Alembic: store a pointer to the object reader in the cache modifiers and

constraints.

This avoids traversing the archive everytime object data is needed and
gives an overall consistent ~2x speedup here with files containing
between 136 and 500 Alembic objects. Also this somewhat nicely de-
duplicates code between data creation (upon import) and data streaming
(modifiers and constraints).

The only worying part is what happens when a CacheFile is deleted and/or
has its path changed. For now, we traverse the whole scene and for each
object using the CacheFile we free the pointer and NULL-ify it (see
BKE_cachefile_clean), but at some point this should be re-considered and
make use of the dependency graph.

1 files changed, 52 insertions, 0 deletions

diff --git a/source/blender/alembic/intern/abc_curves.cc b/source/blender/alembic/intern/abc_curves.cc
index 2b54741a5c5..7e5ea3b1853 100644
--- a/source/blender/alembic/intern/abc_curves.cc
+++ b/source/blender/alembic/intern/abc_curves.cc
@@ -37,6 +37,7 @@ extern "C" {
 
 #include "BLI_listbase.h"
 
+#include "BKE_cdderivedmesh.h"
 #include "BKE_curve.h"
 #include "BKE_object.h"
 
@@ -353,3 +354,54 @@ void read_curve_sample(Curve *cu, const ICurvesSchema &schema, const float time)
 		BLI_addtail(BKE_curve_nurbs_get(cu), nu);
 	}
 }
+
+/* NOTE: Alembic only stores data about control points, but the DerivedMesh
+ * passed from the cache modifier contains the displist, which has more data
+ * than the control points, so to avoid corrupting the displist we modify the
+ * object directly and create a new DerivedMesh from that. Also we might need to
+ * create new or delete existing NURBS in the curve.
+ */
+DerivedMesh *AbcCurveReader::read_derivedmesh(DerivedMesh */*dm*/, const float time, int /*read_flag*/)
+{
+	ISampleSelector sample_sel(time);
+	const ICurvesSchema::Sample sample = m_curves_schema.getValue(sample_sel);
+
+	const P3fArraySamplePtr &positions = sample.getPositions();
+	const Int32ArraySamplePtr num_vertices = sample.getCurvesNumVertices();
+
+	int vertex_idx = 0;
+	int curve_idx = 0;
+	Curve *curve = static_cast<Curve *>(m_object->data);
+
+	const int curve_count = BLI_listbase_count(&curve->nurb);
+
+	if (curve_count != num_vertices->size()) {
+		BKE_nurbList_free(&curve->nurb);
+		read_curve_sample(curve, m_curves_schema, time);
+	}
+	else {
+		Nurb *nurbs = static_cast<Nurb *>(curve->nurb.first);
+		for (; nurbs; nurbs = nurbs->next, ++curve_idx) {
+			const int totpoint = (*num_vertices)[curve_idx];
+
+			if (nurbs->bp) {
+				BPoint *point = nurbs->bp;
+
+				for (int i = 0; i < totpoint; ++i, ++point, ++vertex_idx) {
+					const Imath::V3f &pos = (*positions)[vertex_idx];
+					copy_yup_zup(point->vec, pos.getValue());
+				}
+			}
+			else if (nurbs->bezt) {
+				BezTriple *bezier = nurbs->bezt;
+
+				for (int i = 0; i < totpoint; ++i, ++bezier, ++vertex_idx) {
+					const Imath::V3f &pos = (*positions)[vertex_idx];
+					copy_yup_zup(bezier->vec[1], pos.getValue());
+				}
+			}
+		}
+	}
+
+	return CDDM_from_curve(m_object);
+}