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Does the ground knock the victim prone, like a wall would on a vertical (ground based) shield bash? (if not why not)?
Does the attacker crash into the ground? (if not why not)?
Here is the character (attacker):
Str 22
Dex 10
Con 18
Int 14
Wis 10
Chr 15
Dwarf
Dragon Disciple 9 (with wings)
Ftr 3
Rng 2
Sor 1
EKn 5
Character has feats:
Improved Shield Bash
Shield Slam
Shield Master
Fly Skill is 20
And we are playing core rules but, might look at ultimate combat if it answers this (however don't want to add additional feats in our game).
Also, and thoughts on suitable feats that could improve this process would be greatly appreciated!
System doesn't have this level of resolution, it's left up to the GM.
My answer would be no. There are no angles of attack or anything like that in the game. You are simply in a square, and the creature moves the opposite direction away from you if there is available space to be moved. Shield Slam specifically stipulates that if he hits an object that he falls prone. However, the game was not designed with flying creature in mind to fly above and try to Shield Slam their opponents from above (which is basically what you're doing). It would be unwise to rule that this just automatically results in the character being made prone, and I can see it being rife for abuse.
Instead, I would simply rule that the character was forced along the ground away from you. If you were directly above he would move in a random direction.
That is like saying, there is a wall there, the player got pushed in either direction not into the wall.
My thoughts are the game does semi answer this (and I ambiased) but, the wingover and hoover feats would infact seem to address this as does the flying skill, which is a DC 20 turn 180 degrees or hoover.
If I drop a piano on your character are you knocked prone? Of course you are. But, that is not D&D style, what about if a dragon falls on you, are you knocked prone.
System doesn't have this level of resolution, it's left up to the GM.
My answer would be no. There are no angles of attack or anything like that in the game. You are simply in a square, and the creature moves the opposite direction away from you if there is available space to be moved. Shield Slam specifically stipulates that if he hits an object that he falls prone. However, the game was not designed with flying creature in mind to fly above and try to Shield Slam their opponents from above (which is basically what you're doing). It would be unwise to rule that this just automatically results in the character being made prone, and I can see it being rife for abuse.
Instead, I would simply rule that the character was forced along the ground away from you. If you were directly above he would move in a random direction.
The argument here would be that it is the opposite direction in relation to the character performing the maneuver; if the PC was 45 degrees from the enemy (AKA, adjacent while 5 feet in the air), the opposite direction of going airborne would be to be 5 feet in the ground. It makes no sense to apply it to one set of rules and not the other, especially when it's quite obvious what the intent is supposed to be.
Opponents who cannot move back due to a wall or other surface are knocked prone after moving the maximum possible distance. You may choose to move with your target if you are able to take a 5-foot step or to spend an action to move this turn.
That being said, pushing at 45 degree angles will result in awkward movement. If a creature is flying 5 feet high and otherwise adjacent to a medium-sized ground enemy, the creature will have to succeed by an additional 10 to actually push the creature back two squares.
Even so, I think it's good for Bull Rush to get used in this manner, as it gives a nice Martial option.
That is like saying, there is a wall there, the player got pushed in either direction not into the wall.
My thoughts are the game does semi answer this (and I ambiased) but, the wingover and hoover feats would infact seem to address this as does the flying skill, which is a DC 20 turn 180 degrees or hoover.
If I drop a piano on your character are you knocked prone? Of course you are. But, that is not D&D style, what about if a dragon falls on you, are you knocked prone.
Wingover and Hoover feats have nothing to do with this situation. You're talking about "attacking a character at a 15 degree angle", but no rules for such a thing exist. The rules from wingover and hover are about flying and turning, and only apply to them. I'm not even sure why you're bringing these up because they have no relation to the real question.
Also, for what it's worth dropping a piano or a dragon on a character doesn't knock them prone. Check out the falling object rules and you will find no mention of being knocked prone.
Just as characters take damage when they fall more than 10 feet, so too do they take damage when they are hit by falling objects.
