From 0dbe7b9cc17e7ba409504ba24374b7678661dee6 Mon Sep 17 00:00:00 2001
From: Dion Moult <dion@thinkmoult.com>
Date: Fri, 7 Aug 2020 20:00:45 +1000
Subject: [PATCH] Add perimeter quantity calculation

---
 src/ifcblenderexport/blenderbim/bim/qto.py | 33 ++++++++++++++++++++++
 src/ifcblenderexport/blenderbim/bim/ui.py  |  3 +-
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/src/ifcblenderexport/blenderbim/bim/qto.py b/src/ifcblenderexport/blenderbim/bim/qto.py
index 77f27d7a2d..b41eb325ca 100644
--- a/src/ifcblenderexport/blenderbim/bim/qto.py
+++ b/src/ifcblenderexport/blenderbim/bim/qto.py
@@ -17,6 +17,8 @@ class QtoCalculator():
             return self.get_width(obj)
         elif 'height' in prop_name or 'depth' in prop_name:
             return self.get_height(obj)
+        elif 'perimeter' in prop_name:
+            return self.get_perimeter(obj)
         elif 'area' in prop_name \
                 and ('footprint' in prop_name or 'section' in prop_name):
             return self.get_footprint_area(obj)
@@ -59,6 +61,37 @@ class QtoCalculator():
     def get_height(self, o):
         return (Vector(o.bound_box[1]) - Vector(o.bound_box[0])).length
 
+    def get_perimeter(self, o):
+        lowest_polygons = []
+        lowest_z = None
+        for polygon in o.data.polygons:
+            z = round(polygon.center[2], 3)
+            if lowest_z is None:
+                lowest_z = z
+            if z > lowest_z:
+                continue
+            elif z == lowest_z:
+                lowest_polygons.append(polygon)
+            elif z < lowest_z:
+                lowest_polygons = [polygon]
+                lowest_z = z
+        parsed_edges = []
+        shared_edges = []
+        perimeter = 0
+        for polygon in lowest_polygons:
+            for edge_key in polygon.edge_keys:
+                if edge_key in parsed_edges:
+                    shared_edges.append(edge_key)
+                else:
+                    parsed_edges.append(edge_key)
+                    perimeter += self.get_edge_key_distance(o, edge_key)
+        for edge_key in shared_edges:
+            perimeter -= self.get_edge_key_distance(o, edge_key)
+        return perimeter
+
+    def get_edge_key_distance(self, obj, edge_key):
+        return (obj.data.vertices[edge_key[1]].co - obj.data.vertices[edge_key[0]].co).length
+
     def get_edge_distance(self, obj, edge):
         return (obj.data.vertices[edge.vertices[1]].co - obj.data.vertices[edge.vertices[0]].co).length
 
diff --git a/src/ifcblenderexport/blenderbim/bim/ui.py b/src/ifcblenderexport/blenderbim/bim/ui.py
index bf610a1308..a149f0e0fb 100644
--- a/src/ifcblenderexport/blenderbim/bim/ui.py
+++ b/src/ifcblenderexport/blenderbim/bim/ui.py
@@ -106,7 +106,8 @@ class BIM_PT_object(Panel):
                 if 'length' in prop.name.lower() \
                         or 'width' in prop.name.lower() \
                         or 'height' in prop.name.lower() \
-                        or 'depth' in prop.name.lower():
+                        or 'depth' in prop.name.lower() \
+                        or 'perimeter' in prop.name.lower():
                     op = row.operator('bim.guess_quantity', icon='IPO_EASE_IN_OUT', text='')
                     op.qto_index = index
                     op.prop_index = index2