Point in Triangle?

[TheBlob]

Hi!
Well, my problem is the following:
I have a point p(x|y) and three points a,b,c forming a triangle. How can I check, if the point p is in the triangle??
Maybe someone has a good, working function?
Please help!
TheBlob!

[Leyder Dylan]

Here's a link.
http://www.gametutorials.com/Tutoria...OpenGL_Pg2.htm

"Polygon Detection"

It's works !

Yeah !!!!!!!!!!!!!!!

[Iceman]

I have exactly what u need ...

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// Determine if a two dimensional point lies within the confines of a given
// two dimensional triangle.
//
// From Dr. Dobbs Journal, October, 2000
 
bool IsPointInsideFace(
		double pX,
		double pY,
		double v0x,
		double v0y,
		double v1x,
		double v1y,
		double v2x,
		double v2y
	)
{
    double x0, x1, x2, y1, u, v, denom;
    x1 = v1x - v0x;
 
    if ( x1 == 0.0 )
	{
        // Triangle points 0 and 1 have the same X value
 
        // Zero area test - can be removed if triangle is known to be valid
		x2 = v2x - v0x;
        if ( ( x2 == 0.0 ) | |
 
            // Compute u and check bounds
            ( ( u = (pX - v0x) / x2 ) < 0.0 ) &amp;#0124; &amp;#0124;
            ( u > 1.0 ) &amp;#0124; &amp;#0124;
 
            // Zero area test - remove if known to be valid
            ( ( y1 = v1y - v0y ) == 0.0 ) &amp;#0124; &amp;#0124;
 
            // Compute v and check bounds
            ( ( v = ( (pY - v0y) - u *
                ( v2y - v0y ) ) / y1 ) < 0.0 ) )
		{
 
                // Missed for some reason
                return false;
        }
 
    }
	else
	{
        // Triangle points 0 and 1 have a different X value
        // Compute denom and check for zero area triangle - check
		// is not needed if triangle known to be valid.
        x2 = v2x - v0x;
        y1 = v1y - v0y;
        denom = ( v2y - v0y ) * x1 - x2 * y1;
        if ( ( denom == 0.0 ) &amp;#0124; &amp;#0124;
 
            // Compute u and check bounds
            ( ( u = ( (pY - v0y) * x1 - (x0 = pX - v0x) * y1 ) / denom ) < 0.0 ) &amp;#0124; &amp;#0124;
            ( u > 1.0 ) &amp;#0124; &amp;#0124;
 
            // Compute v & check bounds
            ( ( v = ( x0 - u * x2 ) / x1 ) < 0.0 ) )
		{
 
                // Missed for some reason
                return false;
        }
    }
 
    // Check gamma
    if ( u + v > 1.0 )
	{
        // Outside third edge
        return false;
    }
 
    return true;
}

[Lsea]

I have a simple method :
TEST the point P is in triangle ABC or not
add the area of PAB,PBC,PCA ,if the total is equal to the area of ABC ,then we know the point P is in the triangle ,otherwise is out.
right?

[Iceman]

Sure, but benchmark it against the above algorithm and I am willing to bet that it looses in terms of raw performance. If you get a chance to do so please post the results here ... thx