Cylindrical wrapping using shader hardware

• US 7,663,621 B1
• Filed: 11/03/2006
• Issued: 02/16/2010
• Est. Priority Date: 11/03/2006
• Status: Active Grant

• Current Assignee: NVIDIA Corporation
• Original Assignee: NVIDIA Corporation
• Inventors: Ohannessian, Robert Jr., Allen, Roger L., Zable, Harold Robert
• Primary Examiner(s): Chauhan; Ulka
• Assistant Examiner(s): PRENDERGAST, ROBERTA D
• Application Number:
  US11/556,515
• Time in Patent Office: 1,201 Days
• Field of Search: 345/419, 345/426, 345/501, 345/505, 345/519, 345/582, 345/585
• US Class Current: 345/419
• CPC Class Codes: G06T 15/04 Texture mapping

Abstract

Circuits, methods, and apparatus that perform cylindrical wrapping in software without the need for a dedicated hardware circuit. One example performs cylindrical wrapping in software running on shader hardware. In one specific example, the shader hardware is a unified shader that alternately processes geometry, vertex, and fragment information. This unified shader is formed using a number of single-instruction, multiple-data units. Another example provides a method of performing a cylindrical wrap that ensures that a correct texture portion is used for a triangle that is divided by a “seam” of the wrap. To achieve this, primitive vertices are sorted such that results are vertex order invariant. One vertex is selected as a reference. For the other vertices, a difference is found for each coordinate and a corresponding coordinate of the reference vertex. If the coordinates are near, no change is made. If the coordinates are distant, the coordinate is adjusted.

Claims

1. A method of processing graphics information comprising:

receiving information regarding a plurality of primitives defining an object;

receiving information regarding a texture;

receiving an instruction to cylindrically wrap the object with the texture;

executing the instruction to cylindrically wrap the object with the texture using a geometry shader program running on shader hardware; and

storing the results in a memory,

wherein executing the instruction to cylindrically wrap the object with the texture using a geometry shader program running on shader hardware comprises;

selecting a first vertex from a plurality of vertices for a primitive in the plurality of primitives as a reference; and

for a second vertex of the primitive, for each coordinate of the second vertex;

determining whether a coordinate of the second vertex is more than a threshold distance away from a corresponding coordinate of the first vertex; and

if it is, then

modifying the coordinate of the second vertex;

else

not modifying the coordinate of the second vertex, and

wherein modifying the coordinate comprises;

if a value of the coordinate of the second vertex is less than a value of the corresponding coordinate of the first vertex;

then

adding a length of the texture in the direction of the coordinate;

else

subtracting a length of the texture in the direction of the coordinate.

2. The method of claim 1 wherein receiving information regarding a plurality of primitives defining an object includes receiving the plurality of vertices for the primitive in the plurality of primitives.

3. The method of claim 2 wherein determining whether a coordinate of the second vertex is more than a threshold distance away from a corresponding coordinate of the first vertex comprises:

determining a difference between the coordinate of the second vertex and the corresponding coordinate of the first vertex; and

determining whether an absolute value of the first difference is greater than or less than a threshold portion of a length of the texture in a direction of the coordinate.

4. The method of claim 3 wherein the threshold portion is one-half.

5. The method of claim 2 wherein the coordinates for the first and second vertices comprise s, t, r, and q coordinates.

6. The method of claim 1 wherein the shader hardware is a unified shader capable of executing vertex shader, geometry shader, and fragment shader instructions.

7. The method of claim 1 wherein executing the instruction to cylindrically wrap the object with the texture using a geometry shader program running on shader hardware comprises:

executing the instruction to cylindrically wrap an object with a texture using geometry shader program running on shader hardware that includes a plurality of single-instruction, multiple-data processors.

8. The method of claim 1 wherein the shader hardware is formed on a first integrated circuit and the memory is formed on a second integrated circuit.

9. The method of claim 1 wherein the memory is a register file.

10. An integrated circuit comprising:

a front end to receive a plurality of primitives defining an object, information regarding a texture, and an instruction to cylindrically wrap the object using the texture;

shader hardware to run a geometry shader program to execute the instruction to cylindrically wrap the object using the texture; and

a memory to store results generated by the shader hardware,

wherein executing the instruction to cylindrically wrap the object with the texture comprises;

selecting a first vertex from a plurality of vertices for a primitive of the object as a reference; and

for a second vertex of the primitive, for each coordinate of the second vertex;

determining whether a coordinate of the second vertex is more than a threshold distance away from a corresponding coordinate of the first vertex; and

if it is, then

modifying the coordinate of the second vertex;

else

not modifying the coordinate of the second vertex, and

wherein modifying the coordinate comprises;

if a value of the coordinate of the second vertex is less than a value of the corresponding coordinate of the first vertex;

then

adding a length of the texture in the direction of the coordinate;

else

subtracting a length of the texture in the direction of the coordinate.

11. The integrated circuit of claim 10 wherein the shader hardware is a unified shader capable of executing vertex shader, geometry shader, and fragment shader instructions.

12. The integrated circuit of claim 10 wherein the shader hardware comprises a plurality of single-instruction, multiple-data processors.

13. The integrated circuit of claim 11 wherein the integrated circuit is a graphics processor further comprising:

a geometry circuit to receive the instruction to cylindrically wrap the object using the texture and to direct the shader hardware to run a geometry shader program to execute the instruction to cylindrically wrap the object using the texture, the object comprising a plurality of primitives; and

a rasterizer to receive the plurality of primitives from the shader hardware and to determine which pixels are covered by each of the plurality of primitives.

14. A method of processing graphics information comprising:

on an integrated circuit;

receiving information for a texture, the texture having a first length in a first dimension;

receiving information regarding an object including a primitive, the primitive comprising a plurality of vertices including a first vertex and a second vertex;

selecting a first vertex of the primitive as a reference;

for a second vertex of the primitive, for each coordinate of the second vertex;

determining whether a coordinate of the second vertex is more than a threshold distance away from a corresponding coordinate of the first vertex; and

if it is, then

modifying the coordinate of the second vertex;

else

not modifying the coordinate of the second vertex

wherein modifying the coordinate comprises;

if a value of the coordinate of the second vertex is less than a value of the corresponding coordinate of the first vertex;

then

adding a length of the texture in the direction of the coordinate;

else

subtracting a length of the texture in the direction of the coordinate.

15. The method of claim 14 wherein determining whether a coordinate of the second vertex is more than a threshold distance away from a corresponding coordinate of the first vertex comprises:

determining a first difference between the coordinate of the second vertex and the corresponding coordinate of the first vertex; and

determining whether an absolute value of the first difference is greater than or less than a threshold portion of the first length.

16. The method of claim 14 wherein the coordinates for the first and second vertices comprise s, t, r, and q coordinates.

17. The method of claim 14 wherein the threshold value is one half of a length of the texture in the direction of the coordinate.

18. The method of claim 14 further comprising:

before selecting a first vertex of the primitive as a reference, sorting the plurality of vertices.