graphics - How to get the intersection point? Ray Triangle Intersection C++ -

i intersection point on triangle when ray go through it. followed on line tutorial , made function, not correct coordinates of intersection point.

for example, should intersection point (0, 3, -1), if use ray origin (0, 2, -1), ray direction (0, 1, 0), triangle vertices p0 (0, 3, 0), p1 (-0.5, 3, -1), p2 (0.5, 3, -1). however, have got intersection point (0, 7, -1), not correct.

i appreciate time , help. :-)

float kepsilon = 0.000001;  v3f crossproduct(v3f point1, v3f point2){    v3f vector;     vector.x = point1.y * point2.z - point2.y * point1.z;    vector.y = point2.x * point1.z - point1.x * point2.z;    vector.z = point1.x * point2.y - point1.y * point2.x;     return vector; }  float dotproduct(v3f dot1, v3f dot2){    float dot = dot1.x * dot2.x + dot1.y * dot2.y + dot1.z * dot2.z;     return dot; }  //orig: ray origin, dir: ray direction, triangle vertices: p0, p1, p2.   bool raytriangleintersect(v3f orig, v3f dir, v3f p0, v3f p1, v3f p2){   // compute plane's normal    v3f p0p1, p0p2;    p0p1.x = p1.x - p0.x;    p0p1.y = p1.y - p0.y;    p0p1.z = p1.z - p0.z;     p0p2.x = p2.x - p0.x;   p0p2.y = p2.y - p0.y;    p0p2.z = p2.z - p0.z;    // no need normalize   v3f n = crossproduct(p0p1, p0p2); // n     // step 1: finding p    // check if ray , plane parallel ?   float ndotraydirection = dotproduct(n, dir); // if result 0, function return value false (no intersection).    if (fabs(ndotraydirection) < kepsilon){ // 0         return false; // parallel don't intersect !    }    // compute d parameter using equation 2   float d = dotproduct(n, p0);     // compute t (equation p=o+tr p intersection point ray origin o , direction r)    float t = (dotproduct(n, orig) + d) / ndotraydirection;     // check if triangle in behind ray   //if (t < 0){ return false; } // triangle behind     // compute intersection point using equation   v3f p;     //this part should work, not work.   p.x = orig.x + t * dir.x;    p.y = orig.y + t * dir.y;    p.z = orig.z + t * dir.z;      // step 2: inside-outside test   v3f c; // vector perpendicular triangle's plane     // edge 0   v3f edge0;     edge0.x = p1.x - p0.x;   edge0.y = p1.y - p0.y;   edge0.z = p1.z - p0.z;    v3f vp0;     vp0.x = p.x - p0.x;   vp0.y = p.y - p0.y;    vp0.z = p.z - p0.z;     c = crossproduct(edge0, vp0);     if (dotproduct(n, c) < 0) { return false; }// p on right side     // edge 1   v3f edge1;    edge1.x = p2.x - p1.x;   edge1.y = p2.y - p1.y;   edge1.z = p2.z - p1.z;    v3f vp1;     vp1.x = p.x - p1.x;    vp1.y = p.y - p1.y;    vp1.z = p.z - p1.z;     c = crossproduct(edge1, vp1);     if (dotproduct(n, c) < 0) { return false; } // p on right side     // edge 2   v3f edge2;    edge2.x = p0.x - p2.x;       edge2.y = p0.y - p2.y;   edge2.z = p0.z - p2.z;    v3f vp2;     vp2.x = p.x - p2.x;   vp2.y = p.y - p2.y;   vp2.z = p.z - p2.z;    c = crossproduct(edge2, vp2);    if (dotproduct(n, c) < 0) { return false; } // p on right side;     return true; // ray hits triangle  }  

thanks help.

you got t=5 , got (0,7,-1) correct number t 1 , reason have float t = (dotproduct(n, orig) + d) / ndotraydirection; while correct code float t = -((dotproduct(n, orig) - d) / ndotraydirection); solve problem hopefully.