EFFICIENT RENDERING OF HETEROGENEOUS POLYDISPERSE GRANULAR MEDIA

Number: 20180144540
Published: 2018-05-24
Filed: 2017-02-08
Assignee: Disney Enterprises, Inc.
Inventors: NOVAK; Jan; MULLER; Thomas; PAPAS; Marios; JAROSZ; Wojciech
CPC: G06T15/08; G06T15/506; G06T15/10
Verdict: Medium Notable software
Source: Google Patents · FreePatentsOnline

The keeper's note

Granular-media rendering (graphics).

Abstract

The disclosure provides an approach for rendering heterogeneous polydisperse granular media. In one aspect, a rendering application renders such granular media using a combination of explicit path tracing and accelerated path construction using proxy path tracing, shell tracing, and volumetric path tracing. In proxy path tracing in particular, the rendering application instantiates proxy geometry in the form of a bounding sphere and determines internal scattering in the grain using a precomputed grain scattering distribution function that relates incident and outgoing radiance functions on the bounding sphere. In shell tracing, the rendering application uses shells to aggregate many grain interactions into a single step. The rendering application derives a continuous liquid/volume equivalent to the granular material based on the material's optical properties and selects a precomputed shell transport function (STF) to use from a database by interpolating nearby database entries using radiative transfer equation (RTE) parameters at the shell's center.

Background

BACKGROUNDField of the Invention

Aspects of the disclosure presented herein relate to computer rendering of three-dimensional (3D) virtual scenes. More specifically, this disclosure presents techniques for rendering heterogeneous polydisperse granular media.Description of the Related Art

Discrete granular materials frequently found in natural scenes include wet and dry sand, bubbles and foam in liquids, layers of soils, snow, a bowl with spices, and the like. Such granular materials can be made up of massive, dynamic, and heterogeneous collections of discrete grains with different sizes (i.e., polydisperse). Granular materials are characterized by both fine-scale details of individual grains as well as smooth large-scale appearances, which result from the material's properties and the arrangement of individual grains in the material.

The fine-scale details in granular materials result from high-frequency low-order transport of light rays through individual grains, and the high-frequency visual structures for individual grains include geometric detail, sudden changes in color, and glints that typically arise from the first few interactions of the light upon hitting the granular assembly. Characteristics of such high-frequency low-order transport through individual grains are difficult to approximate with an aggregate approximation without eliminating salient details. On the other hand, granular materials may also have smooth large-scale appearances resulting

Claims

1. A computer-implemented method for rendering a granular medium, comprising: computing a plurality of shell transport functions (STFs) over an appearance space of optical parameters, wherein each STF aggregates a plurality of grain interactions into a single step; receiving geometry of a scene which includes the granular medium; determining a continuous volume approximation of the granular medium, the continuous volume approximation having optical properties of the granular medium; tracing light paths from a camera into the scene; and for each of a plurality of traced light paths that intersect the granular medium: successively selecting one or more STFs associated with shells which fit in the granular medium based on the optical properties of the continuous volume approximation corresponding to the shells associated with the STFs, and constructing the traced light path using the selected STFs; and generating at least a rendered image of the scene based on the traced light paths. 13. A non-transitory computer-readable storage medium storing a program, which, when executed by a processor performs operations for rendering a granular medium, the operations comprising: computing a plurality of shell transport functions (STFs) over an appearance space of optical parameters, wherein each STF aggregates a plurality of grain interactions into a single step; receiving geometry of a scene which includes the granular medium; determining a continuous volume approximation of the granular medium, the continuous volume approximation having optical properties of the granular medium; tracing light paths from a camera into the scene; and for each of a plurality of traced light paths that intersect the granular medium: successively selecting one or more STFs associated with shells which fit in the granular medium based on the optical properties of the continuous volume approximation corresponding to the shells associated with the STFs, and constructing the traced light path using the selected STFs; and generating at least a rendered image of the scene based on the traced light paths. 21. A system, comprising: a processor; and a memory, wherein the memory includes a program configured to perform operations for rendering a granular medium, the operations comprising: computing a plurality of shell transport functions (STFs) over an appearance space of optical parameters, wherein each STF aggregates a plurality of grain interactions into a single step, receiving geometry of a scene which includes the granular medium, determining a continuous volume approximation of the granular medium, the continuous volume approximation having optical properties of the granular medium, tracing light paths from a camera into the scene, and for each of a plurality of traced light paths that intersect the granular medium: successively selecting one or more STFs associated with shells which fit in the granular medium based on the optical properties of the continuous volume approximation corresponding to the shells associated with the STFs; and constructing the traced light path using the selected STFs, and generating at least a rendered image of the scene based on the traced light paths.