Fix #107877: Alembic procedural crashes with point clouds

Somehow the implementation for the main function to load point clouds
data was missing although everything else to support point clouds was
there. Compilers were more than happy to convert the IPointsSchema to
another schema type for the compilation to succeed, and the crash
occurs because the points schema does not contain the same data as the
compiler's chosen schema (in this case an ICurvesSchema).

Another crash was found due to the radius array not being properly
initialized and left with a size of 0, when Cycles expects a full array.

intern/cycles/scene/alembic.cpp

@@ -611,6 +611,41 @@ void AlembicObject::load_data_in_cache(CachedData &cached_data,
   data_loaded = true;
 }
 
+void AlembicObject::load_data_in_cache(CachedData &cached_data,
+                                       AlembicProcedural *proc,
+                                       const IPointsSchema &schema,
+                                       Progress &progress)
+{
+  /* Only load data for the original Geometry. */
+  if (instance_of) {
+    return;
+  }
+
+  cached_data.clear();
+
+  PointsSchemaData data;
+  data.positions = schema.getPositionsProperty();
+  data.radiuses = schema.getWidthsParam();
+  data.velocities = schema.getVelocitiesProperty();
+  data.time_sampling = schema.getTimeSampling();
+  data.num_samples = schema.getNumSamples();
+  data.default_radius = proc->get_default_radius();
+  data.radius_scale = get_radius_scale();
+
+  read_geometry_data(proc, cached_data, data, progress);
+
+  if (progress.get_cancel()) {
+    return;
+  }
+
+  /* Use the schema as the base compound property to also be able to look for top level properties.
+   */
+  read_attributes(proc, cached_data, schema, {}, get_requested_attributes(), progress);
+
+  cached_data.invalidate_last_loaded_time(true);
+  data_loaded = true;
+}
+
 void AlembicObject::setup_transform_cache(CachedData &cached_data, float scale)
 {
   cached_data.transforms.clear();

intern/cycles/scene/alembic.h

@@ -398,6 +398,10 @@ class AlembicObject : public Node {
                           AlembicProcedural *proc,
                           const Alembic::AbcGeom::ICurvesSchema &schema,
                           Progress &progress);
+  void load_data_in_cache(CachedData &cached_data,
+                          AlembicProcedural *proc,
+                          const Alembic::AbcGeom::IPointsSchema &schema,
+                          Progress &progress);
 
   bool has_data_loaded() const;
 

intern/cycles/scene/alembic_read.cpp

@@ -663,8 +663,8 @@ static void read_points_data(CachedData &cached_data, const PointsSchemaData &da
 
     if (do_radius) {
       radius = (*radiuses)[offset + i];
-      a_radius.push_back_slow(radius);
     }
+    a_radius.push_back_slow(radius * data.radius_scale);
 
     a_shader.push_back_slow((int)0);
   }

intern/cycles/scene/alembic_read.h

@@ -110,7 +110,7 @@ void read_geometry_data(AlembicProcedural *proc,
                         const CurvesSchemaData &data,
                         Progress &progress);
 
-/* Data of a ICurvesSchema that we need to read. */
+/* Data of a IPointsSchema that we need to read. */
 struct PointsSchemaData {
   Alembic::AbcGeom::TimeSamplingPtr time_sampling;
   size_t num_samples;