From 6c36577e8e48e27a372f9a53cd2ba2a07e3a49a3 Mon Sep 17 00:00:00 2001
From: Enrico Turri <enricoturri@seznam.cz>
Date: Mon, 9 Mar 2020 15:23:29 +0100
Subject: [PATCH] #3782 - World Z axis always vertical for non-free camera

---
 src/slic3r/GUI/Camera.cpp     | 3 ++-
 src/slic3r/GUI/Camera.hpp     | 3 ++-
 src/slic3r/GUI/GLCanvas3D.cpp | 1 -
 src/slic3r/GUI/Plater.cpp     | 8 ++++++++
 4 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/src/slic3r/GUI/Camera.cpp b/src/slic3r/GUI/Camera.cpp
index 0a0b02c6f..74c21d3e8 100644
--- a/src/slic3r/GUI/Camera.cpp
+++ b/src/slic3r/GUI/Camera.cpp
@@ -260,7 +260,7 @@ void Camera::debug_render() const
     imgui.begin(std::string("Camera statistics"), ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoCollapse);
 
     std::string type = get_type_as_string();
-    if (wxGetApp().plater()->get_mouse3d_controller().is_running() || (wxGetApp().app_config->get("use_free_camera") == "1"))
+    if (wxGetApp().plater()->get_mouse3d_controller().connected() || (wxGetApp().app_config->get("use_free_camera") == "1"))
         type += "/free";
     else
         type += "/constrained";
@@ -537,6 +537,7 @@ void Camera::look_at(const Vec3d& position, const Vec3d& target, const Vec3d& up
     Vec3d unit_y = unit_z.cross(unit_x).normalized();
 
     m_target = target;
+    m_distance = (position - target).norm();
     Vec3d new_position = m_target + m_distance * unit_z;
 
     m_view_matrix(0, 0) = unit_x(0);
diff --git a/src/slic3r/GUI/Camera.hpp b/src/slic3r/GUI/Camera.hpp
index f592dbcd2..4b9144519 100644
--- a/src/slic3r/GUI/Camera.hpp
+++ b/src/slic3r/GUI/Camera.hpp
@@ -122,6 +122,8 @@ public:
     // returns true if the camera z axis (forward) is pointing in the negative direction of the world z axis
     bool is_looking_downward() const { return get_dir_forward().dot(Vec3d::UnitZ()) < 0.0; }
 
+    void look_at(const Vec3d& position, const Vec3d& target, const Vec3d& up);
+
     double max_zoom() const { return 100.0; }
     double min_zoom() const;
 
@@ -137,7 +139,6 @@ private:
 #endif // ENABLE_THUMBNAIL_GENERATOR
     void set_distance(double distance) const;
 
-    void look_at(const Vec3d& position, const Vec3d& target, const Vec3d& up);
     void set_default_orientation();
     Vec3d validate_target(const Vec3d& target) const;
     void update_zenit();
diff --git a/src/slic3r/GUI/GLCanvas3D.cpp b/src/slic3r/GUI/GLCanvas3D.cpp
index 540f82b4c..fc8a800d1 100644
--- a/src/slic3r/GUI/GLCanvas3D.cpp
+++ b/src/slic3r/GUI/GLCanvas3D.cpp
@@ -3932,7 +3932,6 @@ void GLCanvas3D::handle_layers_data_focus_event(const t_layer_height_range range
 
 void GLCanvas3D::update_ui_from_settings()
 {
-    m_camera.set_type(wxGetApp().app_config->get("use_perspective_camera"));
     m_dirty = true;
 
 #if ENABLE_RETINA_GL
diff --git a/src/slic3r/GUI/Plater.cpp b/src/slic3r/GUI/Plater.cpp
index 48eb86743..c20764067 100644
--- a/src/slic3r/GUI/Plater.cpp
+++ b/src/slic3r/GUI/Plater.cpp
@@ -2245,6 +2245,14 @@ void Plater::priv::update_ui_from_settings()
     //     $self->{buttons_sizer}->Layout;
     // }
 
+    camera.set_type(wxGetApp().app_config->get("use_perspective_camera"));
+    if (wxGetApp().app_config->get("use_free_camera") != "1")
+    {
+        // forces camera right vector to be parallel to XY plane
+        if (std::abs(camera.get_dir_right()(2)) > EPSILON)
+            camera.look_at(camera.get_position(), camera.get_target(), Vec3d::UnitZ());
+    }
+
     view3D->get_canvas3d()->update_ui_from_settings();
     preview->get_canvas3d()->update_ui_from_settings();
 }