US 9,959,669 B2Granted

Method and apparatus for rendering a computer generated image

AssigneeImagination Technology Limited

InventorSimon Fenney

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Abstract

A method and apparatus for rendering a computer-generated image using a stencil buffer is described. The method divides an arbitrary closed polygonal contour into first and higher level primitives, where first level primitives correspond to contiguous vertices in the arbitrary closed polygonal contour and higher level primitives correspond to the end vertices of consecutive primitives of the immediately preceding primitive level. The method reduces the level of overdraw when rendering the arbitrary polygonal contour using a stencil buffer compared to other image space methods. A method of producing the primitives in an interleaved order, with second and higher level primitives being produced before the final first level primitives of the contour, is described which improves cache hit rate by reusing more vertices between primitives as they are produced.

Claims8

Dependent claims

A method for rendering a computer generated image using a stencil buffer, comprising:

receiving an arbitrary closed polygonal contour, the contour having N vertices;
dividing the arbitrary closed polygonal contour into primitives, each primitive being a polygon having at least 3 and at most P vertices where 2<P<N;
setting up a stencil buffer by using primitives that have a winding order consistent with an overall winding order of the arbitrary closed polygonal contour and primitives that have a winding order inconsistent with the overall winding order of the arbitrary closed polygonal contour;
and
using the stencil buffer to render the primitives to produce a computer generated image by comparing the winding order of each primitive used to setup the stencil buffer to the overall winding order of the arbitrary closed polygonal contour and performing one or more of color and texturing processes, only within areas of an image that are covered by primitives whose winding order is the same as the overall winding order and avoiding performing the one or more of color and texturing processes for areas of the image that are within the primitives that have a winding order inconsistent with the overall winding order of the arbitrary closed polygonal contour.

2 more elements

An apparatus for rendering a computer generated image comprising:

an input for receiving an N-vertex arbitrary closed polygonal contour;
a state machine control for controlling dividing of the arbitrary N-vertex closed polygonal contour into primitives, each primitive being a polygon having at least 3 and at most P vertices where 2<P<N, and outputting the primitives;
and
a stencil buffer configured to be set up using primitives that have a winding order consistent with the overall winding order of the arbitrary closed polygonal contour and primitives that have a winding order inconsistent with the overall winding order of the arbitrary closed polygonal contour and to render to render the primitives to produce a computer generated image by comparing the winding order of each primitive to the overall winding order of the arbitrary closed polygonal contour and using, in one or more of color and texturing processes, only those primitives whose winding order is the same as the overall winding order.

1 more element

Dependencies are inferred from the claim text.

Facts

Application: 13/720,318Filed 19 Dec 2012 · division
Priority: GB 0908506.918 May 2009
Published: US 2013/0106854 A12 May 2013
Granted: 1 May 2018
Term ends: Not estimatedThe source records don’t support an estimate.

Classification4 codes

G06T 17/20
Three-dimensional [3D] modelling for computer graphics: finite element generation, e.g. wire-frame surface description, tesselation
G06T 9/00
Image coding
G06T 15/005
Three-dimensional [3D] image rendering: general purpose rendering architectures
G06T
Image data processing or generation, in general

Family

Application12/800,540Parent of this division · filed 17 May 2010
US 2013/0106854 A1Pre-grant publication · published 2 May 2013
US 8,654,146 B2Parent of this division
US 2010/0289809 A1Published application
US 9,959,669 B2This patent

From the US filing history. Foreign family members aren’t listed.