Objects that fall upon characters deal damage based on their size and the distance they have fallen. Table: Damage from Falling Objects determines the amount of damage dealt by an object based on its size. Note that this assumes that the object is made of dense, heavy material, such as stone. Objects made of lighter materials might deal as little as half the listed damage, subject to GM discretion. For example, a Huge boulder that hits a character deals 6d6 points of damage, whereas a Huge wooden wagon might deal only 3d6 damage. In addition, if an object falls less than 30 feet, it deals half the listed damage. If an object falls more than 150 feet, it deals double the listed damage. Note that a falling object takes the same amount of damage as it deals.
Dropping an object on a creature requires a ranged touch attack. Such attacks generally have a range increment of 20 feet. If an object falls on a creature (instead of being thrown), that creature can make a DC 15 Reflex save to halve the damage if he is aware of the object. Falling objects that are part of a trap use the trap rules instead of these general guidelines.
@ Darksol, I understand the implications and the positions and what vectors would normally be used here, but it's simply a situation that was anticipated by the rules (which is funny since shield slam and fly are both from the CRB). I think it's a little too strong to say that it works the way the OP wants it to, but I understand how he arrived at that conclusion. If however it is clarified to work, I would wholly support it.
Tl;dr - Grey area; no until official yes.
I see it as Claxon does.
The game is not fine-grained enough for each and every possibility to come up to have a dedicated rule to it. This means ultimately its up to the DM to make a judgement call.
In this case here i'd also go with "No" with the same reasoning as Claxon.
I didn't realize a Bull Rush effect, which specifically mentions creatures are prone if they are effectively moved past an immovable surface, and a falling object, are the same thing.
So, Pot, meet Kettle. Falling Objects don't perform a Bull Rush, and that is the mechanical reason why they don't. Even if they did, they wouldn't actually deal any damage as per the Bull Rush rules. Realistically speaking, it makes no sense, but them's the breaks.
And honestly, it's not that strong at all to allow somebody to be able to knock an enemy Prone from an airborne attack. Nobody that I've seen, both in-game, and on the forums, has created a Bull Rush build that is actually effective across levels of play. It's a low-level drastic measure tactic, tops if used standardly. Used this way, it's actually nice to have.
You could accomplish this all the same with a Flying Trip build, but a lot of creatures are immune to that (and of course, the same goes for Bull Rush). Even if you did try it, then you aren't dealing damage on top of it unlike this build.
I didn't realize a Bull Rush effect, which specifically mentions creatures are prone if they are effectively moved past an immovable surface, and a falling object, are the same thing.
So, Pot, meet Kettle. Falling Objects don't perform a Bull Rush, and that is the mechanical reason why they don't. Even if they did, they wouldn't actually deal any damage as per the Bull Rush rules. Realistically speaking, it makes no sense, but them's the breaks.
Are you agreeing with me or not? I'm confused. I didn't bring it up in the first place, the OP did. I was simply responding to his statement.
Does that mean someone with a decent acrobatics score can jump and bull rush while in the air in order to effectively perform a trip maneuver?
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Wingover and Hoover feats have nothing to do with this situation.
You're talking about "attacking a character at a 15 degree angle", but no rules for such a thing exist. The rules from wingover and hover are about flying and turning, and only apply to them. I'm not even sure why you're bringing these up because they have no relation to the real question.
Referencing these feats, I'm talking about not running into the ground. The flight skill, as the feats suggest, should stop running into the ground.
As for the falling object damage very useful but, I'm specifically talking about in real life if a piano is dropped on you are you knocked prone. Of course you are.
If a dragon wants to land on you, with the intent of knocking you prone are you knocked prone, I think CMD has an influence there but, the average defender is going to fail that.
The 15 degree angle is irrelevant according to existing rules. It would be seen as straight down as combat resolves. Because squares resolve 0 degrees, 45 degrees, and straight down (90 degrees). However technically, characters run at 15 degree angles all the time. But, for resolving combat it is either 0, 45, or 90....
To clarify, I said 15 degrees to suggest it I wasn't a rock falling but, an actually guided flying character able to change directions and stop. The combat would resolve straight down for the purposes of a shield bash.
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If the rules don't say he goes prone, why would he?
Logic has no place in a game like this :P
If the rules don't say he goes prone, why would he?
Logic has no place in a game like this :P
Alexd1976, if a character bull rushes a monster into a wall, isn't the monster knocked prone?
specifically, take: dwarf bull rushes goblin into wall is goblin knocked prone?
