Purple contours? How doooo they do it?

Not sure if this is where to post it.... whatever.

I've noticed in KAG beta, when you select certain objects in the game, a purple outline appears around the object.
Like this:


I would like to ask the devs and anyone else who might know, how is this effect achieved? How do you put a contour line on an image like that?

EDIT: wrong prefix for this thread. Just realised what "Forum" means. Oh well. //fixed

 

Hello Xlayer,

I really like that visual effect so I played a little bit in Photoshop with blending modes. This is probably not the correct way and it seems to me if you want to achieve something like that, then it's going to be way more advanced. Anyway, here's what I made and if you got Photoshop, then you can see what I did. The answer probably lies somewhere there. (Edit: Noticed that the line is outwards, lmao.. my bad)

http://www.speedyshare.com/6dV7n/example.psd

 

omg thank you, this looks like not only the answer, but 3 answers! What kind of shader would be used? Or should I just learn how shaders work?

 

It seems to me that:

Since the outline color is purple (I have looked at the color in photoshop, and it is a very dark purple), that's where your purple highlight comes from. The blending mode used is add, and it seems to me that every pixel (at least on the edge) emits 4 pixels of the same color in the add blend mode, in the four cardinal directions like a cross. That would explain the brightness increase on the angled surfaces, the crosses of all the pixels overlap. That's just me though, I'm crazy.

 

Isn't this the wrong section to post this ?

 

Yes, it should be in King Arthurs Gold Beta Forums>Modding>Modding Help.
Though since it hasn't been moved yet, it probably isn't a big deal.