# vkCmdPushConstants(3) Manual Page

## Name

vkCmdPushConstants - Update the values of push constants

## C Specification

To update push constants, call:

    void vkCmdPushConstants(
        VkCommandBuffer                             commandBuffer,
        VkPipelineLayout                            layout,
        VkShaderStageFlags                          stageFlags,
        uint32_t                                    offset,
        uint32_t                                    size,
        const void*                                 pValues);

## Parameters

- `commandBuffer` is the command buffer in which the push constant update will be recorded.

- `layout` is the pipeline layout used to program the push constant updates.

- `stageFlags` is a bitmask of VkShaderStageFlagBits specifying the shader stages that will use the push constants in the updated range.

- `offset` is the start offset of the push constant range to update, in units of bytes.

- `size` is the size of the push constant range to update, in units of bytes.

- `pValues` is a pointer to an array of `size` bytes containing the new push constant values.

## Description

| Note As `stageFlags` needs to include all flags the relevant push constant ranges were created with, any flags that are not supported by the queue family that the VkCommandPool used to allocate `commandBuffer` was created on are ignored.

Valid Usage

- For each byte in the range specified by `offset` and `size` and for each shader stage in `stageFlags`, there must be a push constant range in `layout` that includes that byte and that stage

- For each byte in the range specified by `offset` and `size` and for each push constant range that overlaps that byte, `stageFlags` must include all stages in that push constant range’s VkPushConstantRange::`stageFlags`

- `offset` must be a multiple of `4`

- `size` must be a multiple of `4`

- `offset` must be less than `VkPhysicalDeviceLimits`::`maxPushConstantsSize`

- `size` must be less than or equal to `VkPhysicalDeviceLimits`::`maxPushConstantsSize` minus `offset`

Valid Usage (Implicit)

- `commandBuffer` must be a valid VkCommandBuffer handle

- `layout` must be a valid VkPipelineLayout handle

- `stageFlags` must be a valid combination of VkShaderStageFlagBits values

- `stageFlags` must not be `0`

- `pValues` must be a valid pointer to an array of `size` bytes

- `commandBuffer` must be in the recording state

- The `VkCommandPool` that `commandBuffer` was allocated from must support graphics, or compute operations

- `size` must be greater than `0`

- Both of `commandBuffer`, and `layout` must have been created, allocated, or retrieved from the same VkDevice

Host Synchronization

- Host access to `commandBuffer` must be externally synchronized

- Host access to the `VkCommandPool` that `commandBuffer` was allocated from must be externally synchronized

Command Properties

Command Buffer Levels | Render Pass Scope | Supported Queue Types | Pipeline Type
--- | --- | --- | ---
Primary Secondary | Both | Graphics Compute |

## See Also

VkCommandBuffer, VkPipelineLayout, VkShaderStageFlags

## Document Notes

For more information, see the Vulkan Specification

This page is extracted from the Vulkan Specification. Fixes and changes should be made to the Specification, not directly.

## Copyright

Copyright (c) 2014-2020 Khronos Group. This work is licensed under a Creative Commons Attribution 4.0 International License.