I do not want to use SkySphere component, only AtmosphericFog actor!
You can disable sun disk. But, as I know, there is no easy ways to change sun disk(you can actually try to rewrite sources in AtmosphereRendering.cpp).
You can do this by creating a “Masked” material and applying it to the SkySphere. I know you said you don’t want to use it, but with the masked material it will only show the Sun Disc you want, the rest will be fully transparent.
Here is how you would set up the material:
Just like the normal skydome, you need to send the current sun rotation vector as a linear color value (Set Vector Parameter Value in blueprint) along with a scalar for Radius, Brightness, and another vector parameter for Color. Just make sure you turn off the sun disc in the Atmospheric Fog actor.
If you want to use an image instead of a disc you can use the “SkyBoxImage” material function using the same input direction vector and a vecctor2 for size with similar results.
Make sure you are rotating the sun directional light in the blueprint, otherwise the light direction and sun disc may not line up properly.
Hope that helps!