Assembly: Ball drag mode. (FreeCAD#26222)

Author: PaddleStroke

src/Mod/Assembly/Gui/ViewProviderAssembly.cpp

@@ -503,6 +503,28 @@ bool ViewProviderAssembly::tryMouseMove(const SbVec2s& cursorPos, Gui::View3DInv
                     Base::Placement jcsPlcRelativeToPart = plc.inverse() * jcsGlobalPlc;
                     plc = rotatedGlovalJcsPlc * jcsPlcRelativeToPart.inverse();
                 }
+                else if (dragMode == DragMode::Ball) {
+                    Base::Vector3d center = jcsGlobalPlc.getPosition();
+                    // Vectors from joint center to initial click and current drag position
+                    Base::Vector3d u = initialPosition - center;
+                    Base::Vector3d v = newPos - center;
+
+                    // Ensure vectors are valid to prevent singularities
+                    if (u.Length() > Precision::Confusion() && v.Length() > Precision::Confusion()) {
+                        // Calculate rotation that moves vector u to v
+                        Base::Rotation rot;
+                        rot.setValue(u, v);
+
+                        // Apply this rotation to the global joint placement (around the joint center)
+                        Base::Placement rotatedGlobalJcsPlc = jcsGlobalPlc;
+                        rotatedGlobalJcsPlc.setRotation(rot * jcsGlobalPlc.getRotation());
+
+                        // Calculate the initial offset of the part relative to the joint
+                        // and apply the new global joint placement to find the new part placement.
+                        Base::Placement jcsPlcRelativeToPart = plc.inverse() * jcsGlobalPlc;
+                        plc = rotatedGlobalJcsPlc * jcsPlcRelativeToPart.inverse();
+                    }
+                }
                 else if (dragMode == DragMode::TranslationOnAxis) {
                     Base::Vector3d pos = plc.getPosition() + (newPos - initialPosition);
                     plc.setPosition(pos);
@@ -942,7 +964,7 @@ ViewProviderAssembly::DragMode ViewProviderAssembly::findDragMode()
             return DragMode::TranslationOnAxisAndRotationOnePlane;
         }
         else if (jointType == JointType::Ball) {
-            // return DragMode::Ball;
+            return DragMode::Ball;
         }
         else if (jointType == JointType::Distance) {
             //  depends on the type of distance. For example plane-plane: