htrdr

commit aad22b4ed34c01c7ef751c8446cc1a33773a513b
parent 3b41b51414d6c35391566df8b2473fbd83b7bd25
Author: Vincent Forest <vincent.forest@meso-star.com>
Date:   Wed, 14 Oct 2020 13:26:55 +0200

Small upd of the reject sampling on the rectangle sensor

Diffstat:
M
src/htrdr_sensor.c
 | 
39
+++++++++++++++++++++------------------

1 file changed, 21 insertions(+), 18 deletions(-)
diff --git a/src/htrdr_sensor.c b/src/htrdr_sensor.c
@@ -62,7 +62,6 @@ sample_rectangle_ray
 {
   struct s3d_hit hit = S3D_HIT_NULL;
   double pix_samp[2];
-  double up_dir[3] = {0, 0, 1};
   const double range[2] = {0, INF};
   double normal[3];
   ASSERT(rect && ground && ipix && pix_sz && rng && ray_org && ray_dir);
@@ -74,33 +73,37 @@ sample_rectangle_ray
   /* Retrieve the world space position of pix_samp */
   htrdr_rectangle_sample_pos(rect, pix_samp, ray_org);
 
-  /* Check that `ray_org' is not included into a geometry. Right now, use a
-   * naïve "up" intersection. */
-  HTRDR(ground_trace_ray(ground, ray_org, up_dir, range, NULL, &hit));
+  /* Sample a ray direction */
+  htrdr_rectangle_get_normal(rect, normal);
+  ssp_ran_hemisphere_cos(rng, normal, ray_dir, NULL);
 
-  /* Up direction is occluded, check if the sample must be recjected */
+  /* Check that `ray_org' is not included into a geometry */
+  HTRDR(ground_trace_ray(ground, ray_org, ray_dir, range, NULL, &hit));
+
+  /* Up direction is occluded. Check if the sample must be rejected, i.e. does it
+   * lies inside a geometry? */
   if(!S3D_HIT_NONE(&hit)) {
     struct htrdr_interface interf = HTRDR_INTERFACE_NULL;
     const struct mrumtl* mat = NULL;
+    float N[3]; /* Normalized normal of the hit */
     float wi[3];
-    float N[3];
-
-    /* Fetch the interface of the hit */
-    htrdr_ground_get_interface(ground, &hit, &interf);
+    float cos_wi_N;
 
-    /* Retrieve the material on the side of the incident direction */
-    f3_set_d3(wi, up_dir);
+    /* Compute the cosine between the incident ray direction and the hit normal */
+    f3_set_d3(wi, ray_dir);
     f3_normalize(N, hit.normal);
-    mat = f3_dot(wi, N) < 0 ? interf.mtl_front : interf.mtl_back;
+    cos_wi_N = f3_dot(wi, N);
 
-    /* Mat is NULL only for the external air. Reject the sample if the material
-     * is not null, i.e. the incident direction travels into the geometry */
+    /* Fetch the hit interface and retrieve the material into which the ray was
+     * traced */
+    htrdr_ground_get_interface(ground, &hit, &interf);
+    mat = cos_wi_N ? interf.mtl_front : interf.mtl_back;
+
+    /* Reject the sample if the material is not null, i.e. the incident
+     * direction do not travel into the external air and thus the challenged
+     * position is not outside */
     if(mat != NULL) return RES_BAD_OP;
   }
-
-  /* Sample a ray direction */
-  htrdr_rectangle_get_normal(rect, normal);
-  ssp_ran_hemisphere_cos(rng, normal, ray_dir, NULL);
   return RES_OK;
 }