0033551: Visualization - Add new transform persistence mode to force orthographic projection on object.

The new transform persistence mode, with flag `Graphic3d_TMF_OrthoPers`, can be combined (bitwise OR operation) with the other persistence modes (2D, Trihedron or Zoom/Rotate Persistence) to make objects be rendered with orthographic projection when it is on a view with perspective projection.

If the view already uses orthographic projection, there will be no difference.

This feature was implemented to fix ViewCube being distorted when view with perspective projection changes size.

src/Graphic3d/Graphic3d_TransModeFlags.hxx

@@ -25,8 +25,15 @@ enum Graphic3d_TransModeFlags
   Graphic3d_TMF_TriedronPers   = 0x0020,                  //!< object behaves like trihedron - it is fixed at the corner of view and does not resizing (but rotating)
   Graphic3d_TMF_2d             = 0x0040,                  //!< object is defined in 2D screen coordinates (pixels) and does not resize, pan and rotate
   Graphic3d_TMF_CameraPers     = 0x0080,                  //!< object is in front of the camera
+  Graphic3d_TMF_OrthoPers      = 0x0100,                  //!< object is forced to be rendered with orthographic projection.
   Graphic3d_TMF_ZoomRotatePers = Graphic3d_TMF_ZoomPers
                                | Graphic3d_TMF_RotatePers //!< object doesn't resize and rotate
 };
 
+//! Bitwise OR operator for transform persistence mode flags. Be aware that some flags combinations are not valid.
+inline Graphic3d_TransModeFlags operator| (Graphic3d_TransModeFlags a, Graphic3d_TransModeFlags b)
+{
+  return static_cast<Graphic3d_TransModeFlags> (static_cast<uint32_t> (a) | static_cast<uint32_t> (b));
+}
+
 #endif

src/Graphic3d/Graphic3d_TransformPers.hxx

@@ -58,6 +58,12 @@ public:
     return (theMode & (Graphic3d_TMF_TriedronPers | Graphic3d_TMF_2d)) != 0;
   }
 
+  //! Return true if specified mode is orthographic projection transformation persistence.
+  static Standard_Boolean IsOrthoPers (Graphic3d_TransModeFlags theMode)
+  {
+    return (theMode & Graphic3d_TMF_OrthoPers) != 0;
+  }
+
 public:
 
   //! Set transformation persistence.
@@ -110,6 +116,9 @@ public:
   //! Return true for Graphic3d_TMF_TriedronPers and Graphic3d_TMF_2d modes.
   Standard_Boolean IsTrihedronOr2d() const { return IsTrihedronOr2d (myMode); }
 
+  //! Return true for Graphic3d_TMF_OrthoPers mode.
+  Standard_Boolean IsOrthoPers () const { return IsOrthoPers (myMode); }
+
   //! Transformation persistence mode flags.
   Graphic3d_TransModeFlags Mode() const { return myMode; }
 
@@ -297,28 +306,32 @@ public:
   //! @param theWorldView [in] the world view transformation matrix.
   //! @param theViewportWidth [in] the width of viewport (for 2d persistence).
   //! @param theViewportHeight [in] the height of viewport (for 2d persistence).
+  //! @param theToApplyProjPers [in] if should apply projection persistence to matrix (for orthographic persistence).
   //! @return transformation matrix to be applied to model world transformation of an object.
   template<class T>
   NCollection_Mat4<T> Compute (const Handle(Graphic3d_Camera)& theCamera,
                                const NCollection_Mat4<T>& theProjection,
                                const NCollection_Mat4<T>& theWorldView,
                                const Standard_Integer theViewportWidth,
-                               const Standard_Integer theViewportHeight) const;
+                               const Standard_Integer theViewportHeight,
+                               const Standard_Boolean theToApplyProjPers = false) const;
 
   //! Apply transformation persistence on specified matrices.
-  //! @param theCamera camera definition
+  //! @param theCamera [in] camera definition
-  //! @param theProjection projection matrix to modify
+  //! @param theProjection [in] projection matrix to modify
-  //! @param theWorldView  world-view matrix to modify
+  //! @param theWorldView [in/out]  world-view matrix to modify
-  //! @param theViewportWidth  viewport width
+  //! @param theViewportWidth [in]  viewport width
-  //! @param theViewportHeight viewport height
+  //! @param theViewportHeight [in] viewport height
-  //! @param theAnchor if not NULL, overrides anchor point
+  //! @param theAnchor [in] if not NULL, overrides anchor point
+  //! @param theToApplyProjPers [in] if should apply projection persistence to matrix (for orthographic persistence).
   template<class T>
   void Apply (const Handle(Graphic3d_Camera)& theCamera,
               const NCollection_Mat4<T>& theProjection,
               NCollection_Mat4<T>& theWorldView,
               const Standard_Integer theViewportWidth,
               const Standard_Integer theViewportHeight,
-              const gp_Pnt* theAnchor = NULL) const;
+              const gp_Pnt* theAnchor = NULL,
+              const Standard_Boolean theToApplyProjPers = true) const;
 
   //! Dumps the content of me into the stream
   Standard_EXPORT virtual void DumpJson (Standard_OStream& theOStream, Standard_Integer theDepth = -1) const;
@@ -368,41 +381,50 @@ void Graphic3d_TransformPers::Apply (const Handle(Graphic3d_Camera)& theCamera,
                                      NCollection_Mat4<T>& theWorldView,
                                      const Standard_Integer theViewportWidth,
                                      const Standard_Integer theViewportHeight,
-                                     const gp_Pnt* theAnchor) const
+                                     const gp_Pnt* theAnchor,
+                                     const Standard_Boolean theToApplyProjPers) const
 {
   (void )theViewportWidth;
-  (void )theProjection;
   if (myMode == Graphic3d_TMF_None
    || theViewportHeight == 0)
   {
     return;
   }
 
+  Handle(Graphic3d_Camera) aCamera = theCamera;
+  if (IsOrthoPers() && !aCamera->IsOrthographic())
+  {
+    aCamera = new Graphic3d_Camera(*theCamera); // If OrthoPers, copy camera and set to orthographic projection
+    aCamera->SetProjectionType (Graphic3d_Camera::Projection_Orthographic);
+  }
+
+  NCollection_Mat4<Standard_Real> aWorldView = aCamera->OrientationMatrix();
+
   // use total size when tiling is active
-  const Standard_Integer aVPSizeY = theCamera->Tile().IsValid() ? theCamera->Tile().TotalSize.y() : theViewportHeight;
+  const Standard_Integer aVPSizeY = aCamera->Tile().IsValid() ? aCamera->Tile().TotalSize.y() : theViewportHeight;
 
