High performance shading of large volumetric data using screen-space partial derivatives
First Claim
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1. A shading method for rendering volumetric data having a plurality of pixels, each of the plurality of pixels having a scalar value, comprising:
- determining a partial derivative with respect to the x direction of a first of the plurality of pixels in a screen-space;
determining a partial derivative with respect to the y direction of the first of the plurality of pixels in the screen-space;
determining a partial derivative with respect to the z direction of the first of the plurality of pixels in an object-space; and
determining a gradient based on the partial derivative with respect to the x direction, based on the partial derivative with respect to the y direction and based on the partial derivative with respect to the z direction.
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Abstract
A method and system for shading large volumetric data sets using partial derivatives computed in screen-space. The method and system provide a fast and efficient shading a large datasets. Screen space derivatives are computed efficiently by evaluating neighboring pixel information together. The method can be efficiently implemented using GPUs (graphics processing units) that provides some access to information about neighboring pixels using ddx and ddy fragment processing functions.
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Citations
23 Claims
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1. A shading method for rendering volumetric data having a plurality of pixels, each of the plurality of pixels having a scalar value, comprising:
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determining a partial derivative with respect to the x direction of a first of the plurality of pixels in a screen-space;
determining a partial derivative with respect to the y direction of the first of the plurality of pixels in the screen-space;
determining a partial derivative with respect to the z direction of the first of the plurality of pixels in an object-space; and
determining a gradient based on the partial derivative with respect to the x direction, based on the partial derivative with respect to the y direction and based on the partial derivative with respect to the z direction. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A system of shading for rendering volumetric data, comprising:
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a device for imaging a body part to derive scalar values associated with a plurality of pixels;
a processor that, for each of the plurality of pixels, determines a partial derivative in an x direction in a screen-space, determines a partial derivative in a y direction and determines a gradient based in part on the partial derivative in the x direction and on the partial derivative in the y direction;
wherein the processor renders volumetric data based in part on the gradient; and
a display that displays the rendered volumetric data. - View Dependent Claims (13, 15, 16, 17, 18)
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14. The system as claimed in claim 14, wherein the graphics processing unit uses a fragment function ddx and a fragment function ddy.
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19. A method of rendering volumetric data having a plurality of pixels, comprising:
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obtaining a sample of data from a volume;
classifying the sample;
computing a gradient for each of the plurality of pixels, the gradient being based at least in part on data in screen-space;
normalizing the gradient;
computing diffuse and specular components; and
computing output colors. - View Dependent Claims (20, 21)
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22. A shading method for rendering volumetric data, the method comprising:
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selecting a first pixel in screen-space coordinates, the first pixel having a corresponding scalar value obtained from the volumetric data;
determining a difference between the scalar value associated with the first pixel and a scalar value associated with a neighboring pixel in a x direction in screen space;
determining a difference between the scalar value associated with the first pixel and a scalar value associated with a neighboring pixel in a y direction in screen space;
determining a gradient associated with the first pixel based on the differences; and
using the gradient to compute a shading characteristic of the first pixel. - View Dependent Claims (23)
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Specification