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

1 files changed, 8 insertions, 6 deletions

diff --git a/source/blender/io/alembic/intern/abc_reader_object.cc b/source/blender/io/alembic/intern/abc_reader_object.cc
index dac0890e7c5..a698eeca8f1 100644
--- a/source/blender/io/alembic/intern/abc_reader_object.cc
+++ b/source/blender/io/alembic/intern/abc_reader_object.cc
@@ -97,7 +97,9 @@ void AbcObjectReader::object(Object *ob)
   m_object = ob;
 }
 
-static Imath::M44d blend_matrices(const Imath::M44d &m0, const Imath::M44d &m1, const float weight)
+static Imath::M44d blend_matrices(const Imath::M44d &m0,
+                                  const Imath::M44d &m1,
+                                  const double weight)
 {
   float mat0[4][4], mat1[4][4], ret[4][4];
 
@@ -108,16 +110,16 @@ static Imath::M44d blend_matrices(const Imath::M44d &m0, const Imath::M44d &m1,
 
   convert_matrix_datatype(m0, mat0);
   convert_matrix_datatype(m1, mat1);
-  interp_m4_m4m4(ret, mat0, mat1, weight);
+  interp_m4_m4m4(ret, mat0, mat1, static_cast<float>(weight));
   return convert_matrix_datatype(ret);
 }
 
-Imath::M44d get_matrix(const IXformSchema &schema, const float time)
+Imath::M44d get_matrix(const IXformSchema &schema, const chrono_t time)
 {
   Alembic::AbcGeom::index_t i0, i1;
   Alembic::AbcGeom::XformSample s0, s1;
 
-  const float weight = get_weight_and_index(
+  const double weight = get_weight_and_index(
       time, schema.getTimeSampling(), schema.getNumSamples(), i0, i1);
 
   schema.get(s0, Alembic::AbcGeom::ISampleSelector(i0));
@@ -148,7 +150,7 @@ bool AbcObjectReader::topology_changed(const Mesh * /*existing_mesh*/,
   return false;
 }
 
-void AbcObjectReader::setupObjectTransform(const float time)
+void AbcObjectReader::setupObjectTransform(const chrono_t time)
 {
   bool is_constant = false;
   float transform_from_alembic[4][4];
@@ -214,7 +216,7 @@ Alembic::AbcGeom::IXform AbcObjectReader::xform()
 }
 
 void AbcObjectReader::read_matrix(float r_mat[4][4] /* local matrix */,
-                                  const float time,
+                                  const chrono_t time,
                                   const float scale,
                                   bool &is_constant)
 {