add orbit camera support to FRED2 and qtFRED

Implement a spherical-coordinate orbit camera for both the MFC (FRED2)
and Qt (qtFRED) editors, providing intuitive 3D viewport navigation
similar to other 3D editing tools.

Controls:
- Middle mouse drag: orbit rotate around pivot point
- Shift + middle mouse drag: pan the pivot point
- Right mouse drag: orbit rotate (alternative to middle mouse)
- Shift + right mouse drag: pan (alternative to shift + middle mouse)
- Mouse wheel: zoom in/out
- Right click without drag: context menu (preserving existing feature)

Camera pivot selection:
- If an object is selected, orbit around that object
- Otherwise, intersect the camera forward ray with the current grid
  plane to find a natural pivot point
- Falls back to grid center if the camera is parallel to the grid

Grid-plane awareness:
- Orbit axes are derived from The_grid->gmatrix using vm_vec_rotate
  and vm_vec_unrotate, so the camera orbits correctly on all three
  grid planes (XZ, XY, YZ), not just the default XZ plane
- The look-at matrix uses the grid's up vector (uvec) rather than a
  hardcoded world-up direction

Robust zoom/pan scaling:
- Zoom uses an exponential formula (powf) so the distance multiplier
  is always positive regardless of physics_speed setting (1-500)
- Pan uses a clamped speed factor to avoid excessive movement at high
  physics_speed values

State management:
- Keyboard camera movement (process_controls) invalidates orbit state,
  so the next mouse drag re-initializes from the current view
- Orbit state is per-viewport in qtFRED (EditorViewport members) and
  global in FRED2 (matching existing conventions in each codebase)

Implementation:
- FRED2: orbit math in fredrender.cpp, mouse handlers in fredview.cpp
- qtFRED: orbit math in EditorViewport.cpp, mouse/wheel handlers in
  renderwidget.cpp; RenderWindow::event() updated to forward middle
  button and wheel events to RenderWidget

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Goober5000

fred2/fredrender.cpp

@@ -92,6 +92,13 @@ int Last_cursor_over = -1;
 int last_x = 0;
 int last_y = 0;
 int Lookat_mode = 0;
+
+// Orbit camera state
+vec3d Orbit_pivot = ZERO_VECTOR;
+float Orbit_distance = 200.0f;
+float Orbit_phi = 1.24f;
+float Orbit_theta = 2.25f;
+bool Orbit_active = false;
 int rendering_order[MAX_SHIPS];
 int render_count = 0;
 int Show_asteroid_field = 1;
@@ -1311,6 +1318,124 @@ void move_mouse(int btn, int mdx, int mdy) {
 	}
 }
 
