Invisibility, scent and tremorsense

[zaragoz]

Hi from Spain

My party has a ninja with the vanishing trick. So I've been having some doubts about invisibility lately.

For example, on my last game, group faced some giant spiders, which have the tremorsense ability. In other situations, they have also fought against monster with the scent ability.

I assume that a creature with any of this abilities can pinpoint an invisible opponent, but it still has the 50% miss chance due to concealment.
Besides this, an invisible attacker deny the DEX bonus to those creatures, though they have this abilities, which is pretty useful for a ninja or rogue because their sneak attack.

Am I right?

[Nawtyit]

Basically with scent, they can tell if a creature is within 30ft, take a move action to note the direction, then pinpoint it if within 5ft, but still can't see it.
And with tremmorsense, they can automatically pinpoint it if within their range, but still can't see it.
If the ninja is located, they still get the 50% miss chance, and a +2 to attack sighted creatures and those creatures are denied their dex bonus.
The ninja will also get a bonus to stealth based on his movement, but still leaves tracks and displaces water.
However, he is using ki and is revealed as soon as he attacks.
So, yeah, you seem to be doing it right.

[Mathwei ap Niall]

The main thing about creatures and players with these abilities is the normally also have blind-fight as well which almost completely negates the benefits of invisibility. You no longer get the +2 to hit, the opponent retains their dexterity bonus (so you can't sneak attack them) and they reduce your 50% miss chance down to about 25%.