Generation of a control stream for a tile

Patent metadata

Field	Value
Publication number	US-10140761-B2
Application number	US-201715499038-A
Country	US
Kind code	B2
Filing date	Apr 27, 2017
Priority date	Apr 29, 2016
Publication date	Nov 27, 2018
Grant date	Nov 27, 2018

Abstract

A method of processing primitives within a tiling unit of a graphics processing system comprises determining whether a primitive falls within a tile based on positions of samples within each pixel. If it is determined that the primitive does fall within a tile based on the positions of samples within pixels in a tile, an association between the tile and the primitive is stored to indicate that the primitive is present in the tile. For example, an identifier for the primitive may be added to a control stream for the tile to indicate that the primitive is present in the tile. Various different methods are described to make the determination and these may be used separately or in any combination.

First claim

The invention claimed is:

1. A method of processing primitives within a tiling unit of a graphics processing system, the method comprising:
determining whether a primitive falls within a tile based on positions of samples within pixels in the tile, said determining comprising:
generating intersection points between edges of the primitive and boundaries of the tile;
forming a sub-polygon inside the tile by replacing vertices of the primitive outside the tile with the intersection points; and
determining whether the sub-polygon overlaps any of the sample positions within the tile, to thereby determine whether the primitive falls within the tile; and

in response to determining that a primitive does fall within a tile based on the positions of samples within pixels in the tile, storing an association between the tile and the primitive to indicate that the primitive is present in the tile.

2. The method according to claim 1 , wherein said storing an association between the tile and the primitive comprises adding an identifier for the primitive to a control stream for the tile.

3. The method according to claim 1 , wherein said storing an association between the tile and the primitive comprises adding an identifier for the tile to a tile list for the primitive.

4. The method according to claim 1 , further comprising rendering primitives in a tile using the stored associations, wherein the rendering is performed at each sample position within the tile.

5. The method according to claim 1 , wherein the determination is performed at a reduced sample precision.

6. the method according to claim 1 , wherein said determining whether the sub-polygon overlaps any of the sample positions within the tile comprises:
generating a bounding box of the sub-polygon; and
determining whether the primitive falls within the tile based on the bounding box of the sub-polygon.

7. The method according to claim 6 , wherein determining whether a primitive falls within a tile based the bounding box of the sub-polygon comprises:
determining if the bounding box of the sub-polygon overlaps any samples in the tile; and
in response to determining that the bounding box of the sub-polygon overlaps any samples in the tile, determining that the primitive falls within the tile.

8. The method according to claim 7 , wherein generating intersection points between edges of the primitive and boundaries of the tile comprises:
generating a bounding box of the tile at sample precision; and
generating intersection points between edges of the primitive and edges of the bounding box of the tile at sample precision.

9. The method according to claim 7 , wherein forming a sub-polygon inside the tile by replacing vertices of the primitive outside the tile with the intersection points comprises:
forming an initial sub-polygon inside the tile by replacing vertices of the primitive outside the tile with the intersection points; and
if the initial sub-polygon has more than three vertices, dividing the initial sub-polygon into a plurality of smaller sub-polygons, each having only three vertices,
and wherein a bounding box is generated at sample precision for each smaller sub-polygon and it is determined, for each generated bounding box, if it overlaps any samples in the tile.

10. The method according to claim 7 , wherein determining if the bounding box of the sub-polygon overlaps any samples in the tile comprises:
identifying four sampling locations in the tile using the bounding box of the sub-polygon; and
determining if the bounding box of the sub-polygon misses all four sampling locations in the tile.

11. The method according to claim 6 , wherein determining whether a primitive falls within a tile based on the bounding box of the sub-polygon comprises:
testing each edge of the sub-polygon which is also part of an edge of the primitive against each sample point in the bounding box of the sub-polygon to determine if any sample point is inside the sub-polygon; and
in response to determining that any sample point is inside the sub-polygon, determining that the primitive falls within the tile.

12. The method according to claim 11 , wherein generating intersection points between edges of the primitive and boundaries of the tile comprises:
generating a bounding box of the tile at sample precision; and
generating any intersection points between edges of the primitive and edges of the bounding box of the tile at sample precision.

13. The method according to claim 11 , wherein forming a sub-polygon inside the tile by replacing vertices of the primitive outside the tile with the intersection points comprises:
forming an initial sub-polygon inside the tile by replacing vertices of the primitive outside the tile with the intersection points; and
if the initial sub-polygon has more than three vertices, dividing the initial sub-polygon into a plurality of smaller sub-polygons, each having only three vertices,
and wherein a bounding box is generated at sample precision for each smaller sub-polygon and wherein testing each edge of the sub-polygon which is also part of an edge of the primitive against each sample point in the bounding box of the sub-polygon to determine if any sample point is inside the sub-polygon comprises:
for each smaller sub-polygon, testing each edge of the smaller sub-polygon which is also part of an edge of the primitive against each sample point in the bounding box of the smaller sub-polygon to determine if any sample point is inside the smaller sub-polygon.

14. The method according to claim 11 , wherein testing each edge of the sub-polygon which is also part of an edge of the primitive against each sample point in the bounding box of the sub-polygon to determine if any sample point is inside the sub-polygon comprises:
computing edge parameters for each edge of the sub-polygon which is also part of an edge of the primitive; and
testing each sample point in the bounding box of the sub-polygon against each edge.

15. The method according to claim 1 , wherein determining whether a primitive falls within a tile based on positions of samples within pixels in a tile further comprises:
generating a bounding box of the tile at sample precision;
generating a bounding box of the primitive at sample precision;
determining if the bounding boxes overlap; and
in response to determining that the bounding boxes do not overlap, determining that the primitive does not fall within the tile.

16. The method according to claim 1 , wherein determining whether a primitive falls within a tile based on positions of samples within a pixel comprises:
determining how many vertices of the primitive fall within the tile;
in response to determining that two or more vertices fall within the tile, determining that the primitive falls within the tile;
in response to determining that less than two vertices fall within the tile, generating any intersection points between edges of the primitive and boundaries of the tile;
in response to generating more than two intersection points, determining that the primitive falls within the tile;
in response to generating exactly two intersection points for a primitive with only one vertex in the tile and where the intersection points are on different boundaries of the tile, determining that the primitive falls within the tile;
in response to generating exactly two intersection points for a primitive with no vertices in the tile and where the intersection points are on the same boundary of the tile or on different boundaries of the tile that do not cross within the primitive, determining that the p

Assignees

• Imagination Tech Ltd

Inventors

• Yang Xile
• Belli Lorenzo
• Broadhurst Richard

Classifications

• G06T2210/21

  Collision detection, intersection · CPC title

• G06T17/20 Primary

  Finite element generation, e.g. wire-frame surface description, {tesselation} · CPC title

• G06T2210/12

  Bounding box · CPC title

• G06T17/10

  Constructive solid geometry [CSG] using solid primitives, e.g. cylinders, cubes · CPC title

• G06T15/005

  General purpose rendering architectures · CPC title