# vkCmdPushConstants(3) Manual Page

## Name

vkCmdPushConstants - Update the values of push constants

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## C Specification

To update push constants, call:

    // Provided by VK_VERSION_1_0
    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

When a command buffer begins recording, all push constant values are undefined. Reads of undefined push constant values by the executing shader return undefined values.

Push constant values can be updated incrementally, causing shader stages in `stageFlags` to read the new data from `pValues` for push constants modified by this command, while still reading the previous data for push constants not modified by this command. When a bound pipeline command is issued, the bound pipeline’s layout must be compatible with the layouts used to set the values of all push constants in the pipeline layout’s push constant ranges, as described in Pipeline Layout Compatibility. Binding a pipeline with a layout that is not compatible with the push constant layout does not disturb the push constant values.

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

- VUID-vkCmdPushConstants-offset-01795
  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

- VUID-vkCmdPushConstants-offset-01796
  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`

- VUID-vkCmdPushConstants-offset-00368
  `offset` must be a multiple of `4`

- VUID-vkCmdPushConstants-size-00369
  `size` must be a multiple of `4`

- VUID-vkCmdPushConstants-offset-00370
  `offset` must be less than `VkPhysicalDeviceLimits`::`maxPushConstantsSize`

- VUID-vkCmdPushConstants-size-00371
  `size` must be less than or equal to `VkPhysicalDeviceLimits`::`maxPushConstantsSize` minus `offset`

Valid Usage (Implicit)

- VUID-vkCmdPushConstants-commandBuffer-parameter
  `commandBuffer` must be a valid VkCommandBuffer handle

- VUID-vkCmdPushConstants-layout-parameter
  `layout` must be a valid VkPipelineLayout handle

- VUID-vkCmdPushConstants-stageFlags-parameter
  `stageFlags` must be a valid combination of VkShaderStageFlagBits values

- VUID-vkCmdPushConstants-stageFlags-requiredbitmask
  `stageFlags` must not be `0`

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

- VUID-vkCmdPushConstants-commandBuffer-recording
  `commandBuffer` must be in the recording state

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

- VUID-vkCmdPushConstants-videocoding
  This command must only be called outside of a video coding scope

- VUID-vkCmdPushConstants-size-arraylength
  `size` must be greater than `0`

- VUID-vkCmdPushConstants-commonparent
  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 | Video Coding Scope | Supported Queue Types | Command Type
--- | --- | --- | --- | ---
Primary Secondary | Both | Outside | Graphics Compute | State

## See Also

VK_VERSION_1_0, 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 2014-2025 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0