WoWMathHelper.IsBehind() - misleading description of arcRadians.

[strix]

        //
        // Summary:
        //     Returns a boolean indicating whether you are behind a target. A parameter
        //     indicates the wideness of the cone used to test.
        //
        // Parameters:
        //   me:
        //     Position of me.
        //
        //   target:
        //     Position of target.
        //
        //   targetFacingRadians:
        //     Facing of target in radians.
        //
        //   arcRadians:
        //     The arc to test against in radians. PI is the default value.
        public static bool IsBehind(WoWPoint me, WoWPoint target, float targetFacingRadians, float arcRadians = 3.14159f);

Please add to documentation that arcRadians defines "in front" arc, not "in behind" arc.

Arrow - facing
Red - arcRadians cone you pass to function,
Green - where it returns true,


Tested it on Training Dummy moving around step by step in "walk mode" with PI*0.8 and PI*1.2.
First one had true/false border slightly in front and second slightly behind, exactly the other way you would expect it to work.
Obviously on first one i couldn't use Backstab, but it still returned true.


In extreme cases:
Right now when you want to check "exactly behind" with PI/6 arc (30 degrees) it will do exactly opposite and return true anytime you are not "exactly in front".
To actually check "exactly behind" you need to pass 2*PI - PI/6 - 330 degrees arc.

imo best way to "fix" the function would be adding clear statement in description.

 

[jim87]

PI is the default value for arcRadians, this should make you think that combining "isBehind" and "PI" means PI is exactly behind the target...

 

[strix]

PI is the default value for arcRadians, this should make you think that combining "isBehind" and "PI" means PI is exactly behind the target...

PI equals 180 degrees - whole behind area, 2*PI makes 360 degrees - right now is exactly behind, 0 makes it exactly in front.

You should have it on math


It's exactly the same for behind and facing function, while for behind more logical would be passing behind-cone, not facing-cone.

 

[jim87]

What about if you consider 0 as "orientation 0", thus where the WoWObject is facing, and thus making PI the opposite? Your drawing fails of objectivity: you're considerating an angle different than 0 (PI/2, or 90?) as "orientation zero", which is substantially subjective to your way of observing the usual trigonometric circle. But we usually start from 0, this is clearer if you see a sin or cos graph.

According to you if you want to stay on the right of the object, you should use arcRadians = 0: does it make sense?

 

[strix]

Is it really so hard to understand?


arcRadians is the arc with it's middle right in front of target (WoWUnit.Rotation)
meaning that half of it goes to left (WoWUnit.Rotation - (arcRadians/2))
and other half of it goes to right (WoWUnit.Rotation + (arcRadians/2))

Basically you're defining wideness of IsFacing cone in IsBehind function.

For IsBehind() the middle of arc should be placed exactly behind (WoWUnit.Rotation + Math.PI), so you would define the wideness of IsBehind cone in IsBehind function.