feat: add TRS serialization and display property support to MultiSelectionProp

src/Vtk/uLibVtkInterface.cxx

@@ -569,6 +569,18 @@ void Prop3D::SetOpacity(double alpha)
     pd->ApplyAppearance(pd->m_Prop);
 }
 
+void Prop3D::GetColor(double &r, double &g, double &b) const
+{
+    r = pd->m_Color[0];
+    g = pd->m_Color[1];
+    b = pd->m_Color[2];
+}
+
+double Prop3D::GetOpacity() const
+{
+    return pd->m_Opacity;
+}
+