I've been trying to implement the Moller-Trumbore ray-triangle intersection algorithm in my raytracing code. The code is supposed to read in a mesh and light sources, fire off rays from the light source, and return the triangle from the mesh which each ray intersects. Here is my implementation of the algorithm:
//Moller-Trumbore intersection algorithm void getFaceIntersect(modelStruct m, ray r, hitFaceStruct& hitFaces) { // Constant thoughout loop point origin = r.p0; point direction = r.u; hitFaces.isHit = false; for (int i = 0; i < m.faces; i++) { // Get face vertices point v1 = m.vertList[m.faceList[i].v1]; point v2 = m.vertList[m.faceList[i].v2]; point v3 = m.vertList[m.faceList[i].v3]; // Get two edgess point edge1 = v2 - v1; point edge2 = v3 - v1; // Get p point p = direction.cross(direction, edge2); // Use p to find determinant double det = p.dot(edge1, p); // If the determinant is about 0, the ray lies in the plane of the triangle if (abs(det) < 0.00000000001) { continue; } double inverseDet = 1 / det; point v1ToOrigin = (origin - v1); double u = v1ToOrigin.dot(v1ToOrigin, p) * inverseDet; // If u is not between 0 and 1, no hit if (u < 0 || u > 1) { continue; } // Used for calculating v point q = v1ToOrigin.cross(v1ToOrigin, edge1); double v = direction.dot(direction, q) * inverseDet; if (v < 0 || (u + v) > 1) { continue; } double t = q.dot(edge2, q) * inverseDet; // gets closest face if (t < abs(hitFaces.s)) { hitFaceStruct goodStruct = hitFaceStruct(); goodStruct.face = i; goodStruct.hitPoint = p; goodStruct.isHit = true; goodStruct.s = t; hitFaces = goodStruct; break; } } } The relevant code for hitFaceStruct and modelStruct is as follows:
typedef struct _hitFaceStruct { int face; //the index of the sphere in question in the list of faces float s; //the distance from the ray that hit it bool isHit; point hitPoint; } hitFaceStruct; typedef struct _modelStruct { char *fileName; float scale; float rot_x, rot_y, rot_z; float x, y, z; float r_amb, g_amb, b_amb; float r_dif, g_dif, b_dif; float r_spec, g_spec, b_spec; float k_amb, k_dif, k_spec, k_reflective, k_refractive; float spec_exp, index_refraction; int verts, faces, norms = 0; // Number of vertices, faces, normals, and spheres in the system point *vertList, *normList; // Vertex and Normal Lists faceStruct *faceList; // Face List } modelStruct; Whenever I shoot a ray, the values of u or v in the algorithm code always come out to a large negative number, rather than the expected small, positive one. The direction vector of the ray is normalized before I pass it on to the intersection code, and I'm positive I'm firing rays that would normally hit the mesh. Can anyone please help me spot my error here?
