Ray tracing across refractive boundaries

Number: 9916677
Published: 2018-03-13
Filed: 2016-07-26
Assignee: Disney Enterprises, Inc.
Inventors: Novak; Jan; Koerner; David; Jarosz; Wojciech; Kutz; Peter; Habel; Ralf
CPC: G06T15/50; G06T7/13; G06T1/20; G06T15/06
Verdict: Medium Notable software
Source: Google Patents · FreePatentsOnline

The keeper's note

Ray tracing across refractive boundaries (rendering).

Abstract

According to one exemplary implementation, a method for use by a global illumination system including a hardware processor includes identifying, using the hardware processor, a first interior vertex of multiple first interior vertices of a light path, the first interior vertices being situated within a volume having a refractive boundary. In addition, the method includes determining, using the hardware processor, a surface vertex of the light path at the refractive boundary, and determining, using the hardware processor, a linear direction from the surface vertex to a light source of the light path. The method also includes determining, using the hardware processor, one or more second interior vertices for completing the light path by constructing a path from the surface vertex to the first interior vertex, based on the linear direction, the surface vertex and the first interior vertex.

Background

BACKGROUND(1) Next-Event Estimation or “NEE” is a widely used conventional approach to performing ray tracing in the absence of refraction. NEE estimates direct illumination by sampling a light source and testing its visibility by casting a shadow ray. NEE may be performed at each step of light path construction, i.e., at every vertex of a light path, for example.(2) However, despite its usefulness for estimating direct illumination, NEE is unable to provide accurate estimates for illumination resulting from subsurface scattering of light within a volume enclosed by a refractive boundary. Examples of such volumes include marble statuary, human tissue, milk, and other translucent media. Because NEE connects the light path vertices within a volume enclosed by a refractive boundary with a light source external to the enclosed volume using straight lines through the refractive boundary, the shadow rays utilized by NEE violate Snell's law when crossing the refractive boundary. Thus, a solution enabling ray tracing across refractive boundaries is desirable in order to enhance the accuracy with which illumination caused by subsurface light scattering in translucent media is rendered.SUMMARY(3) There are provided systems and methods for performing ray tracing across refractive boundaries, substantially as shown in and/or described in connection with at least one of the figures, and as set forth more completely in the claims.

Claims

1. A method for use by a global illumination system including a hardware processor and a display, the method comprising: identifying, using the hardware processor, a first interior vertex of a plurality of first interior vertices of a light path, the plurality of first interior vertices being situated within a volume having a refractive boundary; determining, using the hardware processor, a surface vertex of the light path at the refractive boundary; determining, using the hardware processor, a linear direction from the surface vertex to a light source of the light path; determining, using the hardware processor, one or more second interior vertices for completing the light path by constructing a path from the surface vertex to the first interior vertex, based on the linear direction, the surface vertex and the first interior vertex; and rendering, using the hardware processor, a scene on the display based on the one or more second interior vertices. 8. A method for use by a global illumination system including a hardware processor and a display, the method comprising: identifying, using the hardware processor, a first interior vertex of a plurality of first interior vertices of a light path, the plurality of first interior vertices being situated within a volume having a refractive boundary and including a medium having an anisotropic phase function; determining, using the hardware processor, a surface vertex of the light path at the refractive boundary; determining, using the hardware processor, one or more second interior vertices for completing the light path by constructing a path from the first interior vertex to the surface vertex, based on the anisotropic phase function, the surface vertex and the first interior vertex: and rendering, using the hardware processor, a scene on the display based on the one or more second interior vertices. 15. A method for use by a global illumination system including a hardware processor and a display, the method comprising: identifying, using the hardware processor, a plurality of first interior vertices and a second interior vertex of a light path, the plurality of first interior vertices and the second interior vertex being situated within a volume having a refractive boundary; determining, using the hardware processor, a surface vertex of the light path at the refractive boundary; relocating, using the hardware processor, the second interior vertex within the volume for completing the light path between the plurality of first interior vertices and the surface vertex: and rendering, using the hardware processor, a scene on the display based on the relocated second interior vertex within the volume.