ENH: Add the ability to set linear projection constraint to restrict solution to a line

Source/Constraint/PbdConstraints/imstkLinearProjectionConstraint.cpp

@@ -41,6 +41,14 @@ LinearProjectionConstraint::setProjection(const size_t& nodeId, const Vec3d& p,
     m_projection = Mat3d::Identity() - p*p.transpose() - q*q.transpose();
 }
 
+void
+LinearProjectionConstraint::setProjectionToLine(const size_t& nodeId, const Vec3d& p)
+{
+    m_nodeId = nodeId;
+    auto v = p/p.norm();
+    m_projection = v*v.transpose();
+}
+
 void
 LinearProjectionConstraint::setProjectorToDirichlet(const unsigned int& nodeId, const Vec3d z)
 {

Source/Constraint/PbdConstraints/imstkLinearProjectionConstraint.h

@@ -50,6 +50,11 @@ public:
     ///
     void setProjection(const size_t& nodeId, const Vec3d& p, const Vec3d& q = Vec3d::Zero());
 
+    ///
+    /// \brief Form the projection
+    ///
+    void setProjectionToLine(const size_t& nodeId, const Vec3d& p);
+
     ///
     /// \brief Set the projector to simulate Dirichlet conditions
     ///