+// ---------- Orbit camera functions ----------
+
+vec3d orbit_camera_get_pivot()
+{
+	vec3d pivot;
+
+	if (query_valid_object()) {
+		pivot = Objects[cur_object_index].pos;
+	} else if (!The_grid) {
+		pivot = ZERO_VECTOR;
+	} else {
+		// Intersect camera forward ray with the grid plane
+		vec3d *grid_normal = &The_grid->gmatrix.vec.uvec;
+		float denom = vm_vec_dot(grid_normal, &view_orient.vec.fvec);
+
+		if (fl_abs(denom) > 0.0001f) {
+			// t = -(dot(normal, view_pos) + planeD) / dot(normal, fvec)
+			float t = -(vm_vec_dot(grid_normal, &view_pos) + The_grid->planeD) / denom;
+			if (t > 0.0f) {
+				vm_vec_scale_add(&pivot, &view_pos, &view_orient.vec.fvec, t);
+			} else {
+				pivot = The_grid->center;
+			}
+		} else {
+			// Camera is parallel to grid plane; fall back to grid center
+			pivot = The_grid->center;
+		}
+	}
+	return pivot;
+}
+
+void orbit_camera_init_from_current_view(const vec3d *pivot)
+{
+	vec3d offset;
+	vm_vec_sub(&offset, &view_pos, pivot);
+
+	Orbit_distance = vm_vec_mag(&offset);
+	if (Orbit_distance < 1.0f)
+		Orbit_distance = 100.0f;
+
+	// Transform offset into grid-local frame for angle decomposition
+	// In local frame, Y is always "up" (the grid plane normal)
+	const matrix &grid_mat = The_grid ? The_grid->gmatrix : vmd_identity_matrix;
+	vec3d local_offset;
+	vm_vec_rotate(&local_offset, &offset, &grid_mat);
+
+	Orbit_phi = acosf(std::clamp(local_offset.xyz.y / Orbit_distance, -1.0f, 1.0f));
+	Orbit_theta = atan2f(local_offset.xyz.z, local_offset.xyz.x);
+	Orbit_pivot = *pivot;
+	Orbit_active = true;
+}
+
+void orbit_camera_apply()
+{
+	float sp = sinf(Orbit_phi);
+
+	// Build offset in grid-local coordinates (Y = up/normal)
+	vec3d local_pos;
+	local_pos.xyz.x = sp * cosf(Orbit_theta);
+	local_pos.xyz.y = cosf(Orbit_phi);
+	local_pos.xyz.z = sp * sinf(Orbit_theta);
+
+	// Transform back to world space
+	const matrix &grid_mat = The_grid ? The_grid->gmatrix : vmd_identity_matrix;
+	vec3d world_offset;
+	vm_vec_unrotate(&world_offset, &local_pos, &grid_mat);
+
+	vm_vec_scale(&world_offset, Orbit_distance);
+	vm_vec_add(&view_pos, &Orbit_pivot, &world_offset);
+
+	// Point camera at pivot, using grid's up vector
+	vec3d look_dir;
+	vm_vec_sub(&look_dir, &Orbit_pivot, &view_pos);
+	if (vm_vec_mag(&look_dir) > 0.001f) {
+		vec3d grid_up = grid_mat.vec.uvec;
+		vm_vector_2_matrix(&view_orient, &look_dir, &grid_up, nullptr);
+	}
+
+	Update_window = 1;
+}
+
+void orbit_camera_rotate(int dx, int dy)
+{
+	float rot_scale = physics_rot / 300.0f;
+	Orbit_theta += dx / 100.0f * rot_scale;
+	Orbit_phi += dy / 100.0f * rot_scale;
+
+	CLAMP(Orbit_phi, 0.01f, PI - 0.01f);
+
+	orbit_camera_apply();
+}
+
+void orbit_camera_pan(int dx, int dy)
+{
+	float speed_factor = 1.0f + (physics_speed - 1) / 499.0f * 9.0f;
+	float pan_scale = Orbit_distance * 0.002f * speed_factor;
+
+	vec3d pan_delta;
+	vm_vec_copy_scale(&pan_delta, &view_orient.vec.rvec, -(float)dx * pan_scale);
+	vm_vec_scale_add2(&pan_delta, &view_orient.vec.uvec, (float)dy * pan_scale);
+
+	vm_vec_add2(&Orbit_pivot, &pan_delta);
+
+	orbit_camera_apply();
+}
+
+void orbit_camera_zoom(float delta)
+{
+	float zoom_speed = 1.0f + (physics_speed - 1) / 499.0f * 4.0f;
+	Orbit_distance *= powf(2.0f, delta * zoom_speed);
+
+	CLAMP(Orbit_distance, 1.0f, 10000000.0f);
+
+	orbit_camera_apply();
+}
+
+// ---------- End orbit camera functions ----------
+
 int object_check_collision(object *objp, vec3d *p0, vec3d *p1, vec3d *hitpos) {
 	mc_info mc;
 
@@ -1425,6 +1550,9 @@ void process_controls(vec3d *pos, matrix *orient, float frametime, int key, int
 		if (rotangs.h && Universal_heading)
 			vm_transpose(orient);
 	}
+
+	// Invalidate orbit camera state so it re-initializes on next mouse drag
+	Orbit_active = false;
 }
 
