diff options
| -rw-r--r-- | libdimension/triangle.c | 37 |
1 files changed, 22 insertions, 15 deletions
diff --git a/libdimension/triangle.c b/libdimension/triangle.c index 8ae7629..0e6daf4 100644 --- a/libdimension/triangle.c +++ b/libdimension/triangle.c @@ -26,7 +26,7 @@ #include "dimension.h" typedef struct dmnsn_triangle_payload { - dmnsn_vector a, ab, ac, na, nab, nac, normal; + dmnsn_vector na, nab, nac; } dmnsn_triangle_payload; /** Triangle intersection callback. */ @@ -36,11 +36,10 @@ dmnsn_triangle_intersection_fn(const dmnsn_object *triangle, dmnsn_line l, { const dmnsn_triangle_payload *payload = triangle->ptr; - double den = -dmnsn_vector_dot(l.n, payload->normal); - dmnsn_vector ax0 = dmnsn_vector_sub(l.x0, payload->a); - double t = dmnsn_vector_dot(ax0, payload->normal)/den; - double u = -dmnsn_vector_dot(l.n, dmnsn_vector_cross(ax0, payload->ac))/den; - double v = -dmnsn_vector_dot(l.n, dmnsn_vector_cross(payload->ab, ax0))/den; + /* See the change of basis in dmnsn_new_triangle() */ + double t = -l.x0.z/l.n.z; + double u = l.x0.x + t*l.n.x; + double v = l.x0.y + t*l.n.y; if (t >= 0.0 && u >= 0.0 && v >= 0.0 && u + v <= 1.0) { intersection->t = t; intersection->normal = dmnsn_vector_add( @@ -73,21 +72,29 @@ dmnsn_new_triangle(dmnsn_vector a, dmnsn_vector b, dmnsn_vector c, nc = dmnsn_vector_normalized(nc); dmnsn_triangle_payload *payload = DMNSN_MALLOC(dmnsn_triangle_payload); - payload->a = a; - payload->na = na; - payload->ab = dmnsn_vector_sub(b, a); - payload->nab = dmnsn_vector_sub(nb, na); - payload->ac = dmnsn_vector_sub(c, a); - payload->nac = dmnsn_vector_sub(nc, na); - payload->normal = dmnsn_vector_cross(payload->ab, payload->ac); + payload->na = na; + payload->nab = dmnsn_vector_sub(nb, na); + payload->nac = dmnsn_vector_sub(nc, na); dmnsn_object *triangle = dmnsn_new_object(); triangle->ptr = payload; triangle->intersection_fn = dmnsn_triangle_intersection_fn; triangle->inside_fn = dmnsn_triangle_inside_fn; triangle->free_fn = dmnsn_free; - triangle->bounding_box.min = dmnsn_vector_min(dmnsn_vector_min(a, b), c); - triangle->bounding_box.max = dmnsn_vector_max(dmnsn_vector_max(a, b), c); + triangle->bounding_box.min = dmnsn_zero; + triangle->bounding_box.max = dmnsn_new_vector(1.0, 1.0, 0.0); + + /* + * Make a change-of-basis matrix + * + * The new vector space has corners at <0, 1, 0>, <0, 0, 1>, and 0, + * corresponding to the basis (ab, ac, ab X ac). + */ + dmnsn_vector ab = dmnsn_vector_sub(b, a); + dmnsn_vector ac = dmnsn_vector_sub(c, a); + dmnsn_vector normal = dmnsn_vector_cross(ab, ac); + triangle->intrinsic_trans = dmnsn_new_matrix4(ab, ac, normal, a); + return triangle; } |