Get depth value of transparent colored entites in post processing

Hi all,

I am currently working on some post-processing in Cesium (adding a custom fragment shader via a PostProcessStage).
I am working with the “depthTexture” provided by Cesium to the fragment shader and I have some struggles working with Entities that have a color material assigned which has an alpha value smaller than 1.
If I see correctly, those entites are not part of the depthTexture. This makes sense.
However, I was wondering if there is any way to add them to the depth texture if needed.
As you are able to use the picking functions from the Scene class on them, I figured that Cesium already does something along those lines?

If it helps, I could also work with Primitives directly.