---
layout: stdlib-reference
---
# ddy
## Description
Take the partial derivative of p with respect to y in screen space.
## Signature
T ddy<T>(T p)
where T : __BuiltinFloatingPointType;
vector<T, N> ddy<T, N:int>(vector<T, N> p)
where T : __BuiltinFloatingPointType;
matrix<T, N, M> ddy<T, N:int, M:int>(matrix<T, N, M> p)
where T : __BuiltinFloatingPointType;
## Generic Parameters
#### T: [\_\_BuiltinFloatingPointType](../interfaces/0_builtinfloatingpointtype-029hm/index.html)
#### N : int
#### M : int
## Parameters
#### p : [T](ddy.html#typeparam-T)
The value to take partial derivative for.
#### p : [vector](../types/vector/index.html)\<[T](../types/vector/index.html#typeparam-T), [N](../types/vector/index.html#decl-N)\>
The value to take partial derivative for.
#### p : [matrix](../types/matrix/index.html)\<[T](../types/matrix/t-0.html), [N](../types/matrix/index.html#decl-N), [M](../types/matrix/index.html#decl-M)\>
The value to take partial derivative for.
## Return value
The partial derivative of p.
## Remarks
For SPIR-V, this function maps to OpDPdy.
## Availability and Requirements
Defined for the following targets:
#### hlsl
Available in stages: `amplification`, `fragment`, `compute`, `mesh`, `miss`, `callable`, `closesthit`, `raygen`, `intersection`, `anyhit`.
#### glsl
Available in stages: `amplification`, `fragment`, `compute`, `mesh`, `miss`, `callable`, `closesthit`, `raygen`, `intersection`, `anyhit`.
#### cpp
Available in `fragment` stage only.
#### cuda
Available in `fragment` stage only.
#### metal
Available in `fragment` stage only.
#### wgsl
Available in `fragment` stage only.
#### spirv
Available in stages: `amplification`, `fragment`, `compute`, `mesh`, `miss`, `callable`, `closesthit`, `raygen`, `intersection`, `anyhit`.
Requires capabilities: `SPV_KHR_compute_shader_derivatives`, `spvMeshShadingEXT`.