   // a small enough jitter compensation offset
   // to avoid image dragging within single pixel in corner cases
   const Standard_Real aJitterComp = 0.001;
-  if (myMode == Graphic3d_TMF_TriedronPers)
+  if ((myMode & Graphic3d_TMF_TriedronPers) != 0)
   {
     // reset Z focus for trihedron persistence
-    const Standard_Real aFocus = theCamera->IsOrthographic()
+    const Standard_Real aFocus = aCamera->IsOrthographic()
-                               ? theCamera->Distance()
+                               ? aCamera->Distance()
-                               : (theCamera->ZFocusType() == Graphic3d_Camera::FocusType_Relative
+                               : (aCamera->ZFocusType() == Graphic3d_Camera::FocusType_Relative
-                                ? Standard_Real(theCamera->ZFocus() * theCamera->Distance())
+                                ? Standard_Real(aCamera->ZFocus() * aCamera->Distance())
-                                : Standard_Real(theCamera->ZFocus()));
+                                : Standard_Real(aCamera->ZFocus()));
 
     // scale factor to pixels
-    const gp_XYZ aViewDim = theCamera->ViewDimensions (aFocus);
+    const gp_XYZ aViewDim = aCamera->ViewDimensions (aFocus);
     const Standard_Real aScale = Abs(aViewDim.Y()) / Standard_Real(aVPSizeY);
-    const gp_Dir aForward = theCamera->Direction();
+    const gp_Dir aForward = aCamera->Direction();
-    gp_XYZ aCenter = theCamera->Center().XYZ() + aForward.XYZ() * (aFocus - theCamera->Distance());
+    gp_XYZ aCenter = aCamera->Center().XYZ() + aForward.XYZ() * (aFocus - aCamera->Distance());
     if ((myParams.Params2d.Corner & (Aspect_TOTP_LEFT | Aspect_TOTP_RIGHT)) != 0)
     {
       const Standard_Real anOffsetX = (Standard_Real(myParams.Params2d.OffsetX) + aJitterComp) * aScale;
-      const gp_Dir aSide   = aForward.Crossed (theCamera->Up());
+      const gp_Dir aSide   = aForward.Crossed (aCamera->Up());
-      const gp_XYZ aDeltaX = aSide.XYZ() * (Abs(aViewDim.X()) * theCamera->NDC2dOffsetX() - anOffsetX);
+      const gp_XYZ aDeltaX = aSide.XYZ() * (Abs(aViewDim.X()) * aCamera->NDC2dOffsetX() - anOffsetX);
       if ((myParams.Params2d.Corner & Aspect_TOTP_RIGHT) != 0)
       {
         aCenter += aDeltaX;
@@ -415,7 +437,7 @@ void Graphic3d_TransformPers::Apply (const Handle(Graphic3d_Camera)& theCamera,
     if ((myParams.Params2d.Corner & (Aspect_TOTP_TOP | Aspect_TOTP_BOTTOM)) != 0)
     {
       const Standard_Real anOffsetY = (Standard_Real(myParams.Params2d.OffsetY) + aJitterComp) * aScale;
-      const gp_XYZ aDeltaY = theCamera->Up().XYZ() * (Abs(aViewDim.Y()) * theCamera->NDC2dOffsetY() - anOffsetY);
+      const gp_XYZ aDeltaY = aCamera->Up().XYZ() * (Abs(aViewDim.Y()) * aCamera->NDC2dOffsetY() - anOffsetY);
       if ((myParams.Params2d.Corner & Aspect_TOTP_TOP) != 0)
       {
         aCenter += aDeltaY;
@@ -426,27 +448,24 @@ void Graphic3d_TransformPers::Apply (const Handle(Graphic3d_Camera)& theCamera,
       }
     }
 
-    NCollection_Mat4<Standard_Real> aWorldView = theCamera->OrientationMatrix();
     Graphic3d_TransformUtils::Translate (aWorldView, aCenter.X(), aCenter.Y(), aCenter.Z());
     Graphic3d_TransformUtils::Scale     (aWorldView, aScale,      aScale,      aScale);
-    theWorldView.ConvertFrom (aWorldView);
-    return;
   }
-  else if (myMode == Graphic3d_TMF_2d)
+  else if ((myMode & Graphic3d_TMF_2d) != 0)
   {
-    const Standard_Real aFocus = theCamera->IsOrthographic()
+    const Standard_Real aFocus = aCamera->IsOrthographic()
-                               ? theCamera->Distance()
+                               ? aCamera->Distance()
-                               : (theCamera->ZFocusType() == Graphic3d_Camera::FocusType_Relative
+                               : (aCamera->ZFocusType() == Graphic3d_Camera::FocusType_Relative
-                                ? Standard_Real(theCamera->ZFocus() * theCamera->Distance())
+                                ? Standard_Real(aCamera->ZFocus() * aCamera->Distance())
-                                : Standard_Real(theCamera->ZFocus()));
+                                : Standard_Real(aCamera->ZFocus()));
 
     // scale factor to pixels
-    const gp_XYZ        aViewDim = theCamera->ViewDimensions (aFocus);
+    const gp_XYZ        aViewDim = aCamera->ViewDimensions (aFocus);
     const Standard_Real aScale   = Abs(aViewDim.Y()) / Standard_Real(aVPSizeY);
     gp_XYZ aCenter (0.0, 0.0, -aFocus);
     if ((myParams.Params2d.Corner & (Aspect_TOTP_LEFT | Aspect_TOTP_RIGHT)) != 0)
     {
-      aCenter.SetX (-aViewDim.X() * theCamera->NDC2dOffsetX() + (Standard_Real(myParams.Params2d.OffsetX) + aJitterComp) * aScale);
+      aCenter.SetX (-aViewDim.X() * aCamera->NDC2dOffsetX() + (Standard_Real(myParams.Params2d.OffsetX) + aJitterComp) * aScale);
       if ((myParams.Params2d.Corner & Aspect_TOTP_RIGHT) != 0)
       {
         aCenter.SetX (-aCenter.X());
@@ -454,26 +473,24 @@ void Graphic3d_TransformPers::Apply (const Handle(Graphic3d_Camera)& theCamera,
     }
     if ((myParams.Params2d.Corner & (Aspect_TOTP_TOP | Aspect_TOTP_BOTTOM)) != 0)
     {
-      aCenter.SetY (-aViewDim.Y() * theCamera->NDC2dOffsetY() + (Standard_Real(myParams.Params2d.OffsetY) + aJitterComp) * aScale);
+      aCenter.SetY (-aViewDim.Y() * aCamera->NDC2dOffsetY() + (Standard_Real(myParams.Params2d.OffsetY) + aJitterComp) * aScale);
       if ((myParams.Params2d.Corner & Aspect_TOTP_TOP) != 0)
       {
         aCenter.SetY (-aCenter.Y());
       }
     }
 
