I'm trying to get the shadows to come out behind the planet, but I can't. I'm using a transparent unlit quad for the grid. I thought about creating another multi-lit quad, but that doesn't work; the star gets drowned out. Any ideas?
#Any idea how to fix this shadow problem?
outer gale
worthy latch
On your grid meshrenderer set "receive shadows" to false
limpid cipher
Just create a new trapezoid quad behind the planet to fake shadow 
outer gale
Let me explain what I've tried so far without success. I'll also give you a bit of context, otherwise it’s hard to get a clear picture.
The game features procedurally generated star systems; the sun's size varies, and the positions and sizes of planets and moons vary as well. Because of this, baking fake shadows behind planets is not an option.
Currently, as mentioned, I’m using a quad to draw the grid with a custom shader, without using any complex features (like built-in shadows). I also have a quad to simulate fake fog using an UNLIT shader, which naturally doesn't cast or receive shadows.
I then thought about adding another quad specifically for the planet shadows. This is where the problem lies. I set the Surface Type to Transparent and the Blend Mode to Multiply. I tried using both a Sphere Mask and a Distance node on the UVs to create a sort of 'donut' shape to mask out the center (where the sun is), but I couldn't get it to work.
I also tried using a Custom HLSL function with an UNLIT shader to force shadow calculations inside the function, but still nothing.
I’m out of ideas. The goal is to achieve the effect found in the game IXION.
worthy latch
Oh I thought the right was what you had
limpid cipher
Maybe you can add a duplicate quad which just renders shadow and overlays that on top of the rings