dsy (Pixel Shader)
Compute the rate of change in the render target's y-direction.
Syntax
Where:
- dest is a destination register.
- src is an input source register.
Remarks
| Pixel shader versions | 1_1 | 1_2 | 1_3 | 1_4 | 2_0 | 2_x | 2_sw | 3_0 | 3_sw |
|---|
| dsy | | | | | | x | x | x | x |
|---|
The rate of change computed from the source register is an approximation on the contents of the same register in adjacent pixel(s) running the pixel shader in lock-step with the current pixel. This is designed to work even if adjacent pixels follow different paths due to flow control, because the hardware is required to run a group of lock-step pixel shaders, disabling writes as necessary when flow control goes down a path that a particular pixel does not take.
The dsx, dsy instructions can simply compute therir result by looking at the current contents of the source register (per component) for the various pixels in the local area executing in the lock-step. The exact formula used to compute the gradient varies deoebgubg nb hardware but should be consistent with the way the hardware does the same operations as part of the LOD calculation process for texture sampling.