Cycles: add Alembic procedural to Cycles standalone xml

Example:

<alembic filepath="/tmp/cube.abc" scale="1.45">
  <object path="/Cube/Cube" />
</alembic>

Differential Revision: https://developer.blender.org/D14391

intern/cycles/app/CMakeLists.txt

@@ -22,6 +22,16 @@ set(LIBRARIES
   cycles_util
 )
 
+if(WITH_ALEMBIC)
+  add_definitions(-DWITH_ALEMBIC)
+  list(APPEND INC_SYS
+    ${ALEMBIC_INCLUDE_DIRS}
+  )
+  list(APPEND LIB
+    ${ALEMBIC_LIBRARIES}
+  )
+endif()
+
 if(WITH_CYCLES_OSL)
   list(APPEND LIBRARIES cycles_kernel_osl)
 endif()

intern/cycles/app/cycles_xml.cpp

@@ -9,6 +9,7 @@
 
 #include "graph/node_xml.h"
 
+#include "scene/alembic.h"
 #include "scene/background.h"
 #include "scene/camera.h"
 #include "scene/film.h"
@@ -192,6 +193,31 @@ static void xml_read_camera(XMLReadState &state, xml_node node)
   cam->update(state.scene);
 }
 
+/* Alembic */
+
+#ifdef WITH_ALEMBIC
+static void xml_read_alembic(XMLReadState &state, xml_node graph_node)
+{
+  AlembicProcedural *proc = state.scene->create_node<AlembicProcedural>();
+  xml_read_node(state, proc, graph_node);
+
+  for (xml_node node = graph_node.first_child(); node; node = node.next_sibling()) {
+    if (string_iequals(node.name(), "object")) {
+      string path;
+      if (xml_read_string(&path, node, "path")) {
+        ustring object_path(path, 0);
+        AlembicObject *object = static_cast<AlembicObject *>(
+            proc->get_or_create_object(object_path));
+
+        array<Node *> used_shaders = object->get_used_shaders();
+        used_shaders.push_back_slow(state.shader);
+        object->set_used_shaders(used_shaders);
+      }
+    }
+  }
+}
+#endif
+
 /* Shader */
 
 static void xml_read_shader_graph(XMLReadState &state, Shader *shader, xml_node graph_node)
@@ -647,6 +673,11 @@ static void xml_read_scene(XMLReadState &state, xml_node scene_node)
       if (xml_read_string(&src, node, "src"))
         xml_read_include(state, src);
     }
+#ifdef WITH_ALEMBIC
+    else if (string_iequals(node.name(), "alembic")) {
+      xml_read_alembic(state, node);
+    }
+#endif
     else
       fprintf(stderr, "Unknown node \"%s\".\n", node.name());
   }