I'm a little confused on how the process for maintaining an illusion spell like silent image.
From what I understand. I can keep the illusion going as long as I concentrate on the spell. So, if I do nothing, I can keep it going without making a roll. If I take damage I have to make the concentration check to keep it going. Of course, there's also the other situations like grappled and entangled ect..
Those examples I get, but my biggest question is how do I handle casting another spell while maintaining my illusion? Do I make a concentration check for maintaining the illusion... Do I make a concentration check on the new spell... Both? Do I even need to make a check?
Whats the rule on this?
I can keep the illusion going as long as I concentrate on the spell.
Yep!
So, if I do nothing, I can keep it going without making a roll.
Not nothing, you have to maintain the spell as a standard action. You can still take a move action, swift action, etc.
Duration - "Concentration: The spell lasts as long as you concentrate on it. Concentrating to maintain a spell is a standard action that does not provoke attacks of opportunity."
If I take damage I have to make the concentration check to keep it going.
Yep.
Concentration: "Anything that could break your concentration when casting a spell can also break your concentration while you're maintaining one, causing the spell to end."
how do I handle casting another spell while maintaining my illusion?
You don't.
Concentration: "You can't cast a spell while concentrating on another one."
Ahh. There it is. I missed the whole standard action to maintain the spell. Thanks Grick!