-    theWorldView.InitIdentity();
+    aWorldView.InitIdentity();
-    Graphic3d_TransformUtils::Translate (theWorldView, T(aCenter.X()), T(aCenter.Y()), T(aCenter.Z()));
+    Graphic3d_TransformUtils::Translate (aWorldView, aCenter.X(), aCenter.Y(), aCenter.Z());
-    Graphic3d_TransformUtils::Scale     (theWorldView, T(aScale),      T(aScale),      T(aScale));
+    Graphic3d_TransformUtils::Scale     (aWorldView, aScale,      aScale,      aScale);
-    return;
   }
   else if ((myMode & Graphic3d_TMF_CameraPers) != 0)
   {
-    theWorldView.InitIdentity();
+    aWorldView.InitIdentity();
   }
   else
   {
     // Compute reference point for transformation in untransformed projection space.
-    NCollection_Mat4<Standard_Real> aWorldView = theCamera->OrientationMatrix();
     if (theAnchor != NULL)
     {
       Graphic3d_TransformUtils::Translate (aWorldView, theAnchor->X(), theAnchor->Y(), theAnchor->Z());
@@ -503,12 +520,19 @@ void Graphic3d_TransformPers::Apply (const Handle(Graphic3d_Camera)& theCamera,
     if ((myMode & Graphic3d_TMF_ZoomPers) != 0)
     {
       // lock zooming
-      Standard_Real aScale = persistentScale (theCamera, theViewportWidth, theViewportHeight);
+      Standard_Real aScale = persistentScale (aCamera, theViewportWidth, theViewportHeight);
       Graphic3d_TransformUtils::Scale (aWorldView, aScale, aScale, aScale);
     }
-    theWorldView.ConvertFrom (aWorldView);
-    return;
   }
+
+  if (!theCamera->IsOrthographic() && IsOrthoPers() && theToApplyProjPers)
+  {
+    Graphic3d_Mat4d aProjInv;
+    aProjInv.ConvertFrom (theProjection.Inverted());
+    aWorldView = (aProjInv * aCamera->ProjectionMatrix()) * aWorldView;
+  }
+
+  theWorldView.ConvertFrom (aWorldView);
 }
 
 // =======================================================================
@@ -555,7 +579,7 @@ void Graphic3d_TransformPers::Apply (const Handle(Graphic3d_Camera)& theCamera,
                                      const Standard_Integer theViewportHeight,
                                      BVH_Box<T, 3>& theBoundingBox) const
 {
-  NCollection_Mat4<T> aTPers = Compute (theCamera, theProjection, theWorldView, theViewportWidth, theViewportHeight);
+  NCollection_Mat4<T> aTPers = Compute (theCamera, theProjection, theWorldView, theViewportWidth, theViewportHeight, false);
   if (aTPers.IsIdentity()
   || !theBoundingBox.IsValid())
   {
@@ -594,7 +618,8 @@ NCollection_Mat4<T> Graphic3d_TransformPers::Compute (const Handle(Graphic3d_Cam
                                                       const NCollection_Mat4<T>& theProjection,
                                                       const NCollection_Mat4<T>& theWorldView,
                                                       const Standard_Integer theViewportWidth,
-                                                      const Standard_Integer theViewportHeight) const
+                                                      const Standard_Integer theViewportHeight,
+                                                      const Standard_Boolean theToApplyProjPers) const
 {
   if (myMode == Graphic3d_TMF_None)
   {
@@ -610,7 +635,7 @@ NCollection_Mat4<T> Graphic3d_TransformPers::Compute (const Handle(Graphic3d_Cam
 
   // compute only world-view matrix difference to avoid floating point instability
   // caused by projection matrix modifications outside of this algorithm (e.g. by Z-fit)
-  Apply (theCamera, theProjection, aWorldView, theViewportWidth, theViewportHeight);
+  Apply (theCamera, theProjection, aWorldView, theViewportWidth, theViewportHeight, NULL, theToApplyProjPers);
   return anUnviewMat * aWorldView;
 }
 

src/SelectMgr/SelectMgr_AxisIntersector.cxx

@@ -93,6 +93,24 @@ Handle(SelectMgr_BaseIntersector) SelectMgr_AxisIntersector::ScaleAndTransform (
   return aRes;
 }
 
+//=======================================================================
+// function : CopyWithBuilder
+// purpose  : Returns a copy of the frustum using the given frustum builder configuration.
+//            Returned frustum should be re-constructed before being used.
+//=======================================================================
+Handle(SelectMgr_BaseIntersector) SelectMgr_AxisIntersector::CopyWithBuilder (const Handle(SelectMgr_FrustumBuilder)& theBuilder) const
+{
+  (void )theBuilder;
+  Standard_ASSERT_RAISE(mySelectionType == SelectMgr_SelectionType_Point,
+    "Error! SelectMgr_AxisIntersector::CopyWithBuilder() should be called after selection axis initialization");
+
+  Handle(SelectMgr_AxisIntersector) aRes = new SelectMgr_AxisIntersector();
+  aRes->myAxis = myAxis;
+  aRes->mySelectionType = mySelectionType;
+
+  return aRes;
+}
+
 // =======================================================================
 // function : hasIntersection
 // purpose  :

src/SelectMgr/SelectMgr_AxisIntersector.hxx

@@ -52,6 +52,11 @@ public:
                                                                                const gp_GTrsf& theTrsf,
                                                                                const Handle(SelectMgr_FrustumBuilder)& theBuilder) const Standard_OVERRIDE;
 
+  //! Returns a copy of the intersector transformed using the builder configuration given.
+  //! Builder is an argument that represents corresponding settings for re-constructing transformed frustum from scratch.
+  //! In this class, builder is not used and theBuilder parameter is ignored.
+  Standard_EXPORT virtual Handle(SelectMgr_BaseIntersector) CopyWithBuilder (const Handle(SelectMgr_FrustumBuilder)& theBuilder) const Standard_OVERRIDE;
+
 public:
 
   //! Intersection test between defined axis and given axis-aligned box

src/SelectMgr/SelectMgr_BaseIntersector.hxx

@@ -71,6 +71,11 @@ public:
                                                                const gp_GTrsf& theTrsf,
                                                                const Handle(SelectMgr_FrustumBuilder)& theBuilder) const = 0;
 
+  //! @param theBuilder [in] argument that represents corresponding settings for re-constructing transformed frustum from scratch;
+  //!                        should NOT be NULL.
+  //! @return a copy of the frustum with the input builder assigned
+  virtual Handle(SelectMgr_BaseIntersector) CopyWithBuilder (const Handle(SelectMgr_FrustumBuilder)& theBuilder) const = 0;
+
 public:
 
   //! Return camera definition.

src/SelectMgr/SelectMgr_RectangularFrustum.cxx

@@ -449,6 +449,28 @@ Handle(SelectMgr_BaseIntersector) SelectMgr_RectangularFrustum::ScaleAndTransfor
   return aRes;
 }
 
