In the description of the recent YouTube video you uploaded, you mentioned that support for the mod is basically on the side of the shaderpack developer, as most shaderpacks tend to simply replace the sky. You go on to mention that some packs "at least leave the planets".

I'm interested in having this mod work with my shaderpack, however I cannot for the life of me get more than the planets to render. I know very little about how shaders work within mods, just how they do in Iris.

There are two programs available in Iris - skytextured and skybasic. skytextured handles the sun and moon, and skybasic handles the vanilla stars and sky color. These are both rendered before terrain, skybasic runs first.

As far as I can tell, the planets are being rendered in skytextured, which is why they still show up, but I can't see the other things like dust clouds ever render while shaders are active. My guesses are either that the other effects are written to a different buffer which doesn't get factored into the shader pipeline, or that the behaviour of the shaders that render things like the dust clouds are somehow being overridden by the skybasic program.

Ah, I mention the details here, but basically it seems as of now, the only issue isn't just that the sky is getting deleted, but it is very likely the custom vertex shader I've written is incompatible with shader mods like Iris.

I'm looking into how I could make it compatible, but my knowledge of how shaderpacks operate is fairly limited and since there are no errors in the output log related to the shader, I have nothing to go off.

Currently I'm hoping my question in their Discord server on how to make a vertex shader work with Iris will be answered. However, this mention of skytextured could prove at least as some kind of starting point.

Closing this, since it's basically fixed and a different issue was discovered.