ray: misc computational fixups

ray:object intersection coordinates were incorrectly being computed
relative to the ray origin using a subtraction instead of addition, a
silly mistake with surprisingly acceptable results.  Those results
were a result of other minor complementary mistakes compensating to
produce reasonable looking results.

In the course of experimenting with an acceleration data structure it
became very apparent that 3d space traversal vectors were not behaving
as intended, leading to review and correction of this code.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/modules/ray/ray_object_plane.h b/src/modules/ray/ray_object_plane.h
index 490238c..0d3a51b 100644
--- a/src/modules/ray/ray_object_plane.h
+++ b/src/modules/ray/ray_object_plane.h
@@ -29,14 +29,14 @@ static inline int ray_object_plane_intersects_ray(ray_object_plane_t *plane, uns
 {
 	float	d = ray_3f_dot(&plane->normal, &ray->direction);
 
-	if (d >= 0.00001f) {
+	if (d < 0.0f) {
 		float	distance = plane->_prepared.primary_dot_plus;
 
 		if (depth)
 			distance = (ray_3f_dot(&plane->normal, &ray->origin) + plane->distance);
 
-		distance /= d;
-		if (distance > 0) {
+		distance /= -d;
+		if (distance > 0.0f) {
 			*res_distance = distance;
 
 			return 1;