Exposure Render: An Interactive Photo-Realistic Volume Rendering Framework

Abstract

The field of volume visualization has undergone rapid development during the past years, both due to advances in suitable computing hardware and due to the increasing availability of large volume datasets. Recent work has focused on increasing the visual realism in Direct Volume Rendering (DVR) by integrating a number of visually plausible but often effect-specific rendering techniques, for instance modeling of light occlusion and depth of field. Besides yielding more attractive renderings, especially the more realistic lighting has a positive effect on perceptual tasks. Although these new rendering techniques yield impressive results, they exhibit limitations in terms of their exibility and their performance. Monte Carlo ray tracing (MCRT), coupled with physically based light transport, is the de-facto standard for synthesizing highly realistic images in the graphics domain, although usually not from volumetric data. Due to the stochastic sampling of MCRT algorithms, numerous effects can be achieved in a relatively straight-forward fashion. For this reason, we have developed a practical framework that applies MCRT techniques also to direct volume rendering (DVR). With this work, we demonstrate that a host of realistic effects, including physically based lighting, can be simulated in a generic and flexible fashion, leading to interactive DVR with improved realism. In the hope that this improved approach to DVR will see more use in practice, we have made available our framework under a permissive open source license.

Correlated Photon Mapping for Interactive Global Illumination of Time-Varying Volumetric Data

“…High quality interactive volumetric illumination methods that have few or no limitations on the illumination complexity are too slow to interactively explore time-varying volumetric data [21]. A comprehensive overview of interactive global illumination techniques can be found in surveys within the topic [16,31].…”

“…Monte Carlo ray-tracing has been proposed as another alternative for volumetric illumination [34,21]. Unfortunately, the Monte Carlo ray-tracing based methods come with the computational penalty that require progressive computation to stay interactive if a noise-free rendering is desired.…”

Lighting Design for Globally Illuminated Volume Rendering

“…In [20] light propagation is simulated in the volume-space for shadow and single scattering. Kroes et al [10] applied Monte Carlo ray tracing to the DVR which can achieve various global illumination effects including shadow and single scattering. However, it still takes several seconds to converge which affects the interactivity and the rendering results are blurred due to the strong noise filtering.…”

Enhancing Salient Features in Volumetric Data Using Illumination and Transfer Functions

“…Techniques used for offline computation are able to produce high quality illumination and have less restrictions on the type of illumination effects that can be achieved. Kroes et al [36] presented a framework adapted to use the GPU for path-tracing of volume data. They are able to produce high quality direct illumination at the expense of slow frame-rates, i.e.…”

“…This has allowed them to take advantage of different aspects of the volume rendering equation under the assumption that the data is not changing. For example, high quality illumination can be achieved by applying iterative techniques that improve the quality over time [36]. However, this is not possible for time-varying data as the scene is constantly changing and therefore resets the computation each frame.…”