Gradient adjustment for texture mapping to non-orthonormal grid
In a computer graphics processing unit (GPU) having a texture unit, when pixel sample locations are based on a non-orthonormal grid in scene space, the texture unit receives texture space gradient values directly, e.g., from a shader unit or generates them from texture coordinates supplied, e.g., by a shader unit, and then applies a transformation to the gradient values configured to adjust the gradient values to those which would arise from the use of a orthonormal screen space grid.
1. A computer graphics method, comprising:
receiving or generating texture space gradient values for one or more primitives based on a non-orthonormal grid of sample points in a screen space with a texture unit of a graphics processing unit; and
applying a transformation to the texture space gradient values with the texture unit, wherein the transformation is configured to generate corresponding ortho-normal texture space gradient values corrected for the non-orthonormality of the sample points in screen space with the texture unit.
2. The method of claim 1 , wherein the texture unit is an application specific integrated circuit (ASIC), field programmable gate array (FPGA), or system on chip (SOC).
3. The method of claim 1 , wherein the non-orthonormal grid is an alternating column pattern.
4. The method of claim 1 , wherein the non-orthonormal grid is an alternating row pattern.
5. The method of claim 1 , wherein the non-orthonormal grid is “checkerboard” pattern.
6. The method of claim 1 , wherein the adjustment factors include per-pixel modifications.
7. The method of claim 1 , further comprising calculating corrective transformation from pixel sample location difference values with the texture unit.
8. The method of claim 1 , further comprising using the gradient values to select a level of detail from a plurality of levels of detail for a texture to be applied to one or more primitives.
9. The method of claim 8 , further comprising applying the texture to the one or more primitives.
10. The method of claim 9 , further comprising displaying images that include the texture applied to the one or more primitives with a display unit coupled to a GPU.
11. A non-transitory computer-readable medium having computer executable instructions embodied therein that, when executed, implement a method for graphics processing, the method comprising:
receiving or generating texture space gradient values for one or more primitives based on a non-orthonormal grid of sample points in a screen space with a texture unit of a graphics processing unit; and
applying a transformation to the texture space gradient values with the texture unit, wherein the transformation is configured to generate corresponding ortho-normal texture space gradient values corrected for the non-orthonormality of the sample points in screen space with the texture unit.
12. The non-transitory computer-readable medium of claim 11 , wherein the non-orthonormal grid is an alternating column pattern.
13. The non-transitory computer-readable medium of claim 11 , wherein the non-orthonormal grid is an alternating row pattern.
14. The non-transitory computer-readable medium of claim 11 , wherein the non-orthonormal grid is “checkerboard” pattern.
15. The non-transitory computer-readable medium of claim 11 , wherein the adjustment factors include per-pixel modifications.
16. The non-transitory computer-readable medium of claim 11 , further comprising calculating corrective transformation from pixel sample location difference values with the texture unit.
17. The non-transitory computer-readable medium of claim 11 , further comprising using the gradient values to select a level of detail from a plurality of levels of detail for a texture to be applied to one or more primitives.
18. The non-transitory computer-readable medium of claim 17 , further comprising applying the texture to the one or more primitives.
19. The non-transitory computer-readable medium of claim 18 , further comprising displaying images that include the texture applied to the one or more primitives with a display unit coupled to a GPU.