mockingbirdnest · Jan 1, 2022 · Jan 1, 2022 · Jan 1, 2022
Showing with 40 additions and 10 deletions.

+12 −0 ksp_plugin/frames.hpp

+2 −1 ksp_plugin/interface_renderer.cpp

+9 −0 ksp_plugin/plugin.cpp

+4 −0 ksp_plugin/plugin.hpp

+8 −7 ksp_plugin/renderer.cpp

+4 −2 ksp_plugin/renderer.hpp

+1 −0 serialization/geometry.proto
diff --git a/ksp_plugin/frames.hpp b/ksp_plugin/frames.hpp
@@ -99,6 +99,17 @@ using CameraReference = Frame<serialization::Frame::PluginTag,
                               Handedness::Left,
                               serialization::Frame::CAMERA_REFERENCE>;
 
+// |CameraReference|, rotated about its y axis by the angle of the planetarium
+// rotation.  KSP compensates for the planetarium rotation so that the
+// orientation of the camera remains inertially fixed regardless of whether
+// World is rotating; we must undo this compensation in order for the camera to
+// be fixed in |CameraReference|.
+using CameraCompensatedReference =
+    Frame<serialization::Frame::PluginTag,
+          Arbitrary,
+          Handedness::Left,
+          serialization::Frame::CAMERA_COMPENSATED_REFERENCE>;
+
 // A nonrotating referencence frame comoving with the sun with the same axes as
 // |AliceWorld|. Since it is nonrotating (though not inertial), differences
 // between velocities are consistent with those in an inertial reference frame.
@@ -162,6 +173,7 @@ using internal_frames::ApparentWorld;
 using internal_frames::Barycentric;
 using internal_frames::BodyWorld;
 using internal_frames::Camera;
+using internal_frames::CameraCompensatedReference;
 using internal_frames::CameraReference;
 using internal_frames::CelestialSphere;
 using internal_frames::EccentricPart;

diff --git a/ksp_plugin/interface_renderer.cpp b/ksp_plugin/interface_renderer.cpp
@@ -145,7 +145,8 @@ WXYZ __cdecl principia__CameraReferenceRotation(Plugin* const plugin) {
   return m.Return(
       ToWXYZ(GetRenderer(plugin)
                  .CameraReferenceRotation(plugin->CurrentTime(),
-                                          plugin->PlanetariumRotation())
+                                          plugin->PlanetariumRotation(),
+                                          plugin->CameraCompensation())
                  .quaternion()));
 }
 

diff --git a/ksp_plugin/plugin.cpp b/ksp_plugin/plugin.cpp
@@ -1294,6 +1294,11 @@ Rotation<Barycentric, AliceSun> const& Plugin::PlanetariumRotation() const {
   return *cached_planetarium_rotation_;
 }
 
+Rotation<CameraCompensatedReference, CameraReference> const&
+Plugin::CameraCompensation() const {
+  return *camera_compensation_;
+}
+
 Renderer& Plugin::renderer() {
   return *renderer_;
 }
@@ -1574,6 +1579,10 @@ void Plugin::UpdatePlanetariumRotation() {
           Bivector<double, PlanetariumFrame>({0, 0, 1}),
           DefinesFrame<AliceSun>{}) *
       to_planetarium;
+  camera_compensation_ = Rotation<CameraCompensatedReference, CameraReference>(
+      -planetarium_rotation_,
+      Bivector<double, CameraReference>({0, 1, 0}),
+      DefinesFrame<CameraCompensatedReference>{});
 }
 
 Velocity<World> Plugin::VesselVelocity(

diff --git a/ksp_plugin/plugin.hpp b/ksp_plugin/plugin.hpp
@@ -443,6 +443,8 @@ class Plugin {
   // this change of basis is all that's required to convert relative velocities
   // or displacements between simultaneous events.
   virtual Rotation<Barycentric, AliceSun> const& PlanetariumRotation() const;
+  virtual Rotation<CameraCompensatedReference, CameraReference> const&
+  CameraCompensation() const;
 
   virtual Renderer& renderer();
   virtual Renderer const& renderer() const;
@@ -534,6 +536,8 @@ class Plugin {
 
   Angle planetarium_rotation_;
   std::optional<Rotation<Barycentric, AliceSun>> cached_planetarium_rotation_;
+  std::optional<Rotation<CameraCompensatedReference, CameraReference>>
+      camera_compensation_;
   // The game epoch in real time.
   Instant game_epoch_;
   // The current in-game universal time.

diff --git a/ksp_plugin/renderer.cpp b/ksp_plugin/renderer.cpp
@@ -278,18 +278,19 @@ RigidTransformation<World, Navigation> Renderer::WorldToPlotting(
          WorldToBarycentric(time, sun_world_position, planetarium_rotation);
 }
 
-Rotation<CameraReference, CelestialSphere> Renderer::CameraReferenceRotation(
+Rotation<CameraCompensatedReference, World> Renderer::CameraReferenceRotation(
     Instant const& time,
-    Rotation<Barycentric, AliceSun> const& planetarium_rotation) const {
+    Rotation<Barycentric, AliceSun> const& planetarium_rotation,
+    Rotation<CameraCompensatedReference, CameraReference> const&
+        camera_compensation) const {
   Permutation<Barycentric, CelestialSphere> const celestial_mirror(
       OddPermutation::XZY);
   Permutation<CameraReference, Navigation> const camera_mirror(
       OddPermutation::XZY);
-  auto const result =
-      celestial_mirror.Forget<OrthogonalMap>() *
-      GetPlottingFrame()->FromThisFrameAtTime(time).orthogonal_map() *
-      camera_mirror.Forget<OrthogonalMap>();
-  return result.AsRotation();
+  return (BarycentricToWorld(planetarium_rotation) *
+          GetPlottingFrame()->FromThisFrameAtTime(time).orthogonal_map() *
+          camera_mirror.Forget<OrthogonalMap>()).AsRotation() *
+         camera_compensation;
 }
 
 void Renderer::WriteToMessage(

diff --git a/ksp_plugin/renderer.hpp b/ksp_plugin/renderer.hpp
@@ -159,9 +159,11 @@ class Renderer {
       Position<World> const& sun_world_position,
       Rotation<Barycentric, AliceSun> const& planetarium_rotation) const;
 
-  virtual Rotation<CameraReference, CelestialSphere> CameraReferenceRotation(
+  virtual Rotation<CameraCompensatedReference, World> CameraReferenceRotation(
       Instant const& time,
-      Rotation<Barycentric, AliceSun> const& planetarium_rotation) const;
+      Rotation<Barycentric, AliceSun> const& planetarium_rotation,
+      Rotation<CameraCompensatedReference, CameraReference> const&
+          camera_compensation) const;
 
   virtual void WriteToMessage(not_null<serialization::Renderer*> message) const;
 

diff --git a/serialization/geometry.proto b/serialization/geometry.proto
@@ -159,6 +159,7 @@ message Frame {
     BODY_WORLD = 9;
     // BUBBLE = 13;
     CAMERA = 14;
+    CAMERA_COMPENSATED_REFERENCE = 21;
     CAMERA_REFERENCE = 17;
     CELESTIAL_SPHERE = 8;
     ECCENTRIC_PART = 20;