Depth write dynamic state required even when depth test is disabled

[squidbus]

Depth write dynamic state seems to currently be required for any draw if marked as dynamic in the pipeline, regardless of the depth test enable value. This is contrary to how it works for other state that would go unused, for example depth compare op, which is not required when depth test is disabled. According to the spec, if depth test enable is false, depth write enable has no effect and is also treated as false, so it should not be required here.

The VUID for depth compare op, which indicates it is not needed with depth test disabled:

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VUID-vkCmdDraw-None-07845

If a shader object is bound to any graphics stage or a graphics pipeline is bound which was created with the VK_DYNAMIC_STATE_DEPTH_COMPARE_OP dynamic state enabled, the current value of rasterizerDiscardEnable is VK_FALSE, and the current value of depthTestEnable is VK_TRUE, then vkCmdSetDepthCompareOp must have been called and not subsequently invalidated in the current command buffer prior to this drawing command

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The VUID for depth write enable, which does not (and which the validation layer will complain about):

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VUID-vkCmdDraw-None-07844

If a shader object is bound to any graphics stage or a graphics pipeline is bound which was created with the VK_DYNAMIC_STATE_DEPTH_WRITE_ENABLE dynamic state enabled, and the current value of rasterizerDiscardEnable is VK_FALSE, then vkCmdSetDepthWriteEnable must have been called and not subsequently invalidated in the current command buffer prior to this drawing command

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[spencer-lunarg]

@pdaniell-nv tl;dr question - If you turn off depthTestEnable, can we ignore calling vkCmdSetDepthWriteEnable

If yes, then this is just an oversight and will get a fix in the spec and VVL

if no (because of some non-obvious reason) I would update the VVL message to explain that

[pdaniell-nv]

@pdaniell-nv tl;dr question - If you turn off depthTestEnable, can we ignore calling vkCmdSetDepthWriteEnable

Yes, I think this is an oversight. vkCmdSetDepthWriteEnable should not be required if depthTestEnable is not enabled.

[spencer-lunarg]

@squidbus

• Spec fix - https://gitlab.khronos.org/vulkan/vulkan/-/merge_requests/7289
• VVL fix (once spec fix is approved) - layers: Fix depthWriteEnable dpending on depthWriteEnable Vulkan-ValidationLayers#9896