Abstract: A graphics processing pipeline includes a fragment shader 8 and can carry out blending either by means of a blend shading software routine in a blend shader 10, or by using fixed function, dedicated processing hardware blending units 12. When the programmable blend shading path using the blend shader 10 is selected, the blend shader 10 is configured to provide the alpha value 110 generated by the fragment shading operation as an output to the multisample coverage operations unit 105 and the alpha test unit 106 of the fixed function hardware unit pipeline. This allows the alpha test on the alpha values generated by the fragment shader 8 still to be performed using the multisample coverage operations hardware unit 105 and the alpha test hardware unit 106, instead of having to emulate those operations in the blend shading software routine in the blend shader 10.

Abstract: A method of rendering a stroked curve for display in a graphics processing system in which an input stroked curve 2 to be displayed, such as a character in a computer font or a portion thereof, is defined in user space 4 and projected into a surface space 6 for display. For each of one or more sampling points in the surface space 6, a corresponding sampling position in a projected space 12 is determined, and predetermined information is used to estimate the extent in a defined direction of a projected form of the stroked curve in the projected space 12 at a position along the length of the projected form of the stroked curve corresponding to the position along the length of the projected form of the stroked curve of the sampling position in the projected space 12. The estimated extent is then used to determine whether the sampling position in question falls within the stroked curve or not, thereby allowing suitable rendering data to be assigned to the sampling point.

Abstract: A graphics processing pipeline includes a fragment shader 8 and can carry out blending either by means of a blend shading software routine in a blend shader 10, or by using fixed function, dedicated processing hardware blending units 12. When the programmable blend shading path using the blend shader 10 is selected, the blend shader 10 is configured to provide the alpha value 110 generated by the fragment shading operation as an output to the multisample coverage operations unit 105 and the alpha test unit 106 of the fixed function hardware unit pipeline. This allows the alpha test on the alpha values generated by the fragment shader 8 still to be performed using the multisample coverage operations hardware unit 105 and the alpha test hardware unit 106, instead of having to emulate those operations in the blend shading software routine in the blend shader 10.

Abstract: A method of rendering a stroked curve for display in a graphics processing system in which an input stroked curve 2 to be displayed, such as a character in a computer font or a portion thereof, is defined in user space 4 and projected into a surface space 6 for display. For each of one or more sampling points in the surface space 6, a corresponding sampling position in a projected space 12 is determined, and predetermined information is used to estimate the extent in a defined direction of a projected form of the stroked curve in the projected space 12 at a position along the length of the projected form of the stroked curve corresponding to the position along the length of the projected form of the stroked curve of the sampling position in the projected space 12. The estimated extent is then used to determine whether the sampling position in question falls within the stroked curve or not, thereby allowing suitable rendering data to be assigned to the sampling point.