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

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

Flyinghead — Sun, 22 Dec 2019 20:13:26 GMT

The following conditions are required to experience the issue:

- Depth buffer write is disabled

- The z coordinates of vertices in the vertex shader is outside the [0,1] range

- gl_FragDepth is updated in the fragment shader

Under these conditions, the geometry is not drawn.

Intel Iris Plus Graphics 640 with driver 26.20.100.7212

Here is some sample code to reproduce the issue

Based on The Practical Approach to Vulkan sample 1. I just added a bias to the z coordinate of vertices, disabled depth writes and added a line in the fragment shader to update gl_FragDepth. In this configuration, nothing is drawn.

Enabling depth buffer writes makes the geometry appear.

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

AndrewG_Intel — Tue, 24 Dec 2019 04:10:24 GMT

Hello Flyinghead,

Thank you for posting on the Intel® communities.

We are checking this thread and based on the details described we noticed that this seems to be related to the developing of a custom application/software.

In this case, we advise you to contact our Developer Zone Community so that we can check this behavior further. You can find the links below:

Intel® Developer Zone

https://software.intel.com/en-us

Registration Intel® Developer Zone

https://software.intel.com/registration/

You may also find helpful to address this inquiry with the Vulkan® Graphics API support.

Regards,

Andrew G.

Intel Customer Support Technician

A Contingent Worker at Intel