If a dragon disciple bull rushes while flying straight down on your head, doesn't the ground act like a wall, and therefore, aren't you knocked prone?
If the rules don't say he goes prone, why would he?
Logic has no place in a game like this :P
Alexd1976, if a character bull rushes a monster into a wall, isn't the monster knocked prone?
specifically, take: dwarf bull rushes goblin into wall is goblin knocked prone?
If a dragon disciple bull rushes while flying straight down on your head, doesn't the ground act like a wall, and therefore, aren't you knocked prone?
Actually no. Bullrush does not cause people to go prone. Only shield slam actually causes people to go prone, because the feat specifically says it does.
Do not apply real life events to the game, it doesn't work. By the game rules, falling objects do not cause creatures to fall prone regardless of whether or not they are pianos or dragons. If you want to apply real life, dragons don't exist and neither do magically flying humans. You can't pick and choose when to apply the real life metric to the game because it's convenient to you. Simply follow the rules.
If the rules don't say he goes prone, why would he?
Logic has no place in a game like this :P
Alexd1976, if a character bull rushes a monster into a wall, isn't the monster knocked prone?
specifically, take: dwarf bull rushes goblin into wall is goblin knocked prone?
If a dragon disciple bull rushes while flying straight down on your head, doesn't the ground act like a wall, and therefore, aren't you knocked prone?
Actually no. Bullrush does not cause people to go prone. Only shield slam actually causes people to go prone, because the feat specifically says it does.
Do not apply real life events to the game, it doesn't work. By the game rules, falling objects do not cause creatures to fall prone regardless of whether or not they are pianos or dragons. If you want to apply real life, dragons don't exist and neither do magically flying humans. You can't pick and choose when to apply the real life metric to the game because it's convenient to you. Simply follow the rules.
This.
If your GM wants to account for flight, and treat the ground as a wall, he can do that.
A wall isn't the floor, and the floor isn't a wall. So RAW, no going prone.
Would I rule this way? Probably.
They shouldn't go prone because normally you are knocking them off balance from the side, whereas coming down on them, it's just applying force directly onto their head... so it's easier to stay up.
Valid points. Thank you!
If the rules don't say he goes prone, why would he?
Logic has no place in a game like this :P
Alexd1976, if a character bull rushes a monster into a wall, isn't the monster knocked prone?
specifically, take: dwarf bull rushes goblin into wall is goblin knocked prone?
If a dragon disciple bull rushes while flying straight down on your head, doesn't the ground act like a wall, and therefore, aren't you knocked prone?
Actually no. Bullrush does not cause people to go prone. Only shield slam actually causes people to go prone, because the feat specifically says it does.
Do not apply real life events to the game, it doesn't work. By the game rules, falling objects do not cause creatures to fall prone regardless of whether or not they are pianos or dragons. If you want to apply real life, dragons don't exist and neither do magically flying humans. You can't pick and choose when to apply the real life metric to the game because it's convenient to you. Simply follow the rules.
This.
If your GM wants to account for flight, and treat the ground as a wall, he can do that.
A wall isn't the floor, and the floor isn't a wall. So RAW, no going prone.
Would I rule this way? Probably.
They shouldn't go prone because normally you are knocking them off balance from the side, whereas coming down on them, it's just applying force directly onto their head... so it's easier to stay up.
Opponents who cannot move back due to a wall or other surface are knocked prone after moving the maximum possible distance.
I like purposefully ignoring the feat's wording when it's convenient for making my point. It makes my argument seem infallible and completely arbitrary.
Walls and Floors don't have to be equal except for it being a surface. A surface is a surface is a surface; although this does involve table variation, if a table varies on whether floors and walls are similar sorts of surfaces, well...if you're going to argue that the floor isn't a surface, then quite frankly every PC would be falling or flying, and therefore whenever a PC moves at all, they must use Flying rules.
Except they don't. It also makes a lot of the combat section regarding movement irrelevant so if you think scrapping a fair amount of the book just to deny a player his feat's ability, the way that feat is supposed to work, then I really wonder what kind of game you're playing (Munchkin works that way. Pathfinder, not so much).
Darksol, that is how I saw it.
If the rules don't say he goes prone, why would he?
