Kévin Boulanger

A directional occlusion shading model for interactive direct volume rendering

Volumetric rendering is widely used to examine 3D scalar fields from CT/MRI scanners and numerical simulation datasets. One key aspect of volumetric rendering is the ability to provide perceptual cues to aid in understanding structure contained in the data. While shading models that reproduce natural lighting conditions have been shown to better convey depth information and spatial relationships, they traditionally require considerable (pre)computation. In this paper, a shading model for interactive direct volume rendering is proposed that provides perceptual cues similar to those of ambient occlusion, for both solid and transparent surface‐like features. An image space occlusion factor is derived from the radiative transport equation based on a specialized phase function. The method does not rely on any precomputation and thus allows for interactive explorations of volumetric data sets via on‐the‐fly editing of the shading model parameters or (multi‐dimensional) transfer functions while modifications to the volume via clipping planes are incorporated into the resulting occlusion‐based shading.

ATIP: A Tool for 3D Navigation inside a Single Image with Automatic Camera Calibration

Automatic Tour Into the Picture (ATIP) is an extension of the Tour Into the Pic ture method [ HAA97] that allows an approximative but visually convincing 3D walk-through inside a single ima ge by rendering a box textured using the input image data. The original algorithm requires a long and tedious use r int raction to determine the box dimensions and the perspective parameters, and imposes several con straints on the input image orientation. The goal of this paper is to present a framework providing fully automatic and fas t c mera calibration for any view orientation without using a calibration target. Our method reduces the user in t action, hence only a couple of seconds are required between the input image loading and the final walkthrough.

Rendering Grass in Real Time with Dynamic Lighting

The authors present a real-time grass rendering technique that works for large, arbitrary terrains with dynamic lighting, shadows, and a good parallax effect. A novel combination of geometry and lit volume slices provides accurate, per-pixel lighting. A fast grass-density management scheme allows the rendering of arbitrarily shaped patches of grass.

Cross-modal affects of smell on the real-time rendering of grass

Smell is a key human sense which can significantly effect our perception of an environment. Although, typically not as developed as our other senses, the presence of a pleasant or unpleasant smell can alter the way we view a scene. Such a cross-modal effect can be substantial with parts of a scene literally going unnoticed as the smell dominates our senses. This paper investigates the cross-modal affect on the perception of the real-time animation of a field of grass in the presence of the smell of cut-grass. Rendering the high level of detail of a close-up view of a field of grass is computationally very demanding. In the real world the smell of grass would be present, and especially strong if the grass had just been cut, for example in preparation for a sports event. By exploiting the cross-modal interaction between smell and visuals we are able to render a lower quality version of a field of grass at a reduced computational cost, without the viewer being aware of the quality difference compared to a high quality version.

Rendering trees with indirect lighting in real time

High quality lighting is one of the challenges for interactive tree rendering. To this end, this paper presents a lighting model allowing real‐time rendering of trees with convincing indirect lighting. Rather than defining an empirical model to mimic lighting of real trees, we work at a lower level by modeling the spatial distribution of leaves and by assigning them probabilistic properties. We focus mainly on precise low‐frequency lighting that our eyes are more sensitive to and we add high‐frequency details afterwards. The resulting model is efficient and simple to implement on a GPU.

High-Frequency Shadows for Real-Time Rendering of Trees

Abstract We present a fast and simple method for adding high-frequency shadows into the foliage of trees rendered in real-time. When leaves of a tree project shadows onto other leaves, determining the relationships between cast shadows and the corresponding occluders is a visually difficult task. We present a method based on this assumption to quickly determine shadows cast by leaves onto other leaves. To this end, we simulate the presence of these shadows rather than projecting them exactly. The characteristics of these simulated shadows (movement, parallax, size, softness, and color) evolve realistically when the lighting conditions change. Our method is fast and supports soft shadows.