Z-texturing

• US 6,664,958 B1
• Filed: 11/28/2000
• Issued: 12/16/2003
• Est. Priority Date: 08/23/2000
• Status: Active Grant

• Current Assignee: Nintendo Company Limited
• Original Assignee: Nintendo Company Limited
• Inventors: Cheng, Howard, Moore, Robert, Leather, Mark M., Law, Patrick Y., Drebin, Robert A., DeLaurier, Anthony P.
• Primary Examiner(s): Zimmerman, Mark
• Assistant Examiner(s): Nguyen, Kimbinh T.
• Application Number:
  US09/722,378
• Time in Patent Office: 1,113 Days
• Field of Search: 345/419, 345/581, 345/582, 345/421, 345/422, 345/587, 345/506, 345/589, 345/606, 345/427, 345/428, 345/552
• US Class Current: 345/422
• CPC Class Codes: G06T 15/04 Texture mapping
• CPC Class Codes: G06T 15/40 Hidden part removal

Abstract

A graphics system including a custom graphics and audio processor produces exciting 2D and 3D graphics and surround sound. The system includes a graphics and audio processor including a 3D graphics pipeline and an audio digital signal processor. The same texture mapping hardware used for color texturing provides resampled z texturing for sprites with depth or other applications. A z blender performs a z blending operation in screen space to blend surface z values with z texel values to provide per-pixel mapping of resampled z textures onto sampled 3D surface locations. Z texels can represent absolute depths or depth displacements relative to primitive surface depth. The z texel values may add to or replace primitive surface z values, and a constant bias may be added if desired. The resulting depth values are used for occlusion testing. Z textures can be generated by copying out portions of an embedded z buffer and providing the copied depth values to the texture mapping hardware. Multiple z texel formats are supported.

Claims

1. A method of producing a 3D image comprising:

(a) applying texture coordinates to a texture mapper;

(b) using the texture mapper to resample a stored z texture map based on the texture coordinates;

(c) performing a depth blending in screen or eye space based at least in part on the accessed stored z texture map to specify data for depth buffering; and

(d) rendering an image based at least in pan on the depth buffered data.

2. The method of claim 1 wherein the performing step comprises replacing per pixel depth values with z texel absolute depth values.

3. The method of claim 1 wherein the performing step comprises using the accessed stored z texture map values as displacements to offset per pixel primitive z values.

4. The method of claim 1 wherein the stored z texture map comprises z texels having any one of plural z texel formats compatible with corresponding color texel formats.

5. The method of claim 1 further including rendering the z texture map into a depth buffer, and then copying the rendered z texture map from the depth buffer to the texture mapper.

6. The method of claim 1 further including using z texel values to selectively offset or replace rasterized z values corresponding to a surface.

7. The method of claim 1 wherein the texture mapper performs color and z texture mapping in different passes using common multipass texture mapping hardware.

9. The method of claim 1 wherein the depth blending performing step uses said z texture to remove hidden surfaces.

8. A method of producing a 3D image comprising:

(a) applying texture coordinates to a texture mapper;

(b) using the texture mapper to resample a stored z texture map based on the texture coordinates;

(c) performing a depth blending in screen or eye space based at least in part on the accessed stored z texture map to specify data for depth buffering;

(d) rendering an image based at least in part on the depth buffered data; and

(e) further including adding a bias value to a screen space blend of z texel values and rasterized surface z values.

10. A z blender comprising:

a first input adapted to receive at least one rasterized depth value corresponding to a pixel;

a second input adapted to receive at least one z texel value;

blend logic coupled to the first and second inputs, said blend logic blending the first input with the second input to provide a z blend for said pixel; and

further blend logic that adds a bias value to the z blend and provides at least one depth value for use in a hidden surface removal operation.

11. In a graphics pipeline including a texture mapper and an embedded z buffer, a method of performing z texturing comprising:

copying out at least a part of the embedded z buffer into a texture memory associated with the texture mapper; and

performing a z texture mapping operation based on the copied z texture.

12. A graphics chip including:

a graphics pipeline including a texture unit having an embedded texture memory, and

an embedded frame buffer including a color frame buffer and a z buffer,

wherein said embedded texture memory is configurable to store the z textures in any of a plurality of different formats.

14. The apparatus of claim 12 wherein said embedded texture memory stores z texels in formats compatible with color texels, and is shared between color texturing and z texturing.

15. The apparatus of claim 12 further including a z blender tat blends z texel values with primitive surface z values by performing at least one depth blending operation in screen space.

13. A graphics chip including:

a graphics pipeline including a texture unit having an embedded texture memory, and

an embedded frame buffer including a color frame buffer and a z buffer,

wherein said embedded texture memory is configurable to store the z textures in any of a plurality of different formats,

wherein said embedded texture memory is configurable to store z texels in any of unsigned 8-bit, unsigned 16-bit or unsigned 24-bit formats.

16. In a graphics pipeline, a multi-stage texture environment pixel shader comprising:

a plurality of input selectors;

a texture environment operator coupled to the plurality of input selectors;

at least one intermediate value storage register; and

a z blender adapted to blend, in at least one stage, resampled z texel values with per-pixel primitive surface z values to provide blended z values for occlusion testing.

17. The graphics pipeline of claim 16 wherein the z blender blends within a last pixel shader stage.