US 2006/0214931 A1 · Local, deformable precomputed radiance transfer

Abstract

Computer graphics image rendering techniques render images using a precomputed radiance transfer (PRT) to model local effects such as bumps, wrinkles, or other detailed features on an arbitrarily deformable model's surface. The techniques apply zonal harmonics (ZH) which approximate spherical functions as sums of circularly symmetric functions around different axes. By spatially varying both the axes and coefficients of these basis functions, approximations can fit to spatially varying transfer signals. Compared to the spherical harmonic (SH) basis, the ZH basis yields a more compact approximation, and can be rotated at a low computational expense suitable for dense per-vertex or per-pixel evaluation. This allows PRT to be mapped onto deforming models which re-orient the local coordinate frame.

Claims20

Dependent claims

A computer graphics image rendering method, comprising:

calculating data of radiance transfer for a plurality of points over a surface of a modeled object for a rest coordinate frame, where the radiance transfer data is represented as a function of at least a sum of one or more products of coefficients and circularly symmetric basis functions;
based on the radiance transfer data, evaluating radiance transfer over at least a portion of the surface of the modeled object from a lighting environment for a view direction;
and
producing an image of the modeled object as lit according to the radiance transfer evaluation.

1 more element

At least one data carrying medium having encoded thereon a software program executable on an image rendering system for a method of rendering graphics images of a modeled object based on data of local, deformable precomputed radiance transfer for sampled locations over a surface of the modeled object, the method comprising:

for a plurality of locations on the modeled object:
computing a rotation from a rest coordinate frame of the precomputed radiance transfer data to a deformed frame for the respective location;
applying the rotation to the precomputed radiance transfer data of the respective location;
based on the rotated radiance transfer data of the respective location, evaluating radiance transfer from a lighting environment for a view direction to yield a shading result for the respective location;
and
producing an image of the modeled object with the locations on the modeled object shaded according to their respective shading result.

3 more elements

A graphics image rendering system for rendering images of a deformable modeled object, comprising:

a lighting simulator operating to perform a lighting simulation of the modeled object to produce a set of radiance transfer matrices for a set of sampled locations over a surface of the modeled object representing radiance response including local effects to incident lighting at the respective sampled locations, where the radiance transfer matrices contain a set of coefficients for a representation of the radiance response at the respective sampled location as a sum of products of the coefficients multiplied by circularly symmetric basis functions;
a run-time image rendering engine operating to determine lighting from a lighting environment for each of a plurality of viewed locations on the modeled object in an image as a function of incident lighting from the lighting environment, the set of radiance transfer matrices, and rotations for the viewed locations from a rest coordinate frame to a deformed frame on the modeled object in a deformed position;
and
a display driver operating to present the image of the modeled object in the lighting environment with the determined lighting on a display.

1 more element

Dependencies are inferred from the claim text.

Local, deformable precomputed radiance transfer

Life of this patent

Local, deformable precomputed radiance transfer

Life of this patent

Abstract

Claims20