Point of collection
The point of collection (PoC), more officially known as the Item Get Border Line, is an invisible line that's about 1/4–1/5 of the way down the screen; the exact location depends on the character selected.
This was one of the big changes to the Embodiment of Scarlet Devil; there, the PoC is only enabled while at full power. In Perfect Cherry Blossom, the same applies, except it is enabled in the Extra and Phantasm stages regardless of power level. In Imperishable Night, the PoC is enabled while at full power, when focused, or at all times when playing as Magic Team or solo Marisa (but not solo Alice).
Starting from Mountain of Faith, this function is always enabled, regardless of power level, character, and stage. At the start of the first stage, the line is visible for a short period of time, though not if you're watching a replay. This has been standardised throughout to the latest game.
If you're at or above this line, most types of items will be dragged at a moderate speed to the character. Exceptions include Undefined Fantastic Object UFO items and Ten Desires spirits. Summoned UFOs also disable auto-collecting altogether while they are present, as the UFO will auto-collect the items instead.
If you go below the line, any items already moving toward you will still be auto-collected, but any new items that appear will not unless you return above the line. The height where point items are worth their maximum value is the same height as or slightly below this line, depending on the game. Before Undefined Fantastic Object, any auto-collected items heading towards you will still lose value as you retreat from the line. Undefined Fantastic Object also forces a max value auto-collect at the end of every stage boss fight, regardless of where you are on the screen.