topic Hi Slawomir, in Graphics

Vulkan depth test fails when depth buffer write is disabled and gl_FragDepth is updated in fragment shader

Flyinghead — Mon, 23 Dec 2019 23:18:22 GMT

System Setup Information:
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System Used: Intel NUC7i5BN
CPU SKU: i5
GPU SKU: Intel Iris Plus Graphics 640
Processor Line: i5-7260U
Graphics Driver Version: 26.20.100.7212
Operating System: Windows 10 Home
OS Version: 10.0.17763
API: Vulkan
Occurs on non-Intel GPUs?: No (tested on NVidia, AMD, Mali, Adreno)

Steps to Reproduce:
-------------------------------

See sample code to reproduce the issue at https://github.com/flyinghead/PracticalVulkan

1. Disable depth buffer write
2. Set z coordinate of vertices in the vertex shader outside the [0,1] range
3. Update gl_FragDepth in the fragment shader to a value within [0,1]

Under these conditions, geometry isn't drawn.

Enabling depth buffer writes makes geometry appear.

Hello!

Slawomir_C_Intel — Fri, 17 Jan 2020 16:20:51 GMT

Hello!

This is Sławomir from the graphics software engineering team.

Thank you for your report! Yes, you are right, there is a bug in handling FragDepth shader output if depthWrite state is disabled.

The issue was reproduced and the team is now working on a fix.

Hi Slawomir,

Flyinghead — Fri, 17 Jan 2020 17:15:24 GMT

Hi Slawomir,

Thank you for this update. Obviously this is great news!

Thanks again

THanks

Koury__Shannon — Mon, 23 Mar 2020 13:33:33 GMT

THanks

Thanks

Koury__Shannon — Mon, 23 Mar 2020 13:46:49 GMT

Thanks