Frustum rendering in computer graphics

1. A graphics processing system comprising:

a tiling unit configured to tile a first view of a scene into a plurality of tiles;

a processing unit configured to identify a first subset of the tiles that are associated with regions of the scene that are viewable in a second view; and

a rendering unit configured to render to a shadow map texture each of the identified tiles.

2. A system as claimed in claim 1 , wherein:

the regions of the scene that are viewable in the second view is a view frustum of the second view; and

the first subset of tiles are identified in dependence on determining the position of the view frustum of the second view from the first view.

3. A system as claimed in claim 1 , wherein the first subset of tiles are identified in dependence on a frustum model comprising primitives representing a view frustum of the second view.

4. A system as claimed in claim 3 , wherein:

the tiling unit is configured to tile the frustum model from the first view into the plurality of tiles and generate a list of frustum primitives associated with each of the tiles; and

the processing unit is configured to identify the first subset of tiles in dependence on the list of frustum primitives, each of the first subset of tiles being associated with at least a predetermined number of frustum primitives.

5. A system as claimed in claim 1 , wherein the processing unit is configured to identify a second subset of tiles of the first view that are associated with at least one object in the scene, the rendering unit being configured to render each of the tiles that are identified in both the first and second subset.

6. A system as claimed in claim 5 , wherein the tiling unit is configured to tile the at least one object in the scene from the first view into the plurality of tiles to generate a list of object primitives associated with each of the tiles, and wherein the processing unit is configured to identify the second subset of tiles in dependence on the list of object primitives for the first view, each of the second subset of tiles being associated with at least a predetermined number of object primitives.

7. A system as claimed in claim 1 , wherein the processing unit is configured to:

identify primitives that, from a point of view for the first view, are further than a view frustum for the second view; and

clip the identified primitives from the scene, wherein the first view is a view of the clipped scene.

8. A system as claimed in claim 1 , wherein the rendering unit is configured to apply the shadow map texture to the scene in a subsequent render of the scene.

9. A system as claimed in claim 8 , wherein the shadow map texture is applied to the second view of the scene, the second view being different to the first view.

10. A graphics processing method comprising:

tiling a first view of a scene into a plurality of tiles;

identifying a first subset of the tiles that are associated with regions of the scene that are viewable in a second view; and

rendering to a shadow map texture each of the identified tiles.

11. A method as claimed in claim 10 , wherein:

the regions of the scene that are viewable in the second view is a view frustum of the second view; and

the first subset of tiles are identified in dependence on determining the position of the view frustum of the second view from the first view.

12. A method as claimed in claim 10 , wherein the first subset of tiles are identified in dependence on a frustum model comprising primitives representing a view frustum of the second view.

13. A method as claimed in claim 12 , wherein:

tiling the first view comprises tiling the frustum model from the first view into the plurality of tiles, and generating a list of frustum primitives associated with each of the tiles; and

identifying the first subset comprises identifying the first subset of tiles in dependence on the list of frustum primitives, each of the first subset of tiles being associated with at least a predetermined number of frustum primitives.

14. A method as claimed in claim 10 , further comprising identifying a second subset of tiles of the first view that are associated with at least one object in the scene, wherein the rendering step comprises rendering tiles that are identified in both the first and second subset.

15. A method as claimed in claim 14 , wherein tiling the first view comprises tiling the at least one object in the scene from the first view into the plurality of tiles, and generating a list of object primitives associated with each of the tiles, and wherein the second subset of tiles are identified in dependence on the list of object primitives for the first view and each of the second subset of tiles are associated with at least a predetermined number of object primitives.

16. A method as claimed in claim 10 , further comprising:

identifying primitives that, from a point of view for the first view, are further than a view frustum for the second view; and

clipping the identified primitives from the scene, wherein the first view is a view of the clipped scene.

17. A method as claimed in claim 10 , wherein the method further comprises applying the shadow map texture to the scene in a subsequent render of the scene.

18. A method as claimed in claim 17 , wherein the texture is applied to the second view of the scene, the second view being different to the first view.

19. A non-transitory computer readable storage medium having stored thereon an integrated circuit definition dataset that, when processed in an integrated circuit manufacturing system, configures the manufacturing system to manufacture a graphics processing system comprising:

a tiling unit configured to tile a first view of a scene into a plurality of tiles;

a processing unit configured to identify a first subset of the tiles that are associated with regions of the scene that are viewable in a second view; and

a rendering unit configured to render to a shadow map texture each of the identified tiles.