I have played piano most of my life and am now learning guitar.
On piano, I can glance at any key I happen to be hitting and immediately see what key it is based on its position within the keyboard, which has a repeating pattern of alternating black and white keys that allows easy visual identification of any note.
The same is not true of guitar. I'm finding that, for example, when forming an open G chord, I have to look at a given string and say to myself "Okay, that's the high E string - I'm on the third fret, so that's....E...F...F#....G. It's G."
I have to count half-steps every time from the string's open tuning. This seems impractical and slow.
Is there some quicker system for figuring this out? Are guitarists just memorizing, or are there tricks to this?