Global illumination models for volume rendering

IEEE Transactions on Visualization and Computer Graphics, 1995

This tutorial survey paper reviews several different models for light interaction with volume densities of absorbing, glowing, reflecting, and/or scattering material. They are, in order of increasing realism, absorption only, emission only, emission and absorption combined, single scattering of external illumination without shadows, single scattering with shadows, and multiple scattering. For each model I give the physical assumptions, describe the applications for which it is appropriate, derive the differential or integral equations for light transport, present calculations methods for solving them, and show output images for a data set representing a cloud. Special attention is given to calculation methods for the multiple scattering model.

Computer Graphics Forum, 2013

Interactive volume rendering in its standard formulation has become an increasingly important tool in many application domains. In recent years several advanced volumetric illumination techniques to be used in interactive scenarios have been proposed. These techniques claim to have perceptual benefits as well as being capable of producing more realistic volume rendered images. Naturally, they cover a wide spectrum of illumination effects, including varying shading and scattering effects. In this survey, we review and classify the existing techniques for advanced volumetric illumination. The classification will be conducted based on their technical realization, their performance behavior as well as their perceptual capabilities. Based on the limitations revealed in this review, we will define future challenges in the area of interactive advanced volumetric illumination.

In this paper various algorithms for rendering gaseous phenomena are reviewed. In computer graphics such algorithms are used to model natural scenes containing clouds, fog, ames and so on. On the other hand displaying three dimensional scalar datasets as cloudy objects has become an important technique in scienti c visualization. Our emphasis is on this latter subject of so-called direct volume rendering. All algorithms will be discussed within the framework of linear transport theory. The equation of transfer is derived. This equation is suitable to describe the radiation eld in a participating medium where absorption, emission, and scattering of light can occur. Almost all volume rendering algorithms can beshown to solve special cases of the equation of transfer. Related problems like the mapping from data values to model parameters or possible parallelization strategies will be discussed as well.

1993

In this paper various algorithms for rendering gaseous phenomena are reviewed. In computer graphics such algorithms are used to model natural scenes containing clouds, fog, flames and so on. On the other hand displaying three dimensional scalar datasets as cloudy objects has become an important technique in scientific visualization. Our emphasis is on this latter subject of so-called direct volume rendering. All algorithms will be discussed within the framework of linear transport theory. The equation of transfer is derived. This equation is suitable to describe the radiation field in a participating medium where absorption, emission, and scattering of light can occur. Almost all volume rendering algorithms can be shown to solve special cases of the equation of transfer. Related problems like the mapping from data values to model parameters or possible parallelization strategies will be discussed as well.

IEEE Transactions on Visualization and Computer Graphics, 2003

In this paper we present an algorithm that accelerates 3D texturebased volume rendering of large and sparse data sets. A hierarchical data structure (known as AMR tree) consisting of nested uniform grids is employed in order to efficiently encode regions of interest. The hierarchies resulting from this kind of space partitioning yield a good balance between the amount of volume to render and the number of texture bricks -a prerequisite for fast rendering.

ACM Siggraph Computer Graphics, 1988

A technique for rendering images Of volumes containing mixtures of materials is presented. The shading model allows both the interior of a material and the boundary between materials to be colored. Image projection is performed by simulating the absorption of light along the ray path to the eye. The algorithms used are designed to avoid artifacts caused by aliasing and quantization and can be efficiently implemented on an image computer. Images from a variety of applications are shown.

1993

In this paper various algorithms for rendering gaseous phenomena are reviewed. In computer graphics such algorithms are used to model natural scenes containing clouds, fog, ames and so on. On the other hand displaying three dimensional scalar datasets as cloudy objects has become an important technique in scienti c visualization. Our emphasis is on this latter subject of so-called direct volume rendering. All algorithms will be discussed within the framework of linear transport theory. The equation of transfer is derived. This equation is suitable to describe the radiation eld in a participating medium where absorption, emission, and scattering of light can occur. Almost all volume rendering algorithms can beshown to solve special cases of the equation of transfer. Related problems like the mapping from data values to model parameters or possible parallelization strategies will be discussed as well.

Computer Graphics Forum, 2009

Volumetric rendering is widely used to examine 3D scalar fields from scanners and direct numerical simulation datasets. One key aspect of volumetric rendering is the ability to provide shading cues to aid in understanding structure contained in the datasets. 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, we propose a novel shading model for interactive direct volume rendering that provides perceptual cues similar to that 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. Our 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. Unlike ambient occlusion methods, modifications to the volume, such as clipping planes or changes to the transfer function, are incorporated into the resulting occlusion-based shading. Figure 1: From left to right: a) Visible male data set with occlusion of solid and transparent materials (3.4 FPS, 996 slices) b) CT scan of an engine block where a clipping plane was used to show the exhaust port (13.3 FPS, 679 slices) c) Bonsai data set of which complex features are exposed by our ambient occlusion approximation (4.

1993

Volume rendering is a title often ambiguously used in science. One meaning often quoted is:`to render any three volume dimensional data set'; however, within this categorisation \surface rendering" is contained. Surface rendering is a technique for visualising a geometric representation of a surface from a three dimensional volume data set. A more correct de nition of Volume Rendering would only incorporate the direct visualisation of volumes, without the use of intermediate surface geometry representations. Hence we state:`Volume Rendering is the Direct Visualisation of any three dimensional Volume data set; without the use of an intermediate geometric representation for isosurfaces';`Surface Rendering is the Visualisation of a surface, from a geometric approximation of an isosurface, within a Volume data set'; where an isosurface is a surface formed from a cross connection of data points, within a volume, of equal value or density. This paper is an overview of both Surface Rendering and Volume Rendering techniques. Surface Rendering mainly consists of contouring lines over data points and triangulations between contours. Volume rendering methods consist of ray casting techniques that allow the ray to be cast from the viewing plane into the object and the transparency, opacity and colour calculated for each cell; the rays are often cast until an opaque object is`hit' or the ray exits the volume.

2002

Abstract The work presented here describes two methods to incorporate viable illumination models into Fourier Volume Rendering (FVR). The lack of adequate illumination has been one of the impediments for the wide spread acceptance of FVR. Our first method adapts the Gamma Corrected Hemispherical Shading (GCHS) proposed by Scoggins et al.[11] for FVR. We achieve interactive rendering for constant diffusive light sources. Our second method operates on data transformed by spherical harmonic functions.