+// =======================================================================
+// function : CopyWithBuilder
+// purpose  : Returns a copy of the frustum using the given frustum builder configuration.
+//            Returned frustum should be re-constructed before being used.
+// =======================================================================
+Handle(SelectMgr_BaseIntersector) SelectMgr_RectangularFrustum::CopyWithBuilder (const Handle(SelectMgr_FrustumBuilder)& theBuilder) const
+{
+  Standard_ASSERT_RAISE (mySelectionType == SelectMgr_SelectionType_Point || mySelectionType == SelectMgr_SelectionType_Box,
+    "Error! SelectMgr_RectangularFrustum::CopyWithBuilder() should be called after selection frustum initialization");
+
+  Standard_ASSERT_RAISE (!theBuilder.IsNull(), 
+    "Error! SelectMgr_RectangularFrustum::CopyWithBuilder() should be called with valid builder");
+
+  Handle(SelectMgr_RectangularFrustum) aRes = new SelectMgr_RectangularFrustum();
+  aRes->mySelectionType = mySelectionType;
+  aRes->mySelRectangle = mySelRectangle;
+  aRes->myPixelTolerance = myPixelTolerance;
+  aRes->SetBuilder (theBuilder);
+
+  return aRes;
+}
+
 // =======================================================================
 // function : IsScalable
 // purpose  :

src/SelectMgr/SelectMgr_RectangularFrustum.hxx

@@ -99,6 +99,13 @@ public:
                                                                                const gp_GTrsf& theTrsf,
                                                                                const Handle(SelectMgr_FrustumBuilder)& theBuilder) const Standard_OVERRIDE;
 
+  //! Returns a copy of the frustum using the given frustum builder configuration.
+  //! Returned frustum should be re-constructed before being used.
+  //! @param theBuilder [in] argument that represents corresponding settings for re-constructing transformed frustum from scratch;
+  //!                        should NOT be NULL.
+  //! @return a copy of the frustum with the input builder assigned
+  Standard_EXPORT virtual Handle(SelectMgr_BaseIntersector) CopyWithBuilder (const Handle(SelectMgr_FrustumBuilder)& theBuilder) const Standard_OVERRIDE;
+
   // SAT Tests for different objects
 
   //! SAT intersection test between defined volume and given axis-aligned box

src/SelectMgr/SelectMgr_SelectableObjectSet.cxx

@@ -241,17 +241,23 @@ namespace
 //=============================================================================
 SelectMgr_SelectableObjectSet::SelectMgr_SelectableObjectSet()
 {
-  myBVH[BVHSubset_2dPersistent] = new BVH_Tree<Standard_Real, 3>();
+  myBVH[BVHSubset_ortho2dPersistent] = new BVH_Tree<Standard_Real, 3>();
-  myBVH[BVHSubset_3dPersistent] = new BVH_Tree<Standard_Real, 3>();
+  myBVH[BVHSubset_ortho3dPersistent] = new BVH_Tree<Standard_Real, 3>();
-  myBVH[BVHSubset_3d]           = new BVH_Tree<Standard_Real, 3>();
+  myBVH[BVHSubset_2dPersistent]      = new BVH_Tree<Standard_Real, 3>();
+  myBVH[BVHSubset_3dPersistent]      = new BVH_Tree<Standard_Real, 3>();
+  myBVH[BVHSubset_3d]                = new BVH_Tree<Standard_Real, 3>();
 
-  myBuilder[BVHSubset_2dPersistent] = new BVH_LinearBuilder<Standard_Real, 3>    (BVH_Constants_LeafNodeSizeSingle, BVH_Constants_MaxTreeDepth);
+  myBuilder[BVHSubset_ortho2dPersistent] = new BVH_LinearBuilder<Standard_Real, 3>    (BVH_Constants_LeafNodeSizeSingle, BVH_Constants_MaxTreeDepth);
-  myBuilder[BVHSubset_3dPersistent] = new BVH_LinearBuilder<Standard_Real, 3>    (BVH_Constants_LeafNodeSizeSingle, BVH_Constants_MaxTreeDepth);
+  myBuilder[BVHSubset_ortho3dPersistent] = new BVH_LinearBuilder<Standard_Real, 3>    (BVH_Constants_LeafNodeSizeSingle, BVH_Constants_MaxTreeDepth);
-  myBuilder[BVHSubset_3d]           = new BVH_BinnedBuilder<Standard_Real, 3, 4> (BVH_Constants_LeafNodeSizeSingle, BVH_Constants_MaxTreeDepth, Standard_True);
+  myBuilder[BVHSubset_2dPersistent]      = new BVH_LinearBuilder<Standard_Real, 3>    (BVH_Constants_LeafNodeSizeSingle, BVH_Constants_MaxTreeDepth);
+  myBuilder[BVHSubset_3dPersistent]      = new BVH_LinearBuilder<Standard_Real, 3>    (BVH_Constants_LeafNodeSizeSingle, BVH_Constants_MaxTreeDepth);
+  myBuilder[BVHSubset_3d]                = new BVH_BinnedBuilder<Standard_Real, 3, 4> (BVH_Constants_LeafNodeSizeSingle, BVH_Constants_MaxTreeDepth, Standard_True);
 
-  myIsDirty[BVHSubset_2dPersistent] = Standard_False;
+  myIsDirty[BVHSubset_ortho2dPersistent] = Standard_False;
-  myIsDirty[BVHSubset_3dPersistent] = Standard_False;
+  myIsDirty[BVHSubset_ortho3dPersistent] = Standard_False;
-  myIsDirty[BVHSubset_3d]           = Standard_False;
+  myIsDirty[BVHSubset_2dPersistent]      = Standard_False;
+  myIsDirty[BVHSubset_3dPersistent]      = Standard_False;
+  myIsDirty[BVHSubset_3d]                = Standard_False;
 }
 
 //=============================================================================
@@ -262,10 +268,9 @@ Standard_Boolean SelectMgr_SelectableObjectSet::Append (const Handle(SelectMgr_S
 {
   // get an appropriate BVH subset to insert the object into it
   const Standard_Integer aSubsetIdx = appropriateSubset (theObject);
-
+  
   // check that the object is excluded from other subsets
-  if (myObjects[(aSubsetIdx + 1) % BVHSubsetNb].Contains (theObject)
+  if (currentSubset (theObject) != -1)
-   || myObjects[(aSubsetIdx + 2) % BVHSubsetNb].Contains (theObject))
   {
     return Standard_False;
   }
@@ -401,9 +406,51 @@ void SelectMgr_SelectableObjectSet::UpdateBVH (const Handle(Graphic3d_Camera)& t
       myBuilder[BVHSubset_2dPersistent]->Build (&anAdaptor, myBVH[BVHSubset_2dPersistent].get(), anAdaptor.Box());
     }
 
