Patent ID: 7425957

Claim:
In a computer graphics system comprising at least a digital computing element and a display element operable to communicate with the computing element and to display a human-perceptible image in response to display-controlling electrical signals generated by the computing element, the image comprising a plurality of pixels, respective pixels having respective pixel values corresponding thereto, the display-controlling electrical signals being generated by the computing element based on pixel values generated by the computing element, the computing element being operable to generate a respective pixel value for respective pixels in the image, the pixel value for a given pixel being representative of a point in a scene as recorded on an image plane of a simulated camera, and the computing element comprising a sample point generator configured to generate a set of sample points, the improvement comprising: configuring the sample point generator to generate at least one sample point using at least one dependent sample, the at least one dependent sample comprising at least one element of a low-discrepancy sequence offset by at least one element of another low-discrepancy sequence, and providing, in the computing element, a function evaluator configured to generate at least one value representing an evaluation of a selected function at one of the sample points generated by said sample point generator, the value generated by the function evaluator corresponding to the pixel value, the pixel value being usable by the computing element to generate the display-controlling electrical signals to enable display of a human-perceptible image in response to the display-controlling electrical signals, and wherein the computing element is configured to generate a pixel value for a pixel using a selected ray-tracing methodology in which simulated rays are shot from respective ones of a plurality of subpixels in the pixel, each subpixel having coordinates (s x , s y ) in an image plane, the sample point generator being configured to map subpixel coordinates (s x , s y ) onto strata coordinates (j, k):=(s x mod 2 n , s y mod 2 n ), from which a ray is to be shot in accordance with x i = ( s x + σ ⁡ ( k ) 2 n , s y + σ ⁡ ( j ) 2 n ) where “i” is an instance number for the ray generated as i=j 2 n +σ(k) where integer permutation σ( k ):=2 n Φ b (k) for 0≦k<2 n for selected “n,” where Φ b (x) is a radical inverse function given by Φ b : N 0 -> I x = ∑ j = 0 ∞ ⁢ ⁢ a j ⁡ ( x ) ⁢ b j ↦ ∑ j = 0 ∞ ⁢ a j ⁡ ( x ) ⁢ b - j - 1 where (α j ) j=0 ∞ is the representation of “x” in a selected integer base “b.”