Cleanup: CacheFile, use double precision for time

Both the Alembic and USD libraries use double precision floating
point numbers internally to store time. However the Alembic I/O
code defaulted to floats even though Blender's Scene FPS, which is
generally used for look ups, is stored using a double type. Such
downcasts could lead to imprecise lookups, and would cause
compilation warnings (at least on MSVC).

This modifies the Alembic exporter and importer to make use of
doubles for the current scene time, and only downcasting to float
at the very last steps (e.g. for vertex interpolation). For the
importer, doubles are also used for computing interpolation weights,
as it is based on a time offset.

Although the USD code already used doubles internally, floats were used
at the C API level. Those were replaced as well.

Differential Revision: https://developer.blender.org/D13855

3 files changed, 7 insertions, 7 deletions

diff --git a/source/blender/blenkernel/BKE_cachefile.h b/source/blender/blenkernel/BKE_cachefile.h
index 41a0ad3f763..fd559abf7f2 100644
--- a/source/blender/blenkernel/BKE_cachefile.h
+++ b/source/blender/blenkernel/BKE_cachefile.h
@@ -35,7 +35,7 @@ bool BKE_cachefile_filepath_get(const struct Main *bmain,
                                 const struct CacheFile *cache_file,
                                 char r_filename[1024]);
 
-float BKE_cachefile_time_offset(const struct CacheFile *cache_file, float time, float fps);
+double BKE_cachefile_time_offset(const struct CacheFile *cache_file, double time, double fps);
 
 /* Modifiers and constraints open and free readers through these. */
 void BKE_cachefile_reader_open(struct CacheFile *cache_file,
diff --git a/source/blender/blenkernel/intern/cachefile.c b/source/blender/blenkernel/intern/cachefile.c
index 338c74d550c..6b6b7223a0b 100644
--- a/source/blender/blenkernel/intern/cachefile.c
+++ b/source/blender/blenkernel/intern/cachefile.c
@@ -395,8 +395,8 @@ bool BKE_cachefile_filepath_get(const Main *bmain,
   if (cache_file->is_sequence && BLI_path_frame_get(r_filepath, &fframe, &frame_len)) {
     Scene *scene = DEG_get_evaluated_scene(depsgraph);
     const float ctime = BKE_scene_ctime_get(scene);
-    const float fps = (((double)scene->r.frs_sec) / (double)scene->r.frs_sec_base);
-    const float frame = BKE_cachefile_time_offset(cache_file, ctime, fps);
+    const double fps = (((double)scene->r.frs_sec) / (double)scene->r.frs_sec_base);
+    const int frame = (int)BKE_cachefile_time_offset(cache_file, (double)ctime, fps);
 
     char ext[32];
     BLI_path_frame_strip(r_filepath, ext);
@@ -410,10 +410,10 @@ bool BKE_cachefile_filepath_get(const Main *bmain,
   return true;
 }
 
-float BKE_cachefile_time_offset(const CacheFile *cache_file, const float time, const float fps)
+double BKE_cachefile_time_offset(const CacheFile *cache_file, const double time, const double fps)
 {
-  const float time_offset = cache_file->frame_offset / fps;
-  const float frame = (cache_file->override_frame ? cache_file->frame : time);
+  const double time_offset = (double)cache_file->frame_offset / fps;
+  const double frame = (cache_file->override_frame ? (double)cache_file->frame : time);
   return cache_file->is_sequence ? frame : frame / fps - time_offset;
 }
 
diff --git a/source/blender/blenkernel/intern/constraint.c b/source/blender/blenkernel/intern/constraint.c
index fc3f84778f8..0bab3d826fd 100644
--- a/source/blender/blenkernel/intern/constraint.c
+++ b/source/blender/blenkernel/intern/constraint.c
@@ -5417,7 +5417,7 @@ static void transformcache_evaluate(bConstraint *con, bConstraintOb *cob, ListBa
   }
 
   const float frame = DEG_get_ctime(cob->depsgraph);
-  const float time = BKE_cachefile_time_offset(cache_file, frame, FPS);
+  const double time = BKE_cachefile_time_offset(cache_file, (double)frame, FPS);
 
   if (!data->reader || !STREQ(data->reader_object_path, data->object_path)) {
     STRNCPY(data->reader_object_path, data->object_path);