Logic has no place in a game like this :P
Alexd1976, if a character bull rushes a monster into a wall, isn't the monster knocked prone?
specifically, take: dwarf bull rushes goblin into wall is goblin knocked prone?
If a dragon disciple bull rushes while flying straight down on your head, doesn't the ground act like a wall, and therefore, aren't you knocked prone?
Actually no. Bullrush does not cause people to go prone. Only shield slam actually causes people to go prone, because the feat specifically says it does.
Do not apply real life events to the game, it doesn't work. By the game rules, falling objects do not cause creatures to fall prone regardless of whether or not they are pianos or dragons. If you want to apply real life, dragons don't exist and neither do magically flying humans. You can't pick and choose when to apply the real life metric to the game because it's convenient to you. Simply follow the rules.
This.
If your GM wants to account for flight, and treat the ground as a wall, he can do that.
A wall isn't the floor, and the floor isn't a wall. So RAW, no going prone.
Would I rule this way? Probably.
They shouldn't go prone because normally you are knocking them off balance from the side, whereas coming down on them, it's just applying force directly onto their head... so it's easier to stay up.
Opponents who cannot move back due to a wall or other surface are knocked prone after moving the maximum possible distance.I like purposefully ignoring the feat's wording when it's convenient for making my point. It makes my argument seem infallible and completely arbitrary.
Walls and Floors don't have to be equal except for it being a surface. A surface is a surface is a surface; although this does involve table...
How about you reel in the attitude before assuming what I did when I said that.
Didn't read the feat, just read what was posted here. So, now that you have presented information I didn't have, I would be inclined to agree.
With the rules.
Not with you. You were mean and I don't like mean people.
I'm one of those "stick to the rules guys" unless it REALLY screws up the game.
This situation doesn't.
alexd1976, who are you asking to "reel in the attitude"?
For the record, I wanted a healthy debate on this subject to make sure I understood it from every perspective - I knew it was not covered by the rules. (which for the record noretoc apparently doesn't appreciate).
As for your part, I think you may have drawn irr when you said logic has no place in a game like this - I mean it's a 50/ 50 kind of thing on how that is taken.
That said if my post offended I profusely appologize, I am still new to the pathfinder system and trying to map it out. I am a very experienced GM from D&D1.0, 2.0, a little 3.5 but, I honestly know very little on the matrix in combat exceptions in pathfinder. -sorry!
alexd1976, who are you asking to "reel in the attitude"?
For the record, I wanted a healthy debate on this subject to make sure I understood it from every perspective - I knew it was not covered by the rules. (which for the record noretoc apparently doesn't appreciate).
As for your part, I think you may have drawn irr when you said logic has no place in a game like this - I mean it's a 50/ 50 kind of thing on how that is taken.
That said if my post offended I profusely appologize, I am still new to the pathfinder system and trying to map it out. I am a very experienced GM from D&D1.0, 2.0, a little 3.5 but, I honestly know very little on the matrix in combat exceptions in pathfinder. -sorry!
I assumed the line of text above the /sarcasm comment was directed at me.
I also am sorry if this was not the case.
Going from 2.0 to Pathfinder is probably better than going from 3.5 to Pathfinder. I'm still un-learning a lot of 3.5 stuff... thank your lucky stars you aren't deeply entrenched in THAT mire... :D
In any case, with what has been shown, I would now be inclined to say yes, someone flying could use the floor in the same fashion as a wall when performing this maneuver, it seems logical as long as the angle of approach was deemed appropriate by the GM.
I sometimes adhere to the rules a bit TOO much.
I would say that "move back" can be fairly vague here if any reasonable angle is involved. If the target can't move straight back, but can move generally back, for instance against a diagonal wall, then I'd say they roll along the wall instead of falling prone upon the first touch of it. The same would apply to an attack from mostly above. If there is a bit of an angle going in one direction, then the player just moves along that angle. If the attack is almost completely from above though, I would treat the ground as a surface.
alexd1976, who are you asking to "reel in the attitude"?
For the record, I wanted a healthy debate on this subject to make sure I understood it from every perspective - I knew it was not covered by the rules. (which for the record noretoc apparently doesn't appreciate).
