Flight - Angle that separates level flight from up/down

[RCgothic]

Hello playground, slight conundrum!

I can't find any suggestion of what angle constitutes level flight in the rules (http://www.d20srd.org/srd/movement.htm).
Note that this is NOT to be confused with max angle of climb for a given agility class - an angle which is UP should be the same for a good flier as for a clumsy one (even 'Perfect' cares what angle constitutes DOWN.)

This has become relevant because one of my characters has found herself 3000ft up with a fly speed and would like to glide at a shallow-ish angle at double speed to cover more ground quickly.


Is there a ruling somewhere?
If not, these are my thoughts, please discuss:


I've thought of ways both a high and shallow angle could be abused, and have prepared diagrams to help:

Up Angle Abuse:
http://img.photobucket.com/albums/v723/rcgothic/ClimbShenannigans.png
The obvious starting point is that 45' to horizontal constitutes 'UP'. However I believe there are a number of reasons it should be shallower than that - a poor or clumsy flier could never achieve an 'UP' angle if this were the case. This image also shows how with a 45' angle as 'UP', you could then gain more height by flying 'level' at 45' up and regular speed rather than directly up at half speed, which seems abusive to me. The maximum up angle that doesn't break the 'half movement up' mechanic is 30' as shown. I also don't think the airspace can be considered as 5ft cube-space, for a start because that makes the 60' max climb angle of 'Average' impossible, and also because it makes the up/down angles too steep to be satisfactory.

Down Angle Abuse:
http://img.photobucket.com/albums/v723/rcgothic/GlideShenannigans.png
This diagram needs a bit more explanation. It shows a comparison between level flight (100ft) vs a potential path you could take by flying up a bit and then gliding down if the distinction between up/down and level is made too shallow. During the up segment, a horizontal flier would cover twice that distance, to the second dot on the horizontal dashed line. However, during the remaining movement this could be more than made up for by double movement over a shallow glide angle, putting up/down ahead of level flight over a horizontal distance.

Therefore this diagram shows that the angle for not-level flight needs to be at least 15'. Any more than that and you can gain substantial range over pure level flight by flying up a bit before gliding down. 15' gives a less than 2% increase, but I don't think that's worth bothering about.

The difference between 15' and 30' is a 93% increase in horizontal speed if you already start from a height and a 73% increase respectively.

My thoughts:
I'd like to use 15' because even a shallow angle can have a strong effect on velocity, and I think it gives a more natural feeling glide at double speed. On the inverse, 15' is still quite steep and justifies additional effort, thus half speed - try running up a 15' slope on a treadmill for any length of time! But an argument could be made for anything between 15 and 30' I think.

Possibilities:
http://img.photobucket.com/albums/v723/rcgothic/Angles.png

What does the playground think?

[Spuddles]

I don't really think requiring what, 200 feet?, of horizontal space to climb the same height as a vertical climb very abusive. If you can already climb like that in aerial combat unimpeded or interrupted, then really any flight speed will basically be abusive.

[RCgothic]

I don't really think requiring what, 200 feet?, of horizontal space to climb the same height as a vertical climb very abusive. If you can already climb like that in aerial combat unimpeded or interrupted, then really any flight speed will basically be abusive.

I think you may have got the wrong end of the stick - If 45' is the angle that separates level from up, then you can gain 1.4ft by flying 'level' for every 1ft you can gain by flying directly 'up'. As it doesn't cost any movement to turn, you can fly upwards in a tight spiral faster than you can fly directly up - that mechanic would therefore be broken.

And in addition to covering a greater distance vertically, you get to go horizontally as well. It's just all-round superior to fly 'level' (if level is defined as horizontal +/-45') than to fly directly up.

Also, poor and clumsy could never achieve an angle great enough to be 'up', in spite of having an 'up' speed of half. So on the one hand you say they can go 'UP' at half speed, but on the other you say they can never do that anyway?

45' as UP just doesn't make any sense.

[Spuddles]

An average flyer has to spend 5 feet of move for every 45 degrees of turn it wants to make, 5 feet of move before starting a climb, and must maintain a minimum forward speed of half their fly speed. With a fly speed of 30 feet, you have to spend 15 feet moving forward and 5 feet beginning your climb, which leaves you with 10 feet of vert distance to move. Mind that once you accumulate 45 feet of turning in your upwards spiral, you accumulate another 5 feet of cost.

Or are you using PF or something?

[ThiagoMartell]

From what I understand, the flight rules already cover this. Then again, they are fairly complicated and I'm not sure if I really followed the OP, so I could be wrong.

[RCgothic]

An average flyer has to spend 5 feet of move for every 45 degrees of turn it wants to make, 5 feet of move before starting a climb, and must maintain a minimum forward speed of half their fly speed. With a fly speed of 30 feet, you have to spend 15 feet moving forward and 5 feet beginning your climb, which leaves you with 10 feet of vert distance to move. Mind that once you accumulate 45 feet of turning in your upwards spiral, you accumulate another 5 feet of cost.

Or are you using PF or something?

You only have to spend movement to turn in place. To turn normally you need only move the prerequisite distance first - eg 5ft up@45', turn right 90', 5ft up@45' etc. The spiral is less tight for less agile fliers, but it's still a faster ascent than a direct climb.

