Calculate surface angle

[Jin]

How do you calculate an angle of a point on a surface? A.S 2

[GustTheASGuy]

That depends on what the surface is. If it's a bitmap, you'll have to iterate the angle around your point to find two points on the border of the shape and get the normal of the line between them.

[Jin]

It's pre-drawn vectors in a movieclip.

[GustTheASGuy]

Which you can only access as a runtime bitmap unless you use Flashes JSAPI. In which case, get the normal of the segment you intersect?

[Jin]

I still don't get it. If I were to go with the bitmap method, should I specify an angle? Because there aren't any fixed values to access.

[GustTheASGuy]

What, no. You iterate points around the given in a circle to find two on the border of the shape and get their normal.

[Disarray-yarrasiD]

At 8/21/08 07:20 AM, GustTheASGuy wrote: What, no. You iterate points around the given in a circle to find two on the border of the shape and get their normal.

you test for collisions in a circle, for example every 10 degrees, and take the average angle of the two farthest border points.

//outline
for(var i=0;i<Math.PI*2, i+=Math.PI/10){
if(_root.ground.hitTest(_x+Math.cos(i)*1 0,_y+Math.sin(i)*10)){
//find border points
}
}
//find average angle