As for your part, I think you may have drawn irr when you said logic has no place in a game like this - I mean it's a 50/ 50 kind of thing on how that is taken.
That said if my post offended I profusely appologize, I am still new to the pathfinder system and trying to map it out. I am a very experienced GM from D&D1.0, 2.0, a little 3.5 but, I honestly know very little on the matrix in combat exceptions in pathfinder. -sorry!
I assumed the line of text above the /sarcasm comment was directed at me.
I also am sorry if this was not the case.
Going from 2.0 to Pathfinder is probably better than going from 3.5 to Pathfinder. I'm still un-learning a lot of 3.5 stuff... thank your lucky stars you aren't deeply entrenched in THAT mire... :D
In any case, with what has been shown, I would now be inclined to say yes, someone flying could use the floor in the same fashion as a wall when performing this maneuver, it seems logical as long as the angle of approach was deemed appropriate by the GM.
I sometimes adhere to the rules a bit TOO much.
Neverwinter nights, I did 3.5... just not unlearning as much. but, I DM'd 1.0 and 2.0 for over a decade so...
So wait, you read what was posted here, and the relevant feat description, which I cited to you again, was posted here before I reiterated it...that's confusing and contradicting, but that's beside the point:
You can disagree with it because you don't like it, and that's fine. In fact, I never cared if anyone liked it or not, because people can have their opinions about certain things, and I agreed with several of those opinions.
But it's not acceptable to deem what you don't like as not an official rule; it might fly in a home game, where you can houserule things, but when you're giving actual answers to how a rule is supposed to work, as designed/intended by the developers, you use the official rule, and is doubly true for when players ask for advice in PFS, end of story. Opinions aren't as respected in Rules As Worded, especially when it's quite clear, both RAW and RAI, that, for example, the floor of a box (which is essentially "the room") contains a product (creatures, environmental factors, etc.) just as much as the side (wall) of the box.
@ Melkiador: "Move Back" isn't explicitly defined in the rules regarding movement via Bull Rush or similar abilities; it's actually not stated to be a direct move-back, yet every single GM that I know that runs it plays it as such. (It was actually played that way in a couple PFS Scenarios that I saw during Gencon, so it's quite clear that's the RAI of it, at least in PFS, which adheres to the RAW quite literally.) But given how it works on a flat surface (that is, characters on equal ground), it's unreasonable to determine that it can't work the same way just because we add the third dimension, and the angles of which we attack.
I would say that "move back" can be fairly vague here if any reasonable angle is involved. If the target can't move straight back, but can move generally back, for instance against a diagonal wall, then I'd say they roll along the wall instead of falling prone upon the first touch of it. The same would apply to an attack from mostly above. If there is a bit of an angle going in one direction, then the player just moves along that angle. If the attack is almost completely from above though, I would treat the ground as a surface.
I disagree, technically speaking if my character shield bashes your character, I can knock him 5' in the opposite direction from me. 5' in the opposite direction is the floor... Hence, you would be prone... that is (or at east should be) 100% certain in this healthy debate.
If the angles line up to suggest my character can shield bash you into the floor, then the floor is 100% inturn treated as a wall. If inturn it is treated as a wall, you are 100% knocked prone....
Actually, can anyone quote me the rule on where exactly the 5' knock from a shield bash has to place a character? My assumption is straight back but, this is a dragon disciple. I mean take an enlage potion, in standard nonflying combat with a base unmodified strength 22 and if you are a stringy wizard, I am pretty sure, I can bash you into any square I want within 180 degree arc.
*** I was posting this while Darksol posted, I believe he answered it***
Of course logic DOES actually have a place in this game. Game Masters are expected to say, you dwarf is NOT Mighty Mouse, and you can NOT have a 40 strength, and you can NOT grab a Storm Giant by his toe and beat him from side to side against the ground till he yields.... By the way 40 strength means you can lift a storm giant without his consent.... just saying logic has a place in the game.... that is WHY DC's are GM discretion, they just give you an idea what reasonable numbers might be....
And Darksol, thanks but, who are you saying isn't listening, I thought I was but, maybe I misunderstood.
