Add camera rigs: add 2D camera rig

This rig is mostly useful for 2D shots, when the camera is static and
the action happens in front of it (like a theatre stage).

In a 2D production (and some shots in 3D as well), you sometimes need
to rotate the camera while zooming, effectively "cropping" the field,
just as you would using a rostrum camera. This is tedious and
error-prone if animating built-in basic transforms, so this rig
implements a more intuitive way to do that, by just animating the two
lower corners of the camera's field.

Also improved other stuff in the add-on:
- add the GPL license block to create_widgets.py;
- rename "arm[ature]" to "rig" in some functions, for consistency and
  to avoid confusion with the crane's arm;
- changes to the UI panel:
  - remove the boxes,
  - put focal length at the top of the panel,
  - group related properties using aligned columns,
  - change the Make Camera Active operator's poll method, so that it
    is always visible in the UI, but greyed out when the camera is
    already active.

1 files changed, 21 insertions, 14 deletions

diff --git a/add_camera_rigs/operators.py b/add_camera_rigs/operators.py
index 7468007e..058ed146 100644
--- a/add_camera_rigs/operators.py
+++ b/add_camera_rigs/operators.py
@@ -20,7 +20,7 @@ import bpy
 from bpy.types import Operator
 
 
-def get_arm_and_cam(obj):
+def get_rig_and_cam(obj):
     if obj.type == 'ARMATURE':
         cam = None
         for child in obj.children:
@@ -32,7 +32,8 @@ def get_arm_and_cam(obj):
     elif (obj.type == 'CAMERA'
           and obj.parent is not None
           and "rig_id" in obj.parent
-          and obj.parent["rig_id"].lower() in {"dolly_rig", "crane_rig"}):
+          and obj.parent["rig_id"].lower() in {"dolly_rig",
+                                               "crane_rig", "2d_rig"}):
         return obj.parent, obj
     return None, None
 
@@ -41,25 +42,31 @@ class CameraRigMixin():
     @classmethod
     def poll(cls, context):
         if context.active_object is not None:
-            return get_arm_and_cam(context.active_object) != (None, None)
+            return get_rig_and_cam(context.active_object) != (None, None)
 
         return False
 
 
-class ADD_CAMERA_RIGS_OT_set_scene_camera(Operator, CameraRigMixin):
+class ADD_CAMERA_RIGS_OT_set_scene_camera(Operator):
     bl_idname = "add_camera_rigs.set_scene_camera"
     bl_label = "Make Camera Active"
     bl_description = "Makes the camera parented to this rig the active scene camera"
 
+    @classmethod
+    def poll(cls, context):
+        if context.active_object is not None:
+            rig, cam = get_rig_and_cam(context.active_object)
+            if cam is not None:
+                return cam is not context.scene.camera
+
+        return False
+
     def execute(self, context):
-        arm, cam = get_arm_and_cam(context.active_object)
+        rig, cam = get_rig_and_cam(context.active_object)
         scene_cam = context.scene.camera
 
-        if cam is not None and cam is not scene_cam:
-            context.scene.camera = cam
-            return {'FINISHED'}
-
-        return {'CANCELLED'}
+        context.scene.camera = cam
+        return {'FINISHED'}
 
 
 class ADD_CAMERA_RIGS_OT_add_marker_bind(Operator, CameraRigMixin):
@@ -68,7 +75,7 @@ class ADD_CAMERA_RIGS_OT_add_marker_bind(Operator, CameraRigMixin):
     bl_description = "Add marker to current frame then bind rig camera to it (for camera switching)"
 
     def execute(self, context):
-        arm, cam = get_arm_and_cam(context.active_object)
+        rig, cam = get_rig_and_cam(context.active_object)
 
         marker = context.scene.timeline_markers.new(
             "cam_" + str(context.scene.frame_current),
@@ -85,15 +92,15 @@ class ADD_CAMERA_RIGS_OT_add_dof_object(Operator, CameraRigMixin):
     bl_description = "Create Empty and add as DOF Object"
 
     def execute(self, context):
-        arm, cam = get_arm_and_cam(context.active_object)
-        bone = arm.data.bones['Aim_shape_rotation-MCH']
+        rig, cam = get_rig_and_cam(context.active_object)
+        bone = rig.data.bones['Aim_shape_rotation-MCH']
 
         # Add Empty
         empty_obj = bpy.data.objects.new("EmptyDOF", None)
         context.scene.collection.objects.link(empty_obj)
 
         # Parent to Aim Child bone
-        empty_obj.parent = arm
+        empty_obj.parent = rig
         empty_obj.parent_type = "BONE"
         empty_obj.parent_bone = "Aim_shape_rotation-MCH"