htrdr

commit 2ed9e2d029ab57811f294812b9abb2b6c271fd26
parent a6afdad1576ceb0ce47553399fbf259b25b6566a
Author: Vincent Forest <vincent.forest@meso-star.com>
Date:   Tue, 13 Oct 2020 11:38:58 +0200

Take into account very thin materials (e.g. leaves)

Diffstat:
M
src/htrdr_ground.c
 | 
26
+++++++++++++++++++++-----
M
src/htrdr_interface.c
 | 
39
+++++++++++++++++++++------------------
M
src/htrdr_interface.h
 | 
1
+

3 files changed, 43 insertions(+), 23 deletions(-)
diff --git a/src/htrdr_ground.c b/src/htrdr_ground.c
@@ -162,6 +162,7 @@ parse_shape_interface
 {
   struct str str;
   char* mtl_name_front = NULL;
+  char* mtl_name_thin = NULL;
   char* mtl_name_back = NULL;
   char* tk_ctx = NULL;
   res_T res = RES_OK;
@@ -181,7 +182,11 @@ parse_shape_interface
   /* Parse the name of the front/back faces */
   mtl_name_front = strtok_r(str_get(&str), ":", &tk_ctx);
   ASSERT(mtl_name_front); /* This can't be NULL */
+
+  /* Parse the back/thin material names */
+  mtl_name_thin = strtok_r(NULL, ":", &tk_ctx);
   mtl_name_back = strtok_r(NULL, ":", &tk_ctx);
+  if(!mtl_name_back) mtl_name_back = mtl_name_thin;
   if(!mtl_name_back) {
     htrdr_log_err(htrdr,
       "The material name of the shape back faces are missing `%s'.\n", name);
@@ -189,17 +194,28 @@ parse_shape_interface
     goto error;
   }
 
+  /* Fetch the interface material */
+  if(mtl_name_thin) {
+    interf->mtl_thin = htrdr_mtl_get(htrdr->mtl, mtl_name_thin);
+    if(!interf->mtl_thin) {
+      htrdr_log_err(htrdr,
+      "Invalid interface `%s:%s:%s'. "
+      "The material of the interface is unknown.\n",
+      mtl_name_front, mtl_name_thin, mtl_name_back);
+      res = RES_BAD_ARG;
+      goto error;
+    }
+  }
+
   /* Fetch the front/back materials */
   interf->mtl_front = htrdr_mtl_get(htrdr->mtl, mtl_name_front);
   interf->mtl_back = htrdr_mtl_get(htrdr->mtl, mtl_name_back);
-  if(!interf->mtl_front && !interf->mtl_back) {
-    htrdr_log_err(htrdr,
-      "Invalid interface `%s:%s'. "
-      "The front and the back materials are both uknown.\n",
-      mtl_name_front, mtl_name_back);
+  if(!interf->mtl_front && !interf->mtl_back && !interf->mtl_thin) {
+    htrdr_log_err(htrdr, "Invalid interface `%s'.\n", name);
     res = RES_BAD_ARG;
     goto error;
   }
+
 exit:
   str_release(&str);
   return res;
diff --git a/src/htrdr_interface.c b/src/htrdr_interface.c
@@ -123,33 +123,36 @@ htrdr_interface_create_bsdf
   res_T res = RES_OK;
   (void)pos;
   ASSERT(htrdr && pos && hit && out_bsdf);
-  ASSERT(interf && (interf->mtl_front || interf->mtl_back));
+  ASSERT(interf && (interf->mtl_front || interf->mtl_back || interf->mtl_thin));
 
   ASSERT(htrdr && interf && pos && dir && hit && out_bsdf);
   ASSERT(d3_is_normalized(dir));
 
-  d3_normalize(N, d3_set_f3(N, hit->normal));
+  if(interf->mtl_thin) {
+    mat = interf->mtl_thin;
+  } else {
+    d3_normalize(N, d3_set_f3(N, hit->normal));
+    hit_side = d3_dot(N, dir) < 0 ? FRONT : BACK;
 
-  hit_side = d3_dot(N, dir) < 0 ? FRONT : BACK;
-
-  /* Retrieve the brdf of the material on the other side of the hit side */
-  switch(hit_side) {
-    case BACK: mat = interf->mtl_front; break;
-    case FRONT: mat = interf->mtl_back; break;
-    default: FATAL("Unreachable code.\n");  break;
-  }
-
-  /* Due to numerical issue the hit side might be wrong and thus the fetched
-   * material might be undefined (e.g. semi-transparent materials). Handle this
-   * issue by fetching the other material. */
-  if(!mat) {
+    /* Retrieve the brdf of the material on the other side of the hit side */
     switch(hit_side) {
-      case BACK: mat = interf->mtl_back; break;
-      case FRONT: mat = interf->mtl_front; break;
+      case BACK: mat = interf->mtl_front; break;
+      case FRONT: mat = interf->mtl_back; break;
       default: FATAL("Unreachable code.\n");  break;
     }
+
+    /* Due to numerical issue the hit side might be wrong and thus the fetched
+     * material might be undefined (e.g. semi-transparent materials). Handle this
+     * issue by fetching the other material. */
+    if(!mat) {
+      switch(hit_side) {
+        case BACK: mat = interf->mtl_back; break;
+        case FRONT: mat = interf->mtl_front; break;
+        default: FATAL("Unreachable code.\n");  break;
+      }
+    }
+    ASSERT(mat);
   }
-  ASSERT(mat);
 
   r = ssp_rng_canonical(rng);
 
diff --git a/src/htrdr_interface.h b/src/htrdr_interface.h
@@ -28,6 +28,7 @@ struct ssp_rng;
 struct htrdr_interface {
   const struct mrumtl* mtl_front;
   const struct mrumtl* mtl_back;
+  const struct mrumtl* mtl_thin; /* != NULL <=> thin material */
 };
 static const struct htrdr_interface HTRDR_INTERFACE_NULL;