Bull Rush page 199 core rules "A bull rush attempts to push an opponent straight back without doing any harm"
Still, straight back is the floor. And it says page 133 Core Rules; "Opponents who cannot move back due to a wall or other
surface are knocked prone after moving the maximum
possible distance." Surface would infact include the ground... if it were the attackers straight back
So, the GM, agrees with Darksol's assesment and it would infact knock target prone. More over, the target is essentially stuck prone because if he attampts to stand he is flat footed verse AoO shield bash and failing would knock him back down (unless some acrobatics are applied)... the Dwarven Dragon Disciple would need to make a DC 15 flight check to hoover and not crash into the ground following the shield bash (however)...
For players interested, this build is F3,Ranger 2, Sorcerer 1, DD9 (for wings), EK 5 (for spells and 2 extra feats). He uses a dwarven thrower so while using AoO to keep target 1 down he can range alternate targets and has a 30 AC with 300+ HP.... - with just core rules (and a 22 STR not enhanced). He can cast as a lvl 11 sorcerer... so you can imagine the buffs.
I would take alexd1976's advice and not allow you to Shield Slam someone who is standing on the ground into the ground.
The maneuvers are designed with a 2D, top-down approach, not the emulated 3D approach that flying causes (even then it's been noted that flying doesn't work the same with moving multiple diagonal squares and such, it just uses movement penalties for ascending and descending.) The game was not designed for true 3D play.
In this case, the maneuvers represent knocking someone back and them stumbling into something. It is much harder to drive or push a person downwards then to push them backwards or forwards or from the side.
Not every surface is equal. I don't allow people to swim across the ground, nor do I use climb speeds to let someone crawl faster than everyone else down the road because it's higher than their normal Move Speed. Similarly, if you were to run up and shield smash a giant spider or a spider climbing wizard clinging to the wall, I wouldn't rule that as being driven into a wall or other surface. I would rule it wasn't moved.
If, however, you wish to use this ability from an angled approach above, the fairest thing is to just move the enemy back (along the ground) in a direction away from where you hit them. If you're directly over them, then just in one, logical direction. If they hit a solid surface in that case, then they fall prone.
Again, I would just work it that way for creatures standing on the ground. If it's another flying creature or something else not braced against the surface your driving it into, then go right ahead and slam them into the earth. (Yes, I absolutely would apply this to those annoying characters with air walk and such that constantly claim to be walking around 2 to 6 inches off the floor to never set off traps.)
It does deal with arial combat there is a feat called Death from Above (read this post http://paizo.com/threads/rzs2ngri?Death-From-Above) Dungeons and Dragons switched to DC, so game masters could remove their head from their postures and think for themselves. This so obviously works, I am now certain, and it is OP - love my character!
More over, the target is essentially stuck prone because if he attampts to stand he is flat footed verse AoO shield bash and failing would knock him back down (unless some acrobatics are applied)...Maybe I'm confused. You have some talent that makes prone creatures flat-footed against your shield bash? You'd normally get a +4 against a prone target, but that doesn't make them flat-footed.
Even then, if he attempts to stand up, even if you hit with an AoO, even if you hit him with an AoO designed to trip or knock him prone, he's still prone because you're AoO preempts that. So it would do nothing (other than damage.) Assuming he survives the damage, he completes his movement and stands up. If you're in that square and he can't move, then he's moved to a legal square.
Sorry pizza lord, you are right (I am still a little new at Pathfinder combat).
and, the Dragon Disciple is still hovering, so as you attempt to stand shield bash, without an acrobatic roll or something that stops AoO from moving you upon successful attack would remain prone. and yes base damage of a Large shield with spikes....
The way I would adjudicate it per the rules is that any downward use of a Shield Slam ( directly down or at an angle into adjacent ground squares) would constitute a "solid surface" and if the free bull rush attempt is successful (it is not automatic), the the attacked creature would be prone.
Once prone they have a -4 penalty to their AC. If they attempt to stand up, they would normally face an attack of opportunity from any foes who threaten their square. There are, of course, ways to avoid this attack of opportunity. Whether or not the attack of opportunities are successful, they would be able to stand up and would not be knocked prone by the attack of opportunity even if it had some affect like the Shield Slam free bull rush.
When standing from prone, you are still considered prone, ie all of the penalties, and so cannot be knocked prone again. If the creature survives the attacks of opportunity, then they will be standing. Of course, the foe can repeat the process next round.
