Rendering stroked curves in graphics processing systems

摘要

When rendering a stroked curve for display in a graphics processing system, an input stroked curve 1 defined in user space 2 is received by the system. The portion of a canonical space 5 that corresponds to the received stroked curve 1 is determined by determining the portion of a canonical curve 12 defined in the canonical space 5 that corresponds to the received stroked curve 1. Then, for each of a plurality of sampling points within one or more primitives 4 that are generated to cover the received stroked curve 1′ following its projection into surface space 3, it is determined whether a corresponding location in canonical space 5 (to the sampling point in surface space 3) is within the portion of the canonical space that corresponds to the received stroked curve, e.g. by looking up suitable information that has been stored (in advance) in one or more graphics textures. Data for rendering the received stroked curve 1 (e.g. RGBA values) is then assigned to each of the plurality of sampling points based on the determination.

主权项

1. A method of rendering a stroked curve for display in a graphics processing system, the method comprising:
receiving an input stroked curve defined in a user space by a centre curve and an associated stroke width; determining a portion of a canonical space that corresponds to the received stroked curve; wherein the portion of the canonical space has a length defined by a portion of a canonical curve in the canonical space which corresponds to the received stroked curve, and a width defined by the associated stroke width multiplied by a scaling factor component of a transformation between the user space and the canonical space; projecting the received stroked curve using a received transformation into a surface space; defining at least one primitive that covers the projected stroked curve in the surface space; and for each of a plurality of sampling points within the at least one primitive:
mapping the sampling point to a corresponding location in the canonical space;determining whether the corresponding location is within the portion of the canonical space that corresponds to the received stroked curve; andassigning data for rendering the received stroked curve to the sampling point if the corresponding location is within the portion of the canonical space that corresponds to the received stroked curve;wherein said step of determining whether the corresponding location is within the portion of the canonical space that corresponds to the received stroked curve comprises determining whether the length of a line extending perpendicularly from the canonical curve to the corresponding location in the canonical space is less than or equal to half the associated stroke width multiplied by the scaling factor component.