From 7f99bdbef5c6e91daa8a536f3a69be094ae2daac Mon Sep 17 00:00:00 2001
From: William Tilton <william.tilton@caci.com>
Date: Thu, 22 Oct 2020 18:21:55 -0700
Subject: [PATCH] End

---
 Main.tscn       |  9 ++++-----
 Scripts/Main.gd | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/Main.tscn b/Main.tscn
index 6329402..22618d6 100644
--- a/Main.tscn
+++ b/Main.tscn
@@ -1,10 +1,8 @@
-[gd_scene load_steps=6 format=2]
+[gd_scene load_steps=5 format=2]
 
 [ext_resource path="res://Scripts/Main.gd" type="Script" id=1]
 [ext_resource path="res://Scripts/Camera.gd" type="Script" id=2]
 
-[sub_resource type="CubeMesh" id=6]
-
 [sub_resource type="SpatialMaterial" id=4]
 albedo_color = Color( 0.592157, 0.905882, 0.0862745, 1 )
 
@@ -14,12 +12,13 @@ material = SubResource( 4 )
 [node name="Main" type="Spatial"]
 transform = Transform( 1, 0, 0, 0, 0.99977, 0.021431, 0, -0.021431, 0.99977, 0, 0, 0 )
 script = ExtResource( 1 )
+show_wireframe = false
+show_axes = false
+show_face_normals = false
 
 [node name="Meshes" type="Node" parent="."]
 
 [node name="Cube" type="MeshInstance" parent="Meshes"]
-mesh = SubResource( 6 )
-material/0 = null
 
 [node name="Floor" type="MeshInstance" parent="Meshes"]
 transform = Transform( 6.88346, 0, 0, 0, 0.0447118, 0, 0, 0, 7.16078, 0, 0, 0 )
diff --git a/Scripts/Main.gd b/Scripts/Main.gd
index c7765d0..6f31276 100644
--- a/Scripts/Main.gd
+++ b/Scripts/Main.gd
@@ -253,3 +253,37 @@ func _on_StaticBody_mouse_exited():
 func _on_StaticBody_input_event(camera, event, click_position, click_normal, shape_idx):
 	if event.is_action_pressed("left_mouse"):
 		print("Pos ", click_position)
+		var face_index = get_hit_mesh_triangle_face_index(click_position)
+		if face_index > -1:
+			drawSelectedOutline(face_index)
+
+func get_hit_mesh_triangle_face_index(hitVector):
+	var cubeMeshInstance = get_node("Meshes/Cube")
+	var cubeMesh = cubeMeshInstance.get_mesh()
+	var vertices = cubeMesh.get_faces()
+	var arrayMesh = ArrayMesh.new()
+	var arrays = []
+	arrays.resize(ArrayMesh.ARRAY_MAX)
+	arrays[ArrayMesh.ARRAY_VERTEX] = vertices
+	arrayMesh.add_surface_from_arrays(Mesh.PRIMITIVE_TRIANGLES, arrays)
+	var meshDataTool = MeshDataTool.new()
+	meshDataTool.create_from_surface(arrayMesh, 0)
+	var camera_origin = camera.get_global_transform().origin
+	var purple_arrow = hitVector - camera_origin
+	var i = 0
+	while i < vertices.size():
+		var face_index = i / 3
+		var a = cubeMeshInstance.to_global(vertices[i])
+		var b = cubeMeshInstance.to_global(vertices[i + 1])
+		var c = cubeMeshInstance.to_global(vertices[i + 2])
+
+		var intersects_triangle = Geometry.ray_intersects_triangle(camera_origin, purple_arrow, a, b, c)
+
+		if intersects_triangle != null:
+			var angle = rad2deg(purple_arrow.angle_to(meshDataTool.get_face_normal(face_index)))
+			if angle > 90 and angle < 180:
+				return face_index
+
+		i += 3
+
+	return -1