star-2d

commit cb9250662cfae39b3dd67eb96442f3aa6e26e688
parent a3a432d64ee51109e30f871a2c6b9ba38572dbee
Author: Christophe Coustet <christophe.coustet@meso-star.com>
Date:   Thu, 14 Jan 2021 17:26:57 +0100

Performance improvement

Diffstat:
M
src/s2d_scene_view_closest_point.c
 | 
15
++++++++-------

1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/src/s2d_scene_view_closest_point.c b/src/s2d_scene_view_closest_point.c
@@ -53,29 +53,30 @@ closest_point_segment
    float* s) /* Parametric coordinate of the closest point onto [v0, v1] */
 {
   float v[2]; /* Vector from v0 to p */
-  float segment_len; /* Length of the [v0, v1] */
-  float dst; /* Dst from v0 to the orthogonal projection of p onto [v0, v1] */
+  float segment_len2; /* Square length of the [v0, v1] */
+  float dst_x_seglen; /* |p' v0| x |v0 v1|
+                       * p' is the orthogonal projection of p onto [v0, v1] */
   ASSERT(p && v0 && v1);
   ASSERT(f2_eq(f2_sub(v, v1, v0), E));
 
   /* Orthogonally project the point onto the segment */
   f2_sub(v, p, v0);
-  segment_len = f2_len(E);
-  dst = f2_dot(v, E) / segment_len;
+  dst_x_seglen = f2_dot(v, E);
 
   /* Check if the closest point is the segment vertex 'v0' */
-  if(dst <= 0) {
+  if(dst_x_seglen <= 0) {
     *s = 0;
     return f2_set(closest_pt, v0);
   }
   /* Check if the closest point is the segment vertex 'v1' */
-  if(dst >= segment_len) {
+  segment_len2 = f2_dot(E,E);
+  if(dst_x_seglen >= segment_len2) {
     *s = 1;
     return f2_set(closest_pt, v1);
   }
 
   /* The closest point is on the segment */
-  *s = dst / segment_len;
+  *s = dst_x_seglen / segment_len2;
   ASSERT(*s == CLAMP(*s, 0, 1));
   return f2_add(closest_pt, f2_mulf(closest_pt, E, *s), v0);
 }