Directional Weighing

ID:1361152
 
Aug 24 2013, 6:10 pm (Edited on Aug 25 2013, 8:28 am)
What the following code does is take two directions and determines the next best direction from the first to the second.

proc/weigh_dirs(d1, d2)

    if(d2 == turn(d1, 180)) // difficult scenario, so just randomly choose clockwise or counterclockwise
        return turn(d1, pick(45,-45))

    if(d1 == d2) return d2

    switch(d1)
        if(WEST)
            if(d2 & SOUTH)
                return SOUTHWEST
            if(d2 & NORTH)
                return NORTHWEST
        if(SOUTH)
            if(d2 & WEST)
                return SOUTHWEST
            if(d2 & EAST)
                return SOUTHEAST
        if(EAST)
            if(d2 & SOUTH)
                return SOUTHEAST
            if(d2 & NORTH)
                return NORTHEAST
        if(NORTH)
            if(d2 & WEST)
                return NORTHWEST
            if(d2 & EAST)
                return NORTHEAST

        if(SOUTHWEST)
            if(d2 & SOUTH)
                return SOUTH
            if(d2 & NORTH)
                return WEST
            if(d2 & WEST)
                return WEST
            if(d2 & EAST)
                return SOUTH
        if(NORTHWEST)
            if(d2 & SOUTH)
                return WEST
            if(d2 & NORTH)
                return NORTH
            if(d2 & WEST)
                return WEST
            if(d2 & EAST)
                return NORTH
        if(SOUTHEAST)
            if(d2 & SOUTH)
                return SOUTH
            if(d2 & NORTH)
                return EAST
            if(d2 & WEST)
                return SOUTH
            if(d2 & EAST)
                return EAST
        if(NORTHEAST)
            if(d2 & SOUTH)
                return EAST
            if(d2 & NORTH)
                return NORTH
            if(d2 & WEST)
                return NORTH
            if(d2 & EAST)
                return EAST

    return d2


For example, if d1 = NORTH and d2 = WEST, the return would be NORTHWEST. This is essentially d1 | d2, yes, but what about a more complicated scenario?

What about d1 = NORTHEAST, d2 = WEST? This would return NORTH as NORTH is closest "turn" toward the desired direction. I use this bloated function to simulate a sort of "semi-homing" projectile turn:



The above code works, yes, but it's probably not the most elegant method of going about doing this. Is there some clever alternative to what I am doing other than defining almost every situation possible?

Aug 24 2013, 10:04 pm (Edited on Aug 25 2013, 2:00 am)
Your way is probably the fastest. You could shorten it by combining some of the ifs that lead to the same return value.
        if(NORTHEAST)
            if(d2 & SOUTH)
                return EAST
            if(d2 & NORTH)
                return NORTH
            if(d2 & WEST)
                return NORTH
            if(d2 & EAST)
                return EAST

//  to
        if(NORTHEAST)
            if(d2 & (SOUTH | EAST))
                return EAST
            if(d2 & (NORTH | WEST))
                return NORTH


(Time to over-complicate!)

The method I've used to determine which way to turn is to just get the angle difference between the directions. I think there's a fairly recent thread about getting the angle between directions, actually, but whatever.

This here is code I just wrote off the top of my head, going at the problem from a slightly different angle.
//  Warning: Untested code!

proc/turn_towards(a, b, rotation = 45)
    if(a == b) return b
    if(a == turn(b, 180)) return pick(-rotation, rotation)
    return turn(a, clamp_angle(dir2angle(b) - dir2angle(a)) > 180 ? rotation : -rotation)


//  and from the Standard Kaiochao Library (in his mind)...

proc/clamp_angle(a)
    //  could be improved with modulo
    while(a <    0) a += 360
    while(a >= 360) a -= 360
    return a

proc/dir2angle(d)
    var global/d2a[] = list(0, 180, 0, 90, 45, 135, 0, 280, 315, 225)
    return (d in 1 to d2a.len) && d2a[d]
Aug 30 2013, 2:25 pm
In response to Kaiochao
Kaiochao wrote:
...

But it makes so little sense to have your dir2angle go clockwise from north (i.e. north = 0, east = 90, ...) when turn() rotates anticlockwise.
Aug 30 2013, 2:48 pm
In response to Toadfish
Sorry, I've just been used to clockwise rotations because of turn(icon, angle) and icon.Turn(angle). Darn BYOND inconsistencies. When I first posted this, I had the negative sign on the other "rotation", and then I realized that turn(dir, angle) did counter-clockwise rotations, so I switched them.
Aug 30 2013, 3:48 pm (Edited on Aug 30 2013, 3:55 pm)
I've just been used to clockwise rotations because of turn(icon, angle) and icon.Turn(angle).

Oh man. And you can't go about fixing that inconsistency because of backwards compatibility issues, at least not easily.
Sep 4 2013, 9:42 pm (Edited by moderator on Sep 4 2013, 10:35 pm)
I think you can fix that by doing it anticlockwise. It might get worked if you tried to do it.