Update geom.c

[dolfje]

The algorithm didn't work for the following 2 intersecting triangles:

float triangle1_pts[3][3]={{0,1000,0},{0,1000,1000},{1000,1000,1000}};
float triangle1_norm[3];
getNormal(triangle1_pts[0],triangle1_pts[1],triangle1_pts[2],triangle1_norm);
struct FACE* triangle1=makePolygonFace(3,triangle1_norm,triangle1_pts);

float triangle2_pts[3][3]={{375,775,625},{375,1025,625},{625,1025,625}};	
float triangle2_norm[3];
getNormal(triangle2_pts[0],triangle2_pts[1],triangle2_pts[2],triangle2_norm);
struct FACE* triangle2=makePolygonFace(3,triangle2_norm,triangle2_pts);

result=classifyTriangleIntersect(triangle1,triangle2);
printf("Triangle1-Triangle2 Intersection Test Result: %d\n",result);
if (result)
	triangleIntersectionPoints(triangle1,triangle2);

[dolfje]

Another fix:

From in the paper:
Let i,j,k,l be the intersection points of L with edges p1 r1, p1 q1, p2 q2, p2 r2

Also gives an accurate intersection line for
triangle1: x: 0, y: 1000, z: 0 x: 0, y: 1000, z: 1000 x: 1000, y: 1000, z: 1000
triangle2: x: 375, y: 775, z: 375 x: 375, y: 1025, z: 375 x: 625, y: 1025, z: 375

[dolfje]

Swapping and rotating cannot be done at the same time. As you didn't put vertex 0 correct on the face2 yet, you cannot be sure to swap 1 and 2.