 void process_movement_keys(int key, vec3d *mvec, angles *angs) {

fred2/fredrender.h

@@ -35,6 +35,13 @@ extern int Flying_controls_mode;    //!< Bool. Unknown.
 extern int Group_rotate;            //!< Bool. If nonzero, each object rotates around the leader. If zero. rotate
 extern int Show_horizon;            //!< Bool. If nonzero, draw a line representing the horizon (XZ plane)
 extern int Lookat_mode;             //!< Bool. Unknown.
+
+// Orbit camera state
+extern vec3d Orbit_pivot;
+extern float Orbit_distance;
+extern float Orbit_phi;
+extern float Orbit_theta;
+extern bool Orbit_active;
 extern int True_rw;                 //!< Unsigned. The width of the render area
 extern int True_rh;                 //!< Unsigned. The height of the render area
 extern int Fixed_briefing_size;     //!< Bool. If nonzero then expand the briefing preview as much as we can, maintaining the aspect ratio.
@@ -93,3 +100,11 @@ void verticalize_controlled();
  * @return -1 if no object found
  */
 int select_object(int cx, int cy);
+
+// Orbit camera functions
+vec3d orbit_camera_get_pivot();
+void orbit_camera_init_from_current_view(const vec3d *pivot);
+void orbit_camera_apply();
+void orbit_camera_rotate(int dx, int dy);
+void orbit_camera_pan(int dx, int dy);
+void orbit_camera_zoom(float delta);

fred2/fredview.cpp

@@ -158,6 +158,11 @@ BEGIN_MESSAGE_MAP(CFREDView, CView)
 	ON_WM_SIZE()
 	ON_WM_MOUSEMOVE()
 	ON_WM_LBUTTONUP()
+	ON_WM_MBUTTONDOWN()
+	ON_WM_MBUTTONUP()
+	ON_WM_RBUTTONDOWN()
+	ON_WM_RBUTTONUP()
+	ON_WM_MOUSEWHEEL()
 	ON_COMMAND(ID_MISCSTUFF_SHOWSHIPSASICONS, OnMiscstuffShowshipsasicons)
 	ON_WM_CONTEXTMENU()
 	ON_COMMAND(ID_EDIT_POPUP_SHOW_SHIP_ICONS, OnEditPopupShowShipIcons)
@@ -1038,7 +1043,7 @@ void CFREDView::OnLButtonDown(UINT nFlags, CPoint point)
 	CView::OnLButtonDown(nFlags, point);
 }
 
-void CFREDView::OnMouseMove(UINT nFlags, CPoint point) 
+void CFREDView::OnMouseMove(UINT nFlags, CPoint point)
 {
 	// RT point
 
@@ -1048,6 +1053,26 @@ void CFREDView::OnMouseMove(UINT nFlags, CPoint point)
 	last_mouse_y = marking_box.y2 = point.y;
 	Cursor_over = select_object(point.x, point.y);
 
+	// Orbit camera: middle button drag
+	if (m_orbit_dragging && (nFlags & MK_MBUTTON)) {
+		handle_orbit_drag(point, nFlags);
+		CView::OnMouseMove(nFlags, point);
+		return;
+	}
+
+	// Orbit camera: right button drag
+	if (m_rbutton_down && (nFlags & MK_RBUTTON) && viewpoint == 0 && Control_mode == 0) {
+		if (!m_rbutton_moved) {
+			if (abs(point.x - m_rbutton_down_point.x) > 2 || abs(point.y - m_rbutton_down_point.y) > 2)
+				m_rbutton_moved = true;
+		}
+		if (m_rbutton_moved) {
+			handle_orbit_drag(point, nFlags);
+			CView::OnMouseMove(nFlags, point);
+			return;
+		}
+	}
+
 	if (!(nFlags & MK_LBUTTON))
 		button_down = 0;
 
@@ -1056,7 +1081,7 @@ void CFREDView::OnMouseMove(UINT nFlags, CPoint point)
 	if (button_down && GetCapture() != this)
 		cancel_drag();
 
-	if (!button_down && GetCapture() == this)
+	if (!button_down && !m_orbit_dragging && !m_rbutton_down && GetCapture() == this)
 		ReleaseCapture();
 
 	if (button_down) {
@@ -1089,7 +1114,7 @@ void CFREDView::OnLButtonUp(UINT nFlags, CPoint point)
 	if (button_down && GetCapture() != this)
 		cancel_drag();
 
-	if (GetCapture() == this)
+	if (!m_orbit_dragging && !m_rbutton_down && GetCapture() == this)
 		ReleaseCapture();
 
 	if (button_down) {
@@ -1174,6 +1199,89 @@ void CFREDView::OnLButtonUp(UINT nFlags, CPoint point)
 	CView::OnLButtonUp(nFlags, point);
 }
 
