Elysian Shadows

Posted: **Sat Dec 13, 2008 3:00 pm**

i know there are probably hundreds of articles online, but sometimes its just better to try on your own.

i came up with this idea (though im sure it was thought of 100's of years ago by someone with a funny last name)
you have the normals of each line, and if the point to the normal vector and the normal vector have a angle greater than 90 degrees between them they point is out side of the triangle. this method is computation heavy so if anyone had other ideas let me know.

this algo can be sped up quite alot by tabulating the trig functions.

Posted: **Sat Dec 13, 2008 3:03 pm**

you could also see if the point lies in between pie slices <ACB and <CAB, if both are true then the point is in the triangle.

Posted: **Sun Dec 14, 2008 4:08 am**

What about the point to polygon method I used..? The one with vector cross product checking? http://elysianshadows.com/phpBB3/viewto ... art=999999

It can also be used for triangles (because it works for any convex polygon).

Posted: **Mon Dec 15, 2008 12:17 pm**

Code: Select all

    int side_of_line(Vec2 &a, Vec2 &b, Vec2 &p)
    {
       return float(p.y - a.y) * float(b.x - a.x) - float(p.x - a.x) * float(b.y - a.y);
    }

    bool point_inside_poly(std::vector<Vec2> &poly, Vec2 &point)
    {
       for(int i = 0; i < poly.size()-1; i++)
       {
          if(side_of_line(poly[i], poly[i+1], point) > 0)
             return false;

       }
       if(side_of_line(poly[poly.size()-1], poly[0], point) > 0)
             return false;
       return true;
    }

Elysian Shadows

anyone got an idea for point in triangle code?

anyone got an idea for point in triangle code?

Re: anyone got an idea for point in triangle code?

Re: anyone got an idea for point in triangle code?

Re: anyone got an idea for point in triangle code?