+    // -------------------------------------------------------------------
+    // check and update 3D orthographic persistence BVH tree if necessary
+    // -------------------------------------------------------------------
+    if (!IsEmpty (BVHSubset_ortho3dPersistent)
+      && (myIsDirty[BVHSubset_ortho3dPersistent]
+       || myLastViewState.IsChanged (aViewState)
+       || isWinSizeChanged))
+    {
+      Handle(Graphic3d_Camera) aNewOrthoCam = new Graphic3d_Camera (*theCam); // If OrthoPers, copy camera and set to orthographic projection
+      aNewOrthoCam->SetProjectionType (Graphic3d_Camera::Projection_Orthographic);
+
+      // construct adaptor over private fields to provide direct access for the BVH builder
+      BVHBuilderAdaptorPersistent anAdaptor (myObjects[BVHSubset_ortho3dPersistent],
+                                             aNewOrthoCam, aNewOrthoCam->ProjectionMatrix(), 
+                                             aNewOrthoCam->OrientationMatrix(), theWinSize);
+
+      // update corresponding BVH tree data structure
+      myBuilder[BVHSubset_ortho3dPersistent]->Build (&anAdaptor, myBVH[BVHSubset_ortho3dPersistent].get(), anAdaptor.Box());
+    }
+
+    // -------------------------------------------------------------------
+    // check and update 2D orthographic persistence BVH tree if necessary
+    // -------------------------------------------------------------------
+    if (!IsEmpty (BVHSubset_ortho2dPersistent)
+      && (myIsDirty[BVHSubset_ortho2dPersistent]
+       || myLastViewState.IsProjectionChanged (aViewState)
+       || isWinSizeChanged))
+    {
+      Handle(Graphic3d_Camera) aNewOrthoCam = new Graphic3d_Camera (*theCam); // If OrthoPers, copy camera and set to orthographic projection
+      aNewOrthoCam->SetProjectionType (Graphic3d_Camera::Projection_Orthographic);
+
+      // construct adaptor over private fields to provide direct access for the BVH builder
+      BVHBuilderAdaptorPersistent anAdaptor (myObjects[BVHSubset_ortho2dPersistent],
+                                             aNewOrthoCam, aNewOrthoCam->ProjectionMatrix(), 
+                                             SelectMgr_SelectableObjectSet_THE_IDENTITY_MAT, theWinSize);
+
+      // update corresponding BVH tree data structure
+      myBuilder[BVHSubset_ortho2dPersistent]->Build (&anAdaptor, myBVH[BVHSubset_ortho2dPersistent].get(), anAdaptor.Box());
+    }
+
     // release dirty state for every subset
-    myIsDirty[BVHSubset_3dPersistent] = Standard_False;
+    myIsDirty[BVHSubset_3dPersistent]      = Standard_False;
-    myIsDirty[BVHSubset_2dPersistent] = Standard_False;
+    myIsDirty[BVHSubset_2dPersistent]      = Standard_False;
+    myIsDirty[BVHSubset_ortho3dPersistent] = Standard_False;
+    myIsDirty[BVHSubset_ortho2dPersistent] = Standard_False;
 
     // keep last view state
     myLastViewState = aViewState;
@@ -419,9 +466,11 @@ void SelectMgr_SelectableObjectSet::UpdateBVH (const Handle(Graphic3d_Camera)& t
 //=============================================================================
 void SelectMgr_SelectableObjectSet::MarkDirty()
 {
-  myIsDirty[BVHSubset_3d]           = Standard_True;
+  myIsDirty[BVHSubset_3d]                = Standard_True;
-  myIsDirty[BVHSubset_3dPersistent] = Standard_True;
+  myIsDirty[BVHSubset_3dPersistent]      = Standard_True;
-  myIsDirty[BVHSubset_2dPersistent] = Standard_True;
+  myIsDirty[BVHSubset_2dPersistent]      = Standard_True;
+  myIsDirty[BVHSubset_ortho3dPersistent] = Standard_True;
+  myIsDirty[BVHSubset_ortho2dPersistent] = Standard_True;
 }
 //=======================================================================
 //function : DumpJson

src/SelectMgr/SelectMgr_SelectableObjectSet.hxx

@@ -42,11 +42,22 @@ public:
   //! needs to be updated only when camera's projection changes. Bounding volumes for this object subclass
   //! is represented directly in eye space coordinates.
   //! This subset uses linear BVH builder with 32 levels of depth and 1 element per leaf.
+  //! - BVHSubset_ortho3dPersistent refers to the subset of 3D persistent selectable objects (rotate, pan, zoom persistence)
+  //! that contains `Graphic3d_TMF_OrthoPers` persistence mode.
+  //! Associated BVH tree needs to be updated when either the camera's projection and position change.
+  //! This subset uses linear BVH builder with 32 levels of depth and 1 element per leaf.
+  //! - BVHSubset_ortho2dPersistent refers to the subset of 2D persistent selectable objects
+  //! that contains `Graphic3d_TMF_OrthoPers` persistence mode. Associated BVH tree
+  //! needs to be updated only when camera's projection changes. Bounding volumes for this object subclass
+  //! is represented directly in eye space coordinates.
+  //! This subset uses linear BVH builder with 32 levels of depth and 1 element per leaf.
   enum BVHSubset
   {
     BVHSubset_3d,
     BVHSubset_3dPersistent,
     BVHSubset_2dPersistent,
+    BVHSubset_ortho3dPersistent,
+    BVHSubset_ortho2dPersistent,
     BVHSubsetNb
   };
 
@@ -140,7 +151,9 @@ public:
   {
     return myObjects[BVHSubset_3d].Contains (theObject)
         || myObjects[BVHSubset_3dPersistent].Contains (theObject)
-        || myObjects[BVHSubset_2dPersistent].Contains (theObject);
+        || myObjects[BVHSubset_2dPersistent].Contains (theObject)
+        || myObjects[BVHSubset_ortho3dPersistent].Contains (theObject)
+        || myObjects[BVHSubset_ortho2dPersistent].Contains (theObject);
   }
 
   //! Returns true if the object set does not contain any selectable objects.
@@ -148,7 +161,9 @@ public:
   {
     return myObjects[BVHSubset_3d].IsEmpty()
         && myObjects[BVHSubset_3dPersistent].IsEmpty()
-        && myObjects[BVHSubset_2dPersistent].IsEmpty();
+        && myObjects[BVHSubset_2dPersistent].IsEmpty()
+        && myObjects[BVHSubset_ortho3dPersistent].IsEmpty()
+        && myObjects[BVHSubset_ortho2dPersistent].IsEmpty();
   }
 
   //! Returns true if the specified object subset is empty.
@@ -192,10 +207,18 @@ private:
       }
       return SelectMgr_SelectableObjectSet::BVHSubset_3d;
     }
-    else if (theObject->TransformPersistence()->Mode() == Graphic3d_TMF_2d)
+    else if ((theObject->TransformPersistence()->Mode() & Graphic3d_TMF_2d) != 0)
     {
+      if (theObject->TransformPersistence()->IsOrthoPers())
+      {
+        return SelectMgr_SelectableObjectSet::BVHSubset_ortho2dPersistent;
+      }
       return SelectMgr_SelectableObjectSet::BVHSubset_2dPersistent;
     }
+    else if (theObject->TransformPersistence()->IsOrthoPers())
+    {
+      return SelectMgr_SelectableObjectSet::BVHSubset_ortho3dPersistent;
+    }
     else
     {
       return SelectMgr_SelectableObjectSet::BVHSubset_3dPersistent;

src/SelectMgr/SelectMgr_SelectingVolumeManager.cxx

@@ -67,6 +67,28 @@ SelectMgr_SelectingVolumeManager SelectMgr_SelectingVolumeManager::ScaleAndTrans
   return aMgr;
 }
 