+// ---------- Orbit camera mouse handlers ----------
+
+void CFREDView::handle_orbit_drag(CPoint point, UINT nFlags)
+{
+	int dx = point.x - m_orbit_last_mouse.x;
+	int dy = point.y - m_orbit_last_mouse.y;
+	m_orbit_last_mouse = point;
+
+	if (nFlags & MK_SHIFT)
+		orbit_camera_pan(dx, dy);
+	else
+		orbit_camera_rotate(dx, dy);
+}
+
+void CFREDView::OnMButtonDown(UINT nFlags, CPoint point)
+{
+	if (viewpoint != 0 || Control_mode != 0)
+		return;
+
+	vec3d pivot = orbit_camera_get_pivot();
+	orbit_camera_init_from_current_view(&pivot);
+
+	m_orbit_dragging = true;
+	m_orbit_last_mouse = point;
+	SetCapture();
+}
+
+void CFREDView::OnMButtonUp(UINT nFlags, CPoint point)
+{
+	if (m_orbit_dragging) {
+		m_orbit_dragging = false;
+		if (GetCapture() == this && !m_rbutton_down)
+			ReleaseCapture();
+	}
+}
+
+void CFREDView::OnRButtonDown(UINT nFlags, CPoint point)
+{
+	m_rbutton_down = true;
+	m_rbutton_moved = false;
+	m_rbutton_down_point = point;
+	m_orbit_last_mouse = point;
+
+	if (viewpoint == 0 && Control_mode == 0) {
+		vec3d pivot = orbit_camera_get_pivot();
+		orbit_camera_init_from_current_view(&pivot);
+		SetCapture();
+	}
+}
+
+void CFREDView::OnRButtonUp(UINT nFlags, CPoint point)
+{
+	bool was_dragging = m_rbutton_moved;
+	m_rbutton_down = false;
+	m_rbutton_moved = false;
+
+	if (GetCapture() == this && !m_orbit_dragging)
+		ReleaseCapture();
+
+	if (!was_dragging) {
+		// No drag occurred — show context menu as normal
+		CPoint screen_point = point;
+		ClientToScreen(&screen_point);
+		OnContextMenu(this, screen_point);
+	}
+}
+
+BOOL CFREDView::OnMouseWheel(UINT nFlags, short zDelta, CPoint pt)
+{
+	if (viewpoint != 0 || Control_mode != 0)
+		return CView::OnMouseWheel(nFlags, zDelta, pt);
+
+	if (!Orbit_active) {
+		vec3d pivot = orbit_camera_get_pivot();
+		orbit_camera_init_from_current_view(&pivot);
+	}
+
+	orbit_camera_zoom(zDelta / -200.0f);
+	return TRUE;
+}
+
+// ---------- End orbit camera mouse handlers ----------
+
 //	This function never gets called because nothing causes
 //	the WM_GOODBYE event to occur.
 // False! When you close the Ship Dialog, this function is called! --MK, 8/30/96

fred2/fredview.h

@@ -36,6 +36,14 @@ class CFREDView : public CView
 	CGrid*		m_pGDlg;
 	int global_error_check_player_wings(int multi);
 
+	// Orbit camera drag state
+	bool m_orbit_dragging = false;
+	bool m_rbutton_down = false;
+	bool m_rbutton_moved = false;
+	CPoint m_orbit_last_mouse;
+	CPoint m_rbutton_down_point;
+	void handle_orbit_drag(CPoint point, UINT nFlags);
+
 protected: // create from serialization only
 	CFREDView();
 	DECLARE_DYNCREATE(CFREDView)
@@ -331,6 +339,11 @@ class CFREDView : public CView
 	afx_msg void OnUpdateViewLighting(CCmdUI* pCmdUI);
 	afx_msg void OnViewFullDetail();
 	afx_msg void OnUpdateViewFullDetail(CCmdUI *pCmdUI);
+	afx_msg void OnMButtonDown(UINT nFlags, CPoint point);
+	afx_msg void OnMButtonUp(UINT nFlags, CPoint point);
+	afx_msg void OnRButtonDown(UINT nFlags, CPoint point);
+	afx_msg void OnRButtonUp(UINT nFlags, CPoint point);
+	afx_msg BOOL OnMouseWheel(UINT nFlags, short zDelta, CPoint pt);
 	//}}AFX_MSG
 	afx_msg void OnGroup(UINT nID);
 	afx_msg void OnSetGroup(UINT nID);