It is the same with a wolf who gets a free trip attempt with a successful attack. They cannot "re-trip" the character as they are standing up as they are already prone at that time.
Now there may be some abilities that say any successful attack will result in the creature remains tripped or prone, but that is not normally how it works. It is, however, a good and viable tactic.
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I think the question should be reduced to:
Is it possible to bull rush someone downward, if you're coming from above than them? I would say yes, since
A bull rush attempts to push an opponent straight back without doing any harm.
If we're both flying and I'm coming from above, I'd beat you downward. If I'm flying and you're on the ground, I'd be pushing you to the ground.
Normal bull rush gets stopped if the enemy can't be pushed further. Shield Slam handles that;
Shield Slam (Combat)
In the right position, your shield can be used to send opponents flying.
Prerequisites: Improved Shield Bash, Shield Proficiency, Two-Weapon Fighting, base attack bonus +6.
Benefit: Any opponents hit by your shield bash are also hit with a free bull rush attack, substituting your attack roll for the combat maneuver check (see Combat). This bull rush does not provoke an attack of opportunity. Opponents who cannot move back due to a wall or other surface are knocked prone after moving the maximum possible distance. You may choose to move with your target if you are able to take a 5-foot step or to spend an action to move this turn.
The floor is clearly a surface, so you the slammee goes prone.
I would take alexd1976's advice and not allow you to Shield Slam someone who is standing on the ground into the ground.
The maneuvers are designed with a 2D, top-down approach, not the emulated 3D approach that flying causes (even then it's been noted that flying doesn't work the same with moving multiple diagonal squares and such, it just uses movement penalties for ascending and descending.) The game was not designed for true 3D play.
In this case, the maneuvers represent knocking someone back and them stumbling into something. It is much harder to drive or push a person downwards then to push them backwards or forwards or from the side.
Not every surface is equal. I don't allow people to swim across the ground, nor do I use climb speeds to let someone crawl faster than everyone else down the road because it's higher than their normal Move Speed. Similarly, if you were to run up and shield smash a giant spider or a spider climbing wizard clinging to the wall, I wouldn't rule that as being driven into a wall or other surface. I would rule it wasn't moved.
If, however, you wish to use this ability from an angled approach above, the fairest thing is to just move the enemy back (along the ground) in a direction away from where you hit them. If you're directly over them, then just in one, logical direction. If they hit a solid surface in that case, then they fall prone.
Again, I would just work it that way for creatures standing on the ground. If it's another flying creature or something else not braced against the surface your driving it into, then go right ahead and slam them into the earth. (Yes, I absolutely would apply this to those annoying characters with air walk and such that constantly claim to be walking around 2 to 6 inches off the floor to never set off traps.)
I actually changed my mind on this one.
If you could normally bullrush someone into a wall and knock them prone, I see no reason why (assuming the correct angle) you couldn't just do the same thing from above, substituting floor for wall.
I _might_ consider a bonus to the targets CMB due to different centre of gravity and all (coming straight down rather than from the side), but don't really see any reason to disallow it completely.
The way I would adjudicate it per the rules is that any downward use of a Shield Slam ( directly down or at an angle into adjacent ground squares) would constitute a "solid surface" and if the free bull rush attempt is successful (it is not automatic), the the attacked creature would be prone.
Once prone they have a -4 penalty to their AC. If they attempt to stand up, they would normally face an attack of opportunity from any foes who threaten their square. There are, of course, ways to avoid this attack of opportunity. Whether or not the attack of opportunities are successful, they would be able to stand up and would not be knocked prone by the attack of opportunity even if it had some affect like the Shield Slam free bull rush.
When standing from prone, you are still considered prone, ie all of the penalties, and so cannot be knocked prone again. If the creature survives the attacks of opportunity, then they will be standing. Of course, the foe can repeat the process next round.
It is the same with a wolf who gets a free trip attempt with a successful attack. They cannot "re-trip" the character as they are standing up as they are already prone at that time.
Now there may be some abilities that say any successful attack will result in the creature remains tripped or prone, but that is not normally how it works. It is, however, a good and viable tactic.
Thanks for clarifying those rules Hendelbolaf!