chore: virtual cam components iteration (#219)

* Removed the currently ignored 'fromEntity' / 'toEntity' suggestions in 'CameraTransition'
* Made 'MainCamera.VirtualCameraEntity' releasable with 'undefined' instead of '0' by making the field 'optional'
* Made 'VirtualCamera.DefaultTransition' as 'optional' and not mandatory so that a 'VirtualCamera.Create(entity)' is accepted and can still be used with a default instant/cut transition

proto/decentraland/sdk/components/common/camera_transition.proto

@@ -1,12 +1,11 @@
 syntax = "proto3";
 package decentraland.sdk.components.common;
 
+// Defines the transition used towards the camera that contains the CameraTransition.
+// This structure may be updated in the future to specify from/to entities and to have easing functions.
 message CameraTransition {
-  optional uint32 from_entity = 1;
-  optional uint32 to_entity = 2;
   oneof transition_mode {
-    float time = 3;
-    float speed = 4; // meters per second; e.g. speed 1 -> 1 meter per second
+    float time = 1;
+    float speed = 2; // meters per second; e.g. speed 1 -> 1 meter per second
   }
-  //   EasingFunction easing_function = 5; // enable in the future
 }

proto/decentraland/sdk/components/main_camera.proto

@@ -4,8 +4,8 @@ package decentraland.sdk.components;
 import "decentraland/sdk/components/common/id.proto";
 option (common.ecs_component_id) = 1075;
 
-// PBMainCamera.virtualCameraEntity defines which VirtualCamera entity is active at the moment. 0 means none.
+// PBMainCamera.virtualCameraEntity defines which VirtualCamera entity is active at the moment.
+// This component may hold 'repeated common.CameraTransition' transitionOverrides in the future
 message PBMainCamera {
-  uint32 virtual_camera_entity = 1; // currently active virtual camera (default: 0)
-//  repeated common.CameraTransition transitionOverrides = 2; // enable in the future
+  optional uint32 virtual_camera_entity = 1; // current active virtual camera
 }

proto/decentraland/sdk/components/virtual_camera.proto

@@ -6,10 +6,11 @@ import "decentraland/sdk/components/common/id.proto";
 option (common.ecs_component_id) = 1076;
 
 // PBVirtualCamera represents a camera to be used at some point in time during the scene execution
-// * The defaultTransition represents the transition TOWARDS this camera.
+// * The defaultTransition represents the transition TOWARDS this camera. If there is none, it's treated as
+// an 'instant' transition (like using speed/time = 0)
 // * The lookAtEntity defines to which entity the Camera has to look at constantly (independent from 
 // the holding entity transform).
 message PBVirtualCamera {
-  common.CameraTransition default_transition = 1;
+  optional common.CameraTransition default_transition = 1;
   optional uint32 look_at_entity = 2;
 }