Compass/Tracker/Pointer

ID:1951751
 
Sep 30 2015, 11:26 am (Edited on Sep 30 2015, 3:36 pm)
(See the best response by Kaiochao.)
Problem description:



We have Bob.

Bob wants to find his enemies, though they're off screen. To assist Bob, I would like arrows pointing in their direction along with the arrows' screen_loc based on the directional orientation.

The arrows, I can turn. My only problem thus far is properly moving the arrow. What sort of formula would I use to adjust the offsets?

Help me help Bob!

Edit: Bob is happy!
Sep 30 2015, 11:55 am (Edited on Sep 30 2015, 12:12 pm)
Best response
Off the top of my head:
// library used: Kaiochao.AbsolutePositions
#include <kaiochao/absolutepositions/absolute positions/absolute positions.dme>

mob
    proc/PointArrow(obj/Arrow, atom/Target, MinDistance)
        // src: the player seeing the arrow
        // Arrow:  the arrow object in your HUD
        // Target: where you want the arrow to point
        // MinDistance: pixels before Target is considered "off screen"

        // default to slightly less than half the smallest size of the viewport
        if(isnull(MinDistance))
            MinDistance = min(client.bound_width, client.bound_height) * (3/8)

        // a vector (difference in positions) from src to Target, in pixels
        var dx = Target.Cx() - Cx()
        var dy = Target.Cy() - Cy()

        // the square magnitude of the vector
        var dot = dx*dx + dy*dy

        // the target is too close, hide the arrow and stop the proc
        if(dot < MinDistance * MinDistance)
            Arrow.screen_loc = null
            return

        // the target is far enough away at this point

        // get the angle to the target using atan2
        var angle = dx > 0 ? arccos(dy / sqrt(dot)) : -arccos(dy / sqrt(dot))

        // position the arrow in the center of the screen (will be offset by transform)
        Arrow.screen_loc = "CENTER"

        // start setting up the arrow's transform
        // imagine a clock
        // you start in the center
        // Translate(0, MinDistance) moves you straight up to the 12
        // Turn(angle) turns you clockwise to the angle, along the curved edge of the clock
        var matrix/m = new
        m.Translate(0, MinDistance)
        m.Turn(angle)
        Arrow.transform = m

        // and we're done

All you have to do is add an obj with the arrow's appearance to client.screen and call this proc whenever you want to update it. For example:
#include <kaiochao/shapes/shapes.dme>

world
    maxx = 50
    maxy = 50
    fps = 60

turf
    icon_state = "rect"
    New() color = x % 2 == y % 2 ? "silver" : "gray"

obj/arrow
    icon_state = "arrow"
    color = "red"

mob
    icon_state = "oval"
    color = "blue"
    step_size = 4
    var target_arrows[]

    Login()
        ..()
        new /mob/enemy (locate(10, 10, 1))

    verb/remove_target(mob/m in target_arrows)
        client.screen -= target_arrows[m]
        target_arrows -= m
        if(!target_arrows.len)
            target_arrows = null

mob/enemy
    color = "red"

    verb/add_target()
        set src in oview()
        if(src in usr.target_arrows)
            return
        if(!usr.target_arrows)
            usr.target_arrows = new
        usr.target_arrows[src] = new /obj/arrow
        usr.client.screen += usr.target_arrows[src]

        // update the arrow every frame
        while(usr && (src in usr.target_arrows))
            usr.PointArrow(usr.target_arrows[src], src)
            sleep world.tick_lag

You could even add to this demo a verb on the arrow that removes the target, but I've probably done enough already.
Sep 30 2015, 12:00 pm
In response to Kaiochao
 
if(isnull(MinDistance))
     MinDistance = min(client.bound_width, client.bound_height) * (3/8)


Where are you pulling the client's bound width and height variables from? They aren't native to .dm
Sep 30 2015, 12:14 pm
In response to Bl4ck Adam
They're new to 509, which is in beta. There are other ways to get this information, though.
// I already made a library that includes it
#include <kaiochao/mapinfo/map info/map info.dme>

// client.bound_width == client.ViewPixelWidth()
// client.bound_height == client.ViewPixelHeight()
Sep 30 2015, 12:36 pm
I went ahead and updated to the beta. The arrows work like a charm. Thanks!
Sep 30 2015, 12:39 pm
In response to Bl4ck Adam
Should I make this a library...? It's kind of simplistic, especially if you remove all the comments.
Sep 30 2015, 12:43 pm
I don't see why not. Many a game could probably use something of the sort, be it a quest tracker or anything they can think of in that case.
Sep 30 2015, 1:22 pm
There was a really old library that would put arrows on the edge of the map/view and you could move with those. I wasn't able to track it down though (it is really old and I don't remember what it was called).

Seems like kaio got it handled for you, though! :)
Sep 30 2015, 1:25 pm
In response to AERProductions
AERProductions wrote:
There was a really old library that would put arrows on the edge of the map/view and you could move with those. I wasn't able to track it down though (it is really old and I don't remember what it was called).

Seems like kaio got it handled for you, though! :)

This is what you're talking about!
Sep 30 2015, 1:26 pm
In response to Bl4ck Adam
Yes it is, thanks for reminding me!
That is what I was going to suggest, but it probably isn't optimal. :)
Sep 30 2015, 2:23 pm
In response to Bl4ck Adam
Bl4ck Adam wrote:
AERProductions wrote:
There was a really old library that would put arrows on the edge of the map/view and you could move with those. I wasn't able to track it down though (it is really old and I don't remember what it was called).

Seems like kaio got it handled for you, though! :)

This is what you're talking about!

Wow, I forgot all about that, it's from twelve years ago. Not what they were looking for though.
Sep 30 2015, 2:47 pm
In response to Kaiochao
Kaiochao wrote:
Should I make this a library...? It's kind of simplistic, especially if you remove all the comments.


Please do. I can see myself wanting this somewhere down the line
Sep 30 2015, 2:53 pm
In response to Flick
The magical things the years do, eh flick?

I remember messing around with that library all those years ago on a certain, unreleased project which was my first attempt at a game on byond. Still have the design docs for that project, but not the original source (lost to hdd damage).
Sep 30 2015, 2:57 pm
Here's the library. It's a bit updated and easier to include, compared to what's in the forum post.

http://www.byond.com/developer/Kaiochao/ScreenArrows
Sep 30 2015, 3:17 pm
In response to Kaiochao
Kaiochao wrote:
Here's the library. It's a bit updated and easier to include, compared to what's in the forum post.

http://www.byond.com/developer/Kaiochao/ScreenArrows

It looks a lot nicer both in game and code itself. You're the best!