public static bool TriangleLineSegmentIntersect3d(Triangle3d t, xyz d, xyz e, out xyz pt1, out xyz pt2, int sign_d, int sign_e)
{
if (
(sign_d > 0) &&
(sign_e > 0)
)
{
pt1 = null;
pt2 = null;
return(false);
}
if (
(sign_d < 0) &&
(sign_e < 0)
)
{
pt1 = null;
pt2 = null;
return(false);
}
if (
(sign_d == 0) &&
(sign_e == 0)
)
{
// the segment is in the same plane as the triangle
// convert everything to 2d
Triangle2d t2d = t.ConvertTo2d();
xy d2 = ut.ConvertPointTo2d(d, t.a, t.iv, t.jv);
xy e2 = ut.ConvertPointTo2d(e, t.a, t.iv, t.jv);
bool bd = t2d.PointInside(d2);
bool be = t2d.PointInside(e2);
if (bd && be)
{
pt1 = d;
pt2 = e;
return(true);
}
else
{
xy w1;
xy w2;
bool bresult = t2d.SegmentIntersection(d2, e2, out w1, out w2);
if (bresult)
{
pt1 = ut.Convert2dPointTo3d(w1, t.a, t.iv, t.jv);
if (w2 != null)
{
pt2 = ut.Convert2dPointTo3d(w2, t.a, t.iv, t.jv);
}
else
{
pt2 = null;
}
}
else
{
pt1 = null;
pt2 = null;
}
return(bresult);
}
}
else
{
// the segment intersects the plane in only one point, so pt2 will be null
pt2 = null;
xyz p;
if (sign_d == 0)
{
p = d;
}
else if (sign_e == 0)
{
p = e;
}
else
{
// find the point where the pp_segment intersects the plane
double u = xyz.dotsub(t.n, t.a, d) / xyz.dotsub(t.n, e, d);
p = (e - d).multiply_in_place(u).add_in_place(d);
}
Triangle2d t2d = t.ConvertTo2d();
xy ipt = ut.ConvertPointTo2d(p, t.a, t.iv, t.jv);
bool b = t2d.PointInside(ipt);
if (b)
{
pt1 = p.copy();
}
else
{
pt1 = null;
}
return(b);
}
}
public static TriangleIntersection3d CalcTriangleIntersection3d_NotCoplanar(Triangle3d t1, Triangle3d t2)
{
int sign_t2_a = t1.GetSide(t2.a);
int sign_t2_b = t1.GetSide(t2.b);
int sign_t2_c = t1.GetSide(t2.c);
int sign_t1_a = t2.GetSide(t1.a);
int sign_t1_b = t2.GetSide(t1.b);
int sign_t1_c = t2.GetSide(t1.c);
TriangleIntersection3d ti = new TriangleIntersection3d();
if (!((sign_t2_a == sign_t2_b) && (sign_t2_b == sign_t2_c)))
{
xyz pt1;
xyz pt2;
if ((sign_t2_a != sign_t2_b) && TriangleLineSegmentIntersect3d(t1, t2.a, t2.b, out pt1, out pt2, sign_t2_a, sign_t2_b))
{
ti.Add(pt1);
ti.Add(pt2);
}
if ((sign_t2_b != sign_t2_c) && TriangleLineSegmentIntersect3d(t1, t2.b, t2.c, out pt1, out pt2, sign_t2_b, sign_t2_c))
{
ti.Add(pt1);
ti.Add(pt2);
}
if ((sign_t2_c != sign_t2_a) && TriangleLineSegmentIntersect3d(t1, t2.c, t2.a, out pt1, out pt2, sign_t2_c, sign_t2_a))
{
ti.Add(pt1);
ti.Add(pt2);
}
if ((sign_t1_a != sign_t1_b) && TriangleLineSegmentIntersect3d(t2, t1.a, t1.b, out pt1, out pt2, sign_t1_a, sign_t1_b))
{
ti.Add(pt1);
ti.Add(pt2);
}
if ((sign_t1_b != sign_t1_c) && TriangleLineSegmentIntersect3d(t2, t1.b, t1.c, out pt1, out pt2, sign_t1_b, sign_t1_c))
{
ti.Add(pt1);
ti.Add(pt2);
}
if ((sign_t1_c != sign_t1_a) && TriangleLineSegmentIntersect3d(t2, t1.c, t1.a, out pt1, out pt2, sign_t1_c, sign_t1_a))
{
ti.Add(pt1);
ti.Add(pt2);
}
}
return(ti);
}
public static TriangleIntersection3d CalcTriangleIntersection3d(Triangle3d t1, Triangle3d t2)
{
if (ut.AllVerticesPlanar(t1, t2))
{
TriangleIntersection3d ti = new TriangleIntersection3d();
xyz n = t1.n;
xyz i = t1.iv;
xyz j = t1.jv;
xy a1 = ut.ConvertPointTo2d(t1.a, t1.a, i, j);
xy b1 = ut.ConvertPointTo2d(t1.b, t1.a, i, j);
xy c1 = ut.ConvertPointTo2d(t1.c, t1.a, i, j);
xy a2 = ut.ConvertPointTo2d(t2.a, t1.a, i, j);
xy b2 = ut.ConvertPointTo2d(t2.b, t1.a, i, j);
xy c2 = ut.ConvertPointTo2d(t2.c, t1.a, i, j);
TriangleIntersection2d ti2d = TriangleIntersection2d.CalcTriangleIntersection2d(a1, b1, c1, a2, b2, c2);
if (ti2d.Count > 0)
{
foreach (xy p in ti2d)
{
xyz q = ut.Convert2dPointTo3d(p, t1.a, i, j);
ti.Add(q);
}
}
return(ti);
}
else
{
return(CalcTriangleIntersection3d_NotCoplanar(t1, t2));
}
}
