Concealment and Spot Checks

[Magus Coeruleus]

Hey there,

Am I missing them, or are there rules for bonuses to Hide (or penalties to Spot) for concealment?

My PCs are in a funky situation and the wizard has had his components taken away. I'm letting him improvise with a substitute for gum arabic for Invisibility, but told him it won't work perfectly, and that he thinks the subject of the spell will be mostly but not completely transparent. I thought calling it 9/10 concealment would be good.

The PCs will want to whoever's mostly Invisible sneak toward some enemies, so I'll need to use Spot checks to determine if and when they become aware of him/her. This means translating 9/10 concealment into a modifier for Spotting Difficulty DC.

Here are the pertinent mods for spotting: Contrast (+/- 5 or more); Moonlight (+5); Starlight (+10); Total darkness (impossible). Please compare to the different levels of concealment.

Concealment/Example/Miss Chance

One-quarter/Light fog; moderate darkness;light foliage/10%
One-half/Blur spell;dense fog at 5 ft. (such as obscuring mist)/20%
Three-quarters/Dense foliage/30%
Nine-tenths/Near total darkness/40%
Total/Invisibility;attacker blind; total darkness;dense fog at 10 ft./50%

I would guess that 9/10 (near total darkness) should be equal to or better than starlight (+10 DC).

What do you think?
Thanks.

 

[vanguard13]

In regards to Spot Checks with an invisible subject in dark environments, he would only been detected by monsters or things that can see invisible opponents.
If the subject is transparent like a ghost or wraith in darkness, then adjust the Spot DC accordingly with the darkness level:
Moonlight +5
Starlight +10
Total Dark (impossible)
Now if the same transparent subject in darkness opts for concealment, stack these mods to the Spot DC accordingly to availability of stuff to hide behind:
1/4, Light Fog, Mod Darkness, Light Foil= +5
1/2, dense fog to 5ft= +10
3/4, dense foil= +15
9/10, near total dark= +20
............
This will adjust the Spot DC high enough to rival the authentic Invisibility spell. It can still be circumvented by exceptionally sharp eyed characters with like +10 or +15 to their Spot skills.
Remember, even though you are invisible, being stealthy and moving around in darkness, the monsters can still hear or smell you. This could be done with Listen and Smell? checks. Listen can help determine your general area while smell can pretty much pinpoint your location especially for a guard dog.

 

[Magus Coeruleus]

Actually, the sneaking will occur in lighting conditions equivalent to broad daylight. Still, if you were sneaking toward a camp without much in the way of cover (for concealment), in broad daylight, being nearly transparent should, I think, make you harder to spot. It's not clear to me how the mods you're suggesting here would apply any differently for a normally visible person. The standard darkness level spot DC mods apply to visible characters, and the concealment mods you suggest are for environmental concealment, and thus presumably also available to visible characters. How does near-invisibility play into it?
Thanks.
MC

 

[Spatula]

d20 Modern gives the following modifiers for hiding with concealment or cover:

1/2 cover or 1/2 concealment = none, minimum needed to hide
3/4 cover or 3/4 concealment = +5 to Hide checks
9/10 cover or 9/10 concealment = +10 to Hide checks

Since a lot of 3.5 changes have been 'previewed' in Modern, it's possible these modifiers will show up in the new revision.

 

[Magus Coeruleus]

I was looking at MotW and the Camouflage spell, which makes you blend in with your surroundings, gives a +10 bonus to Hide checks. I guess that between that, the starlight +10 DC mod to spot checks, and the d20 modern +10 DC for 9/10 concealment, +10 pretty much seems the way to go here.

Thanks vanguard13 and Spatula!