+//=======================================================================
+// function : CopyWithBuilder
+// purpose  : Returns a copy of the selecting volume manager and its active frustum re-constructed using the passed builder.
+//            Builder is an argument that represents corresponding settings for re-constructing transformed
+//            frustum from scratch.
+//=======================================================================
+SelectMgr_SelectingVolumeManager SelectMgr_SelectingVolumeManager::CopyWithBuilder (const Handle(SelectMgr_FrustumBuilder)& theBuilder) const
+{
+  SelectMgr_SelectingVolumeManager aMgr;
+  aMgr.myToAllowOverlap = myToAllowOverlap;
+  aMgr.myViewClipPlanes = myViewClipPlanes;
+  aMgr.myObjectClipPlanes = myObjectClipPlanes;
+  aMgr.myViewClipRange = myViewClipRange;
+  if (!myActiveSelectingVolume.IsNull())
+  {
+    aMgr.myActiveSelectingVolume = myActiveSelectingVolume->CopyWithBuilder (theBuilder);
+    aMgr.BuildSelectingVolume();
+  }
+
+  return aMgr;
+}
+
 //=======================================================================
 // function : GetActiveSelectionType
 // purpose  :

src/SelectMgr/SelectMgr_SelectingVolumeManager.hxx

@@ -81,6 +81,11 @@ public:
                                                                               const gp_GTrsf& theTrsf,
                                                                               const Handle(SelectMgr_FrustumBuilder)& theBuilder) const;
 
+  //! Returns a copy of the selecting volume manager and its active frustum re-constructed using the passed builder.
+  //! Builder is an argument that represents corresponding settings for re-constructing transformed
+  //! frustum from scratch.
+  Standard_EXPORT virtual SelectMgr_SelectingVolumeManager CopyWithBuilder (const Handle(SelectMgr_FrustumBuilder)& theBuilder) const;
+
 public:
 
   //! Returns current camera definition.

src/SelectMgr/SelectMgr_TriangularFrustum.cxx

@@ -189,6 +189,20 @@ Handle(SelectMgr_BaseIntersector) SelectMgr_TriangularFrustum::ScaleAndTransform
   return aRes;
 }
 
+//=======================================================================
+// function : CopyWithBuilder
+// purpose  : Returns a copy of the frustum using the given frustum builder configuration.
+//            Returned frustum should be re-constructed before being used.
+//=======================================================================
+Handle(SelectMgr_BaseIntersector) SelectMgr_TriangularFrustum::CopyWithBuilder (const Handle(SelectMgr_FrustumBuilder)& theBuilder) const
+{
+  Handle(SelectMgr_TriangularFrustum) aRes = new SelectMgr_TriangularFrustum();
+  aRes->mySelTriangle = mySelTriangle;
+  aRes->SetBuilder (theBuilder);
+
+  return aRes;
+}
+
 //=======================================================================
 // function : OverlapsBox
 // purpose  : SAT intersection test between defined volume and

src/SelectMgr/SelectMgr_TriangularFrustum.hxx

@@ -55,6 +55,13 @@ public:
                                                                                const gp_GTrsf& theTrsf,
                                                                                const Handle(SelectMgr_FrustumBuilder)& theBuilder) const Standard_OVERRIDE;
 
+  //! Returns a copy of the frustum using the given frustum builder configuration.
+  //! Returned frustum should be re-constructed before being used.
+  //! @param theBuilder [in] argument that represents corresponding settings for re-constructing transformed frustum from scratch;
+  //!                        should NOT be NULL.
+  //! @return a copy of the frustum with the input builder assigned
+  Standard_EXPORT virtual Handle(SelectMgr_BaseIntersector) CopyWithBuilder (const Handle(SelectMgr_FrustumBuilder)& theBuilder) const Standard_OVERRIDE;
+
 public: //! @name SAT Tests for different objects
 
   //! SAT intersection test between defined volume and given axis-aligned box

src/SelectMgr/SelectMgr_TriangularFrustumSet.cxx

@@ -186,6 +186,32 @@ Handle(SelectMgr_BaseIntersector) SelectMgr_TriangularFrustumSet::ScaleAndTransf
   return aRes;
 }
 
+//=======================================================================
+// function : CopyWithBuilder
+// purpose  : Returns a copy of the frustum using the given frustum builder configuration.
+//            Returned frustum should be re-constructed before being used.
+//=======================================================================
+Handle(SelectMgr_BaseIntersector) SelectMgr_TriangularFrustumSet::CopyWithBuilder (const Handle(SelectMgr_FrustumBuilder)& theBuilder) const
+{
+  Standard_ASSERT_RAISE (mySelectionType == SelectMgr_SelectionType_Polyline,
+    "Error! SelectMgr_TriangularFrustumSet::CopyWithBuilder() should be called after selection frustum initialization");
+
+  Standard_ASSERT_RAISE (!theBuilder.IsNull(), 
+    "Error! SelectMgr_TriangularFrustumSet::CopyWithBuilder() should be called with valid builder");
+
+  Handle(SelectMgr_TriangularFrustumSet) aRes = new SelectMgr_TriangularFrustumSet();
+  aRes->SetCamera (myCamera);
+  for (SelectMgr_TriangFrustums::Iterator anIter (myFrustums); anIter.More(); anIter.Next())
+  {
+    aRes->myFrustums.Append (Handle(SelectMgr_TriangularFrustum)::DownCast (anIter.Value()->CopyWithBuilder (theBuilder)));
+  }
+  aRes->mySelectionType = mySelectionType;
+  aRes->mySelPolyline = mySelPolyline;
+  aRes->myToAllowOverlap = myToAllowOverlap;
+  aRes->SetBuilder (theBuilder);
+  return aRes;
+}
+
 // =======================================================================
 // function : OverlapsBox
 // purpose  :

src/SelectMgr/SelectMgr_TriangularFrustumSet.hxx

@@ -62,6 +62,13 @@ public:
                                                                                const gp_GTrsf& theTrsf,
                                                                                const Handle(SelectMgr_FrustumBuilder)& theBuilder) const Standard_OVERRIDE;
 
+  //! Returns a copy of the frustum using the given frustum builder configuration.
+  //! Returned frustum should be re-constructed before being used.
+  //! @param theBuilder [in] argument that represents corresponding settings for re-constructing transformed frustum from scratch;
+  //!                        should NOT be NULL.
+  //! @return a copy of the frustum with the input builder assigned
+  Standard_EXPORT virtual Handle(SelectMgr_BaseIntersector) CopyWithBuilder (const Handle(SelectMgr_FrustumBuilder)& theBuilder) const Standard_OVERRIDE;
+
 public:
 
   Standard_EXPORT virtual Standard_Boolean OverlapsBox (const SelectMgr_Vec3& theMinPnt,

src/SelectMgr/SelectMgr_ViewerSelector.cxx

@@ -138,12 +138,12 @@ void SelectMgr_ViewerSelector::updatePoint3d (SelectMgr_SortCriterion& theCriter
     case SelectMgr_TypeOfDepthTolerance_UniformPixels:
     case SelectMgr_TypeOfDepthTolerance_SensitivityFactor:
     {
-      if (mySelectingVolumeMgr.Camera().IsNull())
+      if (theMgr.Camera().IsNull())
       {
         // fallback for an arbitrary projection matrix
         theCriterion.Tolerance = aSensFactor / 33.0;
       }
-      else if (mySelectingVolumeMgr.Camera()->IsOrthographic())
+      else if (theMgr.Camera()->IsOrthographic())
       {
         theCriterion.Tolerance = myCameraScale * aSensFactor;
       }
@@ -634,6 +634,9 @@ void SelectMgr_ViewerSelector::TraverseSensitives (const Standard_Integer theVie
 
