Function isInsideTriangle

plugin/seq/plotPDF.cpp:2056–2079

	    st << "c\n";
	}
	st << "S\n";
    } // k
    return;
}

bool isInsideTriangle( const double px, const double py, const double *const vx, const double *const vy )
{
    // Find a, b \in \Real such that [px;py]-v0 =  a (v1-v0) + b (v2-v0).
    // if (0 < a < 1) && (0 < b < 1) && (0 < a+b < 1), then p is inside triangle v0--v1--v2

    // solve (v1x-v0x) * a + (v2x-v0x) * b = px-v0x
    //       (v1y-v0y) * a + (v2y-v0y) * b = py-v0y
    const double EPS = 1e-10;
    const double m00 = vx[1] - vx[0];
    const double m01 = vx[2] - vx[0];
    const double rhs0 = px - vx[0];

    const double m10 = vy[1] - vy[0];
    const double m11 = vy[2] - vy[0];
    const double rhs1 = py - vy[0];

    const double det = m00*m11 - m01*m10;
    assert( fabs(det) > EPS );

    const double a = ( m11 * rhs0 - m01 * rhs1) / det;
    const double b = (-m10 * rhs0 + m00 * rhs1) / det;