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.

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-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 Supported Queue Types Pipeline Type

Primary
Secondary

Both

Graphics
Compute

See Also

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 2014-2021 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0