This happens when you have both the URP and Post Processing packages installed, and manually unpacked the _URP_VolumeSystem package. When using both these packages, the URP specific code should not be used. To remedy this, re-import the asset from the asset store to revert it to the its original configuration.
You are using an old version of the Post Processing Stack, update to the latest version through the Package Manager. A minimum of v2.0.17 is required.
This shouldn’t happen in any case, ensure that all the files in the “Shaders” folder were imported.
This can also be a false positive. In which case you can click on the error, which will highlight the shader file. Next right-click on the shader and choose “Reimport”, this will nudge things back into place. This started happening since Unity 2019.1 and is likely a bug in the revised shader compiler…
This error is thrown if there is a shader error, or a shader is missing. Be sure to have all package contents imported and use the latest Post Processing Stack version.
Fog is gray when color mode is set to Skybox
If you’re using the LWRP in Unity 2019.1.2, unfortunately this feature is broken. Due to an API change in the render pipeline. I currently know of no way to circumvent this.
This may also happen in scene view, in which case a Unity restart will fix this, or closing the scene view tab and reopening it (CTRL+1).
Fog noise or Cloud Shadows start twitching when looking directly towards the Z-axis, or at the edge where terrain meets the skybox.
This is related to using Temporal Anti-Aliasing with these effects. It requires to modify the PostProcessLayer script, so that fog executes before TAA does. Because of this I can’t provide a configurable solution.
When the camera is perpendicular to a XYZ axis, the sketch projection will appear to morph slightly.
The Fog effect may show artifacts where the skybox and objects meet.
Disable (MSAA) Anti Aliasing in your Quality Settings
When using Metal rendering on macOS, you may see the following warning: “Metal: Fragment shader missing texture binding at index X”.
Disable “Metal API Validation” in your Player Settings to resolve this. This warning will be thrown when a shader has an empty texture assigned, but is harmless.