   Graphic3d_Vec2i aWinSize;
   mySelectingVolumeMgr.WindowSize (aWinSize.x(), aWinSize.y());
+  const double aPixelSize = aWinSize.x() > 0 && aWinSize.y() > 0
+                          ? Max (1.0 / aWinSize.x(), 1.0 / aWinSize.y())
+                          : 1.0;
 
   const Handle(Graphic3d_Camera)& aCamera = mySelectingVolumeMgr.Camera();
   Graphic3d_Mat4d aProjectionMat, aWorldViewMat;
@@ -646,11 +649,6 @@ void SelectMgr_ViewerSelector::TraverseSensitives (const Standard_Integer theVie
 
     myCameraEye = aCamera->Eye().XYZ();
     myCameraDir = aCamera->Direction().XYZ();
-    myCameraScale = aCamera->IsOrthographic()
-                  ? aCamera->Scale()
-                  : 2.0 * Tan (aCamera->FOVy() * M_PI / 360.0);
-    const double aPixelSize = Max (1.0 / aWinSize.x(), 1.0 / aWinSize.y());
-    myCameraScale *= aPixelSize;
   }
   mySelectableObjects.UpdateBVH (aCamera, aWinSize);
 
@@ -672,7 +670,8 @@ void SelectMgr_ViewerSelector::TraverseSensitives (const Standard_Integer theVie
     // for 2D space selection transform selecting volumes to perform overlap testing
     // directly in camera's eye space omitting the camera position, which is not
     // needed there at all
-    if (aBVHSubset == SelectMgr_SelectableObjectSet::BVHSubset_2dPersistent)
+    if (aBVHSubset == SelectMgr_SelectableObjectSet::BVHSubset_2dPersistent 
+     || aBVHSubset == SelectMgr_SelectableObjectSet::BVHSubset_ortho2dPersistent)
     {
       gp_GTrsf aTFrustum;
       aTFrustum.SetValue (1, 1, aWorldViewMat.GetValue (0, 0));
@@ -688,22 +687,46 @@ void SelectMgr_ViewerSelector::TraverseSensitives (const Standard_Integer theVie
                                             aWorldViewMat.GetValue (1, 3),
                                             aWorldViewMat.GetValue (2, 3)));
 
-      // define corresponding frustum builder parameters
+      // define corresponding frustum builder parameters for 2d persistence.
       Handle(SelectMgr_FrustumBuilder) aBuilder = new SelectMgr_FrustumBuilder();
       Handle(Graphic3d_Camera) aNewCamera = new Graphic3d_Camera();
       aNewCamera->CopyMappingData (aCamera);
       aNewCamera->SetIdentityOrientation();
+      if (aBVHSubset == SelectMgr_SelectableObjectSet::BVHSubset_ortho2dPersistent)
+      {
+        aNewCamera->SetProjectionType (Graphic3d_Camera::Projection_Orthographic);
+      }
       aWorldViewMat = aNewCamera->OrientationMatrix(); // should be identity matrix
       aProjectionMat = aNewCamera->ProjectionMatrix(); // should be the same to aProjectionMat
       aBuilder->SetCamera (aNewCamera);
       aBuilder->SetWindowSize (aWinSize.x(), aWinSize.y());
       aMgr = mySelectingVolumeMgr.ScaleAndTransform (1, aTFrustum, aBuilder);
     }
+    else if (aBVHSubset == SelectMgr_SelectableObjectSet::BVHSubset_ortho3dPersistent)
+    {
+      // define corresponding frustum builder parameters for 3d orthographic persistence.
+      Handle(SelectMgr_FrustumBuilder) aBuilder = new SelectMgr_FrustumBuilder();
+      Handle(Graphic3d_Camera) aNewCamera = new Graphic3d_Camera (*aCamera);
+      aNewCamera->SetProjectionType (Graphic3d_Camera::Projection_Orthographic);
+      aWorldViewMat = aNewCamera->OrientationMatrix(); // should be the same to aWorldViewMat
+      aProjectionMat = aNewCamera->ProjectionMatrix(); // should be orthographic projection
+      aBuilder->SetCamera (aNewCamera);
+      aBuilder->SetWindowSize (aWinSize.x(), aWinSize.y());
+      aMgr = mySelectingVolumeMgr.CopyWithBuilder (aBuilder);
+    }
     else
     {
       aMgr = mySelectingVolumeMgr;
     }
 
+    if (!aMgr.Camera().IsNull())
+    {
+      myCameraScale = aMgr.Camera()->IsOrthographic()
+                   ? aMgr.Camera()->Scale()
+                   : 2.0 * Tan (aMgr.Camera()->FOVy() * M_PI / 360.0);
+      myCameraScale *= aPixelSize;
+    }
+
     const opencascade::handle<BVH_Tree<Standard_Real, 3> >& aBVHTree = mySelectableObjects.BVH (aBVHSubset);
 
     Standard_Integer aNode = 0;

src/SelectMgr/SelectMgr_ViewerSelector.hxx

@@ -328,7 +328,7 @@ protected:
   //! @param theObject [in] the selectable object for traversal.
   //! @param theMgr [in] the (un)transformed copy of the selecting volume manager representing active selection frustum.
   //! @param theCamera, theProjectionMat, theWorldViewMat [in] the source camera and matrices for theMgr given.
-  //! @param theViewportWidth, theViewportHeight [in] viewport (window) dimensions for evaluating 
+  //! @param theWinSize [in] viewport (window) dimensions for evaluating 
   //!        object's transformation persistence.
   Standard_EXPORT void traverseObject (const Handle(SelectMgr_SelectableObject)& theObject,
                                        const SelectMgr_SelectingVolumeManager& theMgr,

src/ViewerTest/ViewerTest.cxx

@@ -5100,6 +5100,24 @@ static int VDisplay2 (Draw_Interpretor& theDI,
         aTrsfPers = new Graphic3d_TransformPers (aTrsfPers->Mode(), Aspect_TypeOfTriedronPosition (aCorner), Graphic3d_Vec2i (aZ.IntegerValue()));
       }
     }
+    else if (aNameCase == "-trsfPersOrtho")
+    {
+      if (aTrsfPers.IsNull())
+      {
+        Message::SendFail() << "Error: wrong syntax at " << aName << ".";
+        return 1;
+      }
+
+      toSetTrsfPers = Standard_True;
+      if (aTrsfPers->IsZoomOrRotate())
+      {
+        aTrsfPers = new Graphic3d_TransformPers (aTrsfPers->Mode() | Graphic3d_TMF_OrthoPers, aTrsfPers->AnchorPoint());
+      }
+      else if (aTrsfPers->IsTrihedronOr2d())
+      {
+        aTrsfPers = new Graphic3d_TransformPers (aTrsfPers->Mode() | Graphic3d_TMF_OrthoPers, aTrsfPers->Corner2d(), aTrsfPers->Offset2d());
+      }
+    }
     else if (aNameCase == "-layer"
           || aNameCase == "-zlayer")
     {
@@ -6630,42 +6648,45 @@ If last 3 optional parameters are not set prints numbers of U-, V- isolines and
 
