Crossing a Plain

[Stormborn]

The PCs are crossing a grassy plain. Centaurs live here and do not take kindly to tresspassers. At what point are spot checks called for by either group, how long does it take for them to come into contact once they see each other? Basically I am not used to running combats where the PCs and their opponents see each other from a long way away and need a little help before Saturday.

 

[Herzog]

Roll spot checks long before the encounter. Roll against fixed DC's (probably in the PH under skills, but you can make them DC 0 or -5 or even -10 if you like) unless one of the groups is actively trying to hide (in which case you make them roll hide checks long before the encounter)
Modify DC's (or checks) with appropriate modifiers (if one side has racial bonus to hide on plains or something simmilar)

Take the highest spot (vs lowest hide of opposition if appropriate)
multiply the difference by 10. This is the amount of feet at which the 'spotter' spots the other side.

If this is the PC's, start the encounter from there. The players will not be surprised, and might take actions to avoid the centaurs. If not, they may surprise the centaurs. This shouldn't be too different from a normal encounter.

If this is the centaurs, the centaurs aren't surprised. Let them move towards the party from the abovementioned distance, and actively hide or anything appropriate for the encounter. (a charge might be logical)
The moment a PC spots any of the centaurs (use results rolled earlier, against hide of centaurs if appropriate) end movement of all centaurs normally, and start the encounter.
First, do a surprise round. Any PC who can now spot a centaur can act in the surprise round. Then continue as normal. Assume after the surprise round all PC's are aware of the centaurs.

Hope this helps!

 

[Animal]

this was covered well in 3.0 DMG.
spotting distance (grassland terrain, little cover) - 6d6 x 20ft.
base DC to spot = 20. if a creature is hiding (keeping low in the grass, for example) it moves only at half speed and takes -2 penalty to its own spot checks, but base DC to spot it is 25 + Hide modifier instead.
concerning spotting centaurs i'd say that base DC should be around 14 (20 -4 for large size, -2 for a pack of 6+ creatures)

as to how often to make spot checks - use the rules for random wilderness encounters. for example let's say that PCs have a 12% chance to pass by scouting centaur pack each hour. so just roll d% each hour. if you roll and encounter but both parties fail their spot checks - roll survival checks to see if they notice each other's footprints or other signs of intruders' presence.

 

[Ydars]

Perhaps more important than spot checks are tracking rolls; any plains creature worth their salt will detect the party via their tracks long before they actually see them.

 

[prospero63]

All good ideas. To add to them, don't forget to factor environmental bonuses/penalties. I'd bet those centaurs know the plains, where to hide from, where to spot from, much better than the wandering PCs...

 

[prospero63]

this was covered well in 3.0 DMG.
spotting distance (grassland terrain, little cover) - 6d6 x 20ft.
base DC to spot = 20. if a creature is hiding (keeping low in the grass, for example) it moves only at half speed and takes -2 penalty to its own spot checks, but base DC to spot it is 25 + Hide modifier instead.
concerning spotting centaurs i'd say that base DC should be around 14 (20 -4 for large size, -2 for a pack of 6+ creatures)

as to how often to make spot checks - use the rules for random wilderness encounters. for example let's say that PCs have a 12% chance to pass by scouting centaur pack each hour. so just roll d% each hour. if you roll and encounter but both parties fail their spot checks - roll survival checks to see if they notice each other's footprints or other signs of intruders' presence.

Looks like this is still in the SRD:

Stealth and Detection in Plains

In plains terrain, the maximum distance at which a Spot check for detecting the nearby presence of others can succeed is 6d6×40 feet, although the specifics of your map may restrict line of sight. Plains terrain provides no bonuses or penalties on Listen and Spot checks. Cover and concealment are not uncommon, so a good place of refuge is often nearby, if not right at hand.

So it sounds like it's now 6d6X40 feet, with obvious map issues. As mentioned, I'd give some bonuses to the centaurs for most (if not all) their checks since they live here, etc. Probably something between a +2 and +5 depending on the specific circumstances.

As for how often to check, I'd use some arbitrary number as mentioned by another poster (12% or something) and I'd do all the rolls in advance of the game so that you know when you need to be more involved, etc. I'd also do the party spot rolls, as the infamous "give me a spot roll" tends to put players in extra special precaution mode...

 

[javcs]

Don't forget that Spot checks are modified by distance.
-1 for every 10ft of distance.

The 6d6x40ft is the range at which Spot checks first start getting rolled, but they probably don't make the checks at the beginning - so they keep getting rolled until both sides are aware - if one side detects the other first, then they'll probably be taking actions to not be seen, which will add additional modifiers to the Spot checks.

 

[Animal]

i really think that 20 is a DC to spot enemies at max. distance.

 

[Jhaelen]

i really think that 20 is a DC to spot enemies at max. distance.

Interesting. If that's correct, it might explain how spotting is supposed to work in 3.5. So far I've continued to use the 3.0 rules which seemed to make more sense to me.

 

[prospero63]

i really think that 20 is a DC to spot enemies at max. distance.

I don't believe that is correct. The 20 is the base DC, before modifiers are applied. It doesn't factor distance at all (IOW, the base DC to spot at max distance (1440 feet) and 100 feet is the same, 20). So to spot something at max distance, assuming no size, contrast or other factors (IOW, just the base DC and distance modifiers) the spot check is actually a DC164 (20 + 144 for the -1 penalty for each 10 feet). Similarly, the spot check at 100 feet is a DC30 (20+10 for the -1 penalty for each 10 feet).