the original distribution we obtain a family of distributions, which we call Linearly Transformed Cosines (LTCs), that provide a good approximation to physically based BRDFs and that can be analytically integrated over arbitrary spherical polygons. We show how to use these properties in a realtime polygonal-light shading application. Our technique is robust, fast, accurate and simple to implement.