Draw line to/from UISprite

[TieKei]

Hey there,

I'm new to NGUI, but I did some hours of research before posting.
My main goal is to draw a line to/from an UISprite, so I placed an UISprite and I'm able to draw Lines to Unity's GUI Layer via DrawLine Script (http://wiki.unity3d.com/index.php?title=DrawLine).

Now my problem is to find the exact screen-position of my UISprite to find the perfect startpoint for my drawLine.

My current approach:

1. // JS
2. var my_sprite:GameObject = NGUITools.AddChild(GameObject.Find("UI Root"), prefab_sprite); //adds a sprite from prefab
3. var ui_sprite:UISprite = gesture.GetComponent.<UISprite>();
4. var ui_camera = GameObject.Find("UI Camera").GetComponent.<Camera>()
5.    
6. ui_sprite.SetAnchor(target.transform); // target is a GameObject
7. ui_sprite.leftAnchor.absolute = -50; // wanted a 100 px sprite, centered on target
8. ui_sprite.rightAnchor.absolute = 50;
9. ui_sprite.ResetAnchors();
10.  
11.  
12. var ngui_pos:Vector3 = ui_camera.WorldToScreenPoint( ui_sprite.get_worldCenter() );
13.  
14. var screen_position:Vector2 = Vector2( parseInt(pos.x), Screen.height - parseInt(pos.y) );
15.  

I'm pretty sure there is a better way, but I wasn't able to find one.
At least it works for the y coordinate for every resolution I tested. x is always wrong though.

Thanks,
Tim

[TieKei]

so I found a working solution by ignoring the UISprite position completely and reverse engineer it's position by calculating it's anchor-target's position to screen-points and go from there.

1. var p = Main.camera.WorldToScreenPoint( target.transform.position );
2. var screen_position = Vector2( parseInt(p.x), Screen.height -parseInt(p.y))
3.  

Now I'm able to draw a line to/from the center of my UISprite.

I really don't understand why this has to be so ugly and complicated in Unity...
WorldToScreenPoint seems to return the correct x position (but as a float, which result in really strange positions if you don't parse it to Int before applying it to a Vector2). The y position however seems to be measured from the screens bottom (why would you even...)

Edit: my UI Camera messed up the whole process, with Main.camera it's working somewhat better, so the following rant is not appropriate anymore
but not enough, also it seems to be off by about Screen.height * 0.05 (this was the moment where I seriously thought about getting into wood-carving and never touch something awful like this again  )

[ArenMook]

Position in graphics is always based from the bottom-left corner. Think about it like drawing a graph... X and Y position -- both X and Y increase from 0.