   addCmd ("vdisplay", VDisplay2, /* [vdisplay] */ R"(
 vdisplay [-noupdate|-update] [-mutable] [-neutral]
-         [-trsfPers {zoom|rotate|zoomRotate|none}=none]
+         [-trsfPers {zoom|rotate|zoomRotate|trihedron|none}=none]
             [-trsfPersPos X Y [Z]] [-3d]
             [-2d|-trihedron [{top|bottom|left|right|topLeft
                             |topRight|bottomLeft|bottomRight}
               [offsetX offsetY]]]
+            [-trsfPersOrtho]
          [-dispMode mode] [-highMode mode]
          [-layer index] [-top|-topmost|-overlay|-underlay]
          [-redisplay] [-erased]
          [-noecho] [-autoTriangulation {0|1}]
          name1 [name2] ... [name n]
 Displays named objects.
- -noupdate    Suppresses viewer redraw call.
+ -noupdate      Suppresses viewer redraw call.
- -mutable     Enables optimizations for mutable objects.
+ -mutable       Enables optimizations for mutable objects.
- -neutral     Draws objects in main viewer.
+ -neutral       Draws objects in main viewer.
- -erased      Loads the object into context, but does not display it.
+ -erased        Loads the object into context, but does not display it.
- -layer       Sets z-layer for objects.
+ -layer         Sets z-layer for objects.
-              Alternatively -overlay|-underlay|-top|-topmost
+                Alternatively -overlay|-underlay|-top|-topmost
-              options can be used for the default z-layers.
+                options can be used for the default z-layers.
- -top         Draws object on top of main presentations
+ -top           Draws object on top of main presentations
-              but below topmost.
+                but below topmost.
- -topmost     Draws in overlay for 3D presentations.
+ -topmost       Draws in overlay for 3D presentations.
-              with independent Depth.
+                with independent Depth.
- -overlay     Draws objects in overlay for 2D presentations.
+ -overlay       Draws objects in overlay for 2D presentations.
-              (On-Screen-Display)
+                (On-Screen-Display)
- -underlay    Draws objects in underlay for 2D presentations.
+ -underlay      Draws objects in underlay for 2D presentations.
-              (On-Screen-Display)
+                (On-Screen-Display)
  -selectable|-noselect Controls selection of objects.
- -trsfPers    Sets a transform persistence flags.
+ -trsfPers      Sets a transform persistence flags.
- -trsfPersPos Sets an anchor point for transform persistence.
+ -trsfPersPos   Sets an anchor point for transform persistence.
- -2d          Displays object in screen coordinates.
+ -2d            Displays object in screen coordinates.
-              (DY looks up)
+                (DY looks up)
- -dispmode    Sets display mode for objects.
+ -trsfPersOrtho Set orthographic transform persistence.
- -highmode    Sets hilight mode for objects.
+                (Objects shown with orthographic projection)
- -redisplay   Recomputes presentation of objects.
+ -dispmode      Sets display mode for objects.
- -noecho      Avoid printing of command results.
+ -highmode      Sets hilight mode for objects.
- -autoTriang  Enable/disable auto-triangulation for displayed shape.
+ -redisplay     Recomputes presentation of objects.
+ -noecho        Avoid printing of command results.
+ -autoTriang    Enable/disable auto-triangulation for displayed shape.
 )" /* [vdisplay] */);
 
   addCmd ("vnbdisplayed", VNbDisplayed, /* [vnbdisplayed] */ R"(

src/ViewerTest/ViewerTest_ViewerCommands.cxx

@@ -13686,6 +13686,12 @@ static int VViewCube (Draw_Interpretor& ,
     {
       aViewCube->SetAxesSphereRadius (Draw::Atof (theArgVec[++anArgIter]));
     }
+    else if (anArg == "-orthopers")
+    {
+      const Handle(Graphic3d_TransformPers)& aTrsfPers = aViewCube->TransformPersistence();
+      Handle(Graphic3d_TransformPers) anOrthoPers = new Graphic3d_TransformPers (Graphic3d_TMF_TriedronPers | Graphic3d_TMF_OrthoPers, aTrsfPers->Corner2d(), aTrsfPers->Offset2d());
+      aViewCube->SetTransformPersistence (anOrthoPers);
+    }
     else
     {
       Message::SendFail() << "Syntax error: unknown argument '" << anArg << "'";
@@ -14983,6 +14989,7 @@ Displays interactive view manipulation object. Options:
  -axesSphereRadius Value  radius of the sphere (central point) of trihedron
  -fixedAnimation {0|1}    uninterruptible animation loop
  -duration Seconds        animation duration in seconds
+ -orthoPers               force orthographic projection persistence.
 )" /* [vviewcube] */);
 
   addCmd ("vcolorconvert", VColorConvert, /* [vcolorconvert] */ R"(

tests/v3d/viewcube/orthopers

@@ -0,0 +1,37 @@
+puts "=================================="
+puts "0028954: Visualization - compare AIS_ViewCube on perspective view with and without orthographic persistence"
+puts "=================================="
+
+pload MODELING VISUALIZATION
+vclear
+vinit View1
+vcamera -persp
+
+box b 15 20 70
+vdisplay -dispMode 1 b
+vaxo
+vfit
+vviewcube vc -fixedAnimation 1 -duration 0 -orthoPers
+
+vmoveto 70 350
+if {[vreadpixel 95 350 name rgb] != "GRAY62"} { puts "Error: Highlighting of view cube Side is wrong." }
+vmoveto 0 0
+vdump $imagedir/${casename}_axo.png
+
+# check FRONT side
+vselect 70 340
+if {[vreadpixel 255 300 name rgb] != "BLACK"} { puts "Error: Position of FRONT camera is wrong." }
+vdump $imagedir/${casename}_side.png
+
+# check FRONT/TOP edge
+vselect 110 270
+if {[vreadpixel 100 320 name rgb] != "GRAY57"} { puts "Error: Position of FRONT-TOP camera is wrong." }
+if {[vreadpixel 100 310 name rgb] != "CYAN"}   { puts "Error: Position of FRONT-TOP camera is wrong." }
+vdump $imagedir/${casename}_edge.png
+
+# Check vertex
+vselect 140 310
+if {[vreadpixel 100 290 name rgb] != "GRAY41"} { puts "Error: Position of TOP-FRONT-RIGHT camera is wrong." }
+if {[vreadpixel 100 310 name rgb] != "CYAN"}   { puts "Error: Position of TOP-FRONT-RIGHT camera is wrong." }
+if {[vreadpixel 100 320 name rgb] != "GRAY62"} { puts "Error: Position of TOP-FRONT-RIGHT camera is wrong." }
+vdump $imagedir/${casename}_corner.png