@Martell: The rules don't state what the differentiation between up/down and level flight is, only the maximum angle of climb. eg a good flier can fly straight up, but what angle do they start to take a movement penalty at? Clumsy fliers can't even exceed 45', yet they're still stated to take a movement penalty when flying 'up'. What direction is 'up'? I'm just trying to establish what would be sensible.

[Spuddles]

Huh, it looks like for anything with less than good maneuverability, the only angle they can move up is at 60 or 45 degrees:

Up Angle
The angle at which the creature can climb.

It doesn't say that you can climb at any other angles. Climbing at 30 degrees can't be done; that is not a 60 degree climb. Leveling up at 30 degrees? That doesn't make sense.


Regardless, you still have to maintain minimum forward speed, but now I am not so sure what counts as forward speed.

[RCgothic]

Huh, it looks like for anything with less than good maneuverability, the only angle they can move up is at 60 or 45 degrees:

Up Angle
The angle at which the creature can climb.

It doesn't say that you can climb at any other angles. Climbing at 30 degrees can't be done; that is not a 60 degree climb. Leveling up at 30 degrees? That doesn't make sense.


Regardless, you still have to maintain minimum forward speed, but now I am not so sure what counts as forward speed.

Why wouldn't a creature that can fly level or at 60' not be able to fly at anything in between. That's a horrifically broken interpretation of the rules (not saying wrong - just broken). O.o

Minimum forward speed has to be your distance covered regardless of direction. The agilities which have a minimum flying speed can't hover or reverse, so this must be forward. It can't be horizontal distance covered, again because of up angle. If you fly up at 45' and move at half speed, your horizontal speed will be less than half speed. Therefore if minimum forward speed referred only to horizontal distance covered the rules would break - one rule says you may do a thing, whilst another says you would stall if you did that thing.

[Spuddles]

Minimum forward speed has to be your distance covered regardless of direction. The agilities which have a minimum flying speed can't hover or reverse, so this must be forward. It can't be horizontal distance covered, again because of up angle. If you fly up at 45' and move at half speed, your horizontal speed will be less than half speed. Therefore if minimum forward speed referred only to horizontal distance covered the rules would break - one rule says you may do a thing, whilst another says you would stall if you did that thing.

You may have to double move on the rounds you fly up. "minimum forward speed" sounds like velocity to me; I rule that you have to move that far in a round in a single direction; none of the spiralling stuff. Though I suppose a RAW interpretation would let you move in a spiral, given that all movement forward is, well forward movement.

[RCgothic]

Technically, it doesn't say half of what speed is minimum forward speed. You could say that moving 20ft is less than half of a double-move of 60ft, despite being greater than half of a base movement of 30ft and therefore you would stall. That would be a restrictive and ridiculous reading, but it's an interpretation.

These rules seem very poorly formulated. :smallfrown:

[Answerer]

And these are why tabletop games that attempt to simulate actual, three-dimensional flight are doing it wrong.

None of this should ever come up while trying to adjudicate these rules. And I say this as an engineer who works with angles like these on a daily basis and is very comfortable with the mathematics involved.

[jindra34]

Your decision to remove the spacing units of DnD kinda hinders you here. An up angle is any in which you gain altitude (down being lose altitude instead) capped at no stepper than the angles given in the table. And if you measure in 5ft cubes you can reasonably assess such periods.

Edit For Clarity: Imagine space as made up of the cubes and you can only move by going to a different corner of the same cube. That will make it easy to tell what is upward movement and downward movement. Calculating final angles of ascent and descent not so easy.

[ericgrau]

In short there is no concrete answer for this by RAW or physics. It depends on several unknowns such as your player's drag coefficient, weight and the efficiency of conversion from vertical movement to horizontal. If we remove drag then his theoretical horizontal speed is infinite because he never stops accelerating.

An efficient gliding craft can go over 300 mph (a little under 3000 feet per round) whereas a hang glider might go 35 mph (a little under 350 feet per round). OTOH birds don't tend to go over 80 mph even in a dive; you need to be much larger for that. The power generated from the dive is completely independent of the creature's normal fly speed, so whatever your player's original fly speed was has only a little effect.

Normally I would count 1 square of upward movement as 2 squares, and 1 square of downward movement as 1/2 square. Then find the hypotenuse for the amount of movement consumed. A presolved table could be helpful. But this has nothing to do with increasing horizontal speed with a dive. I'd stick to this in combat when there isn't time to accelerate anyway.

For a long glide like what your player wants to do you simply need to make something up. How about 200 feet per round in winged humanoid form, 400 feet per round in winged animal form, 5 vertical feet per 20 horizontal feet, the player's fly speed has no significant impact, wingless magical flight may not glide, and call it a day?

[Curmudgeon]

You're trying to make this harder than it needs to be. D&D movement is all about counting the 5' squares you move through. If your up movement is at half speed, count upward squares double (including diagonally upward, of which half are already doubled once; remember that in D&D distances are doubled via normal math). Down movement is at double speed, so count downward squares as halves.

The other aerial movement factors come in as maneuverability limit checks. Total up your up/down squares and your horizontal squares, divide them, and see if they're within the up/down angle limits. (Anything with vertical movement less than or equal to horizontal movement is within 45 degrees. 60 degrees is messier: the ratio of vertical to horizontal needs to be no more than 1.732.) If you don't fit these limits, your character can't move that way. The "Maximum turn" figure is per move action (since D&D doesn't have "facing", it can't be in place); that will limit "tight spirals". The "Between down and up" limit is for all movement, square by square.