star-3d

commit fbf93f7580f99b673a76692cda7e933128ec937a
parent f6c419b3c33984c897daf8c26e02af288c5d1bda
Author: Vincent Forest <vincent.forest@meso-star.com>
Date:   Fri, 11 Jan 2019 14:43:00 +0100

Fix the s3d_scene_view_sample function

Diffstat:
M
src/s3d_scene_view.c
 | 
41
++++++++++++++++++++++++++++++++---------

1 file changed, 32 insertions(+), 9 deletions(-)
diff --git a/src/s3d_scene_view.c b/src/s3d_scene_view.c
@@ -1284,6 +1284,7 @@ s3d_scene_view_sample
   struct geometry** pgeom;
   struct geometry* geom;
   size_t sz;
+  size_t i;
   const struct fltui* fltui, *fltui_found;
   const float* flt, *flt_found;
   unsigned ishape;
@@ -1322,15 +1323,22 @@ s3d_scene_view_sample
   } else {
     fltui = darray_fltui_cdata_get(&scnview->cdf);
     sz = darray_fltui_size_get(&scnview->cdf);
-    f = u * fltui[sz-1].flt; /* Map u to the CDF bounds */
+    f = u * fltui[sz-1].flt; /* Map u to [0, SceneArea[ */
     fltui_found = search_lower_bound
       (&f, fltui, sz, sizeof(*fltui), cmp_float_to_fltui);
     ASSERT(fltui_found);
+
+    /* search_lower_bound returns the first entry that is not less than `f'.
+     * The following code discards entries that are also `equal' to `f' */
+    i = (size_t)(fltui_found - fltui);
+    while(fltui[i].flt == f && i < sz) ++i;
+    ASSERT(i < sz);
+
+    fltui_found = fltui + i;
     ishape = fltui_found->ui;
 
-    /* Transform u to the geometry CDF bounds */
-    if(fltui_found != fltui)
-      f -= fltui_found[-1].flt;
+    /* Map f to [0, <Shape|Instance>Area[ */
+    if(i) f -= fltui_found[-1].flt;
   }
   pgeom = htable_geom_find(&scnview->cached_geoms, &ishape);
   ASSERT(pgeom);
@@ -1353,12 +1361,19 @@ s3d_scene_view_sample
       sz = darray_fltui_size_get(&geom->data.instance->scnview->cdf);
       fltui_found = search_lower_bound
         (&f, fltui, sz, sizeof(*fltui), cmp_float_to_fltui);
-      ASSERT(fltui_found != NULL);
+      ASSERT(fltui_found);
+
+      /* search_lower_bound returns the first entry that is not less than `f'.
+       * The following code discards entries that are also `equal' to `f' */
+      i = (size_t)(fltui_found - fltui);
+      while(fltui[i].flt == f && i < sz) ++i;
+      ASSERT(i < sz);
+
+      fltui_found = fltui + i;
       ishape = fltui_found->ui;
 
-      /* Transform u to the geometry CDF bounds */
-      if(fltui_found != fltui)
-        f -= fltui_found[-1].flt;
+      /* Map `f' to [0, ShapeArea[ */
+      if(i) f -= fltui_found[-1].flt;
     }
     pgeom = htable_geom_find(&geom->data.instance->scnview->cached_geoms, &ishape);
     ASSERT(pgeom);
@@ -1376,7 +1391,15 @@ s3d_scene_view_sample
     sz = darray_float_size_get(&geom->data.mesh->cdf);
     flt_found = search_lower_bound(&f, flt, sz, sizeof(*flt), cmp_float);
     ASSERT(flt_found != NULL);
-    primitive->prim_id = (unsigned)(flt_found - flt);
+    i = (size_t)(flt_found - flt);
+
+    /* search_lower_bound returns the first entry that is not less than `f'.
+     * The following code discards entries that are also `equal' to `f' */
+    while(flt[i] == f && i < sz) ++i;
+    ASSERT(i < sz);
+
+    primitive->prim_id = (unsigned)i;
+
   } else {
     FATAL("Unreachable code\n");
   }