0031373: Samples - provide sample combining OCCT and 3 viewer

OpenGl_Context::BindTextures() now iterates over pair of texture sets
considering inconsistent texture unit ranges.

adm/cmake/qt.cmake

@@ -7,7 +7,8 @@ if (NOT DEFINED ${3RDPARTY_QT_DIR} AND ${3RDPARTY_QT_DIR} STREQUAL "")
   FIND_PRODUCT_DIR ("${3RDPARTY_DIR}" Qt 3RDPARTY_QT_DIR_NAME)
 
   if (NOT DEFINED ${3RDPARTY_QT_DIR_NAME} AND ${3RDPARTY_QT_DIR_NAME} STREQUAL "")
-    message (FATAL_ERROR "... Qt root directory was not found")
+    set (3RDPARTY_QT_DIR "" CACHE PATH "The directory containing qt")
+    message (FATAL_ERROR "Could not find used third-party product: 3RDPARTY_QT_DIR")
   endif()
 
   # Combine directory name with absolute path and show in GUI
@@ -31,4 +32,10 @@ if (NOT ${Qt5_FOUND})
   #message (STATUS "Qt4 cmake configuration")
 else()
   #message (STATUS "Qt5 cmake configuration")
-endif()
+endif()
+
+if (3RDPARTY_QT_DIR OR EXISTS "${3RDPARTY_QT_DIR}")
+  list (APPEND 3RDPARTY_DLL_DIRS "${3RDPARTY_QT_DIR}/bin")
+else()
+  list (APPEND 3RDPARTY_NO_DLLS 3RDPARTY_QT_DLL_DIR)
+endif()

samples/webgl/WasmOcctView.cpp

@@ -52,6 +52,14 @@ namespace
     return aDevicePixelRatio;
   });
 
+  /*EM_JS(void, jsSetOcctCamera, (float theFOV, float theAspect, float theNear, float theFar), {
+    setOcctCamera();
+  });*/
+
+  EM_JS(void, jsPostFrameRender, (), {
+    postFrameRender();
+  });
+
   //! Return cavas size in pixels.
   static Graphic3d_Vec2i jsCanvasSize()
   {
@@ -336,7 +344,13 @@ void WasmOcctView::handleViewRedraw (const Handle(AIS_InteractiveContext)& theCt
                                      const Handle(V3d_View)& theView)
 {
   myUpdateRequests = 0;
+
+  theView->Invalidate(); /// Three.js cannot be rendered properly without full redraw
+  glEnable (GL_POLYGON_OFFSET_FILL); /// reset defaults Graphic3d_PolygonOffset after Three.js
+  glPolygonOffset (1.0f, 1.0f);
+
   AIS_ViewController::handleViewRedraw (theCtx, theView);
+  jsPostFrameRender();
   if (myToAskNextFrame)
   {
     // ask more frames

samples/webgl/main.cpp

@@ -4,6 +4,7 @@
 
 #include <Message.hxx>
 #include <Message_Messenger.hxx>
+#include <Message_PrinterSystemLog.hxx>
 #include <OSD_MemInfo.hxx>
 #include <OSD_Parallel.hxx>
 
@@ -56,6 +57,8 @@ static void onFileReadFailed (void* theOpaque)
 int main()
 {
   Message::DefaultMessenger()->Printers().First()->SetTraceLevel (Message_Trace);
+  Handle(Message_PrinterSystemLog) aJSConsolePrinter = new Message_PrinterSystemLog ("webgl-sample", Message_Trace);
+  Message::DefaultMessenger()->AddPrinter (aJSConsolePrinter); // open JavaScript console within the Browser to see this output
   Message::DefaultMessenger()->Send (TCollection_AsciiString("NbLogicalProcessors: ") + OSD_Parallel::NbLogicalProcessors(), Message_Trace);
   aViewer.run();
   Message::DefaultMessenger()->Send (OSD_MemInfo::PrintInfo(), Message_Trace);

samples/webgl/occt-webgl-sample.html

@@ -16,6 +16,7 @@
 <div><label for="fileInput">Choose BREP file to upload: </label><input type="file" id="fileInput" accept=".brep"></div>
 <h4>Console output:</h4>
 <p id="output"></p>
+<script src="three.min.js"></script>
 <script>
 //! Resize canvas to fit into window.
 function updateCanvasSize()
@@ -57,6 +58,7 @@ if (!isWasmSupported())
 {
   var anElement = document.getElementById('output');
   anElement.innerHTML += "Browser is too old - WebAssembly support is missing!<br>Please check updates or install a modern browser.<br>";
+  throw new Error();
 }
 
 //! Define OCCT WebGL Viewer module.
@@ -76,6 +78,44 @@ var Module =
   })()
 };
 
+var aCanvas = document.getElementById ('canvas');
+var aGlCtx  = aCanvas.getContext ('webgl2', { alpha: false, depth: true, antialias: false, preserveDrawingBuffer: true } );
+if (aGlCtx == null)
+{
+  aGlCtx    = aCanvas.getContext ('webgl',  { alpha: false, depth: true, antialias: false, preserveDrawingBuffer: true } );
+}
+var aScene  = new THREE.Scene();
+var aCamera = new THREE.PerspectiveCamera (75, window.innerWidth / window.innerHeight);
+//var aRenderer = new THREE.WebGLRenderer ({antialias: true});
+var aRenderer = new THREE.WebGLRenderer ({antialias: false, canvas: aCanvas, context: aGlCtx});
+aRenderer.autoClear = false;
+aRenderer.autoClearColor = false;
+aRenderer.autoClearDepth = false;
+aRenderer.autoClearStencil = false;
+aRenderer.setSize (window.innerWidth,window.innerHeight);
+//document.body.appendChild (aRenderer.domElement);
+var aGeom = new THREE.BoxGeometry (1,1,1);
+var aMat  = new THREE.MeshBasicMaterial ({color: 0xff0000});
+var aCube = new THREE.Mesh (aGeom, aMat);
+aScene.add (aCube);
+aCube.position.z = -5; aCube.rotation.x = 10; aCube.rotation.y = 5;
+/*aRenderer.render (aScene, aCamera);
+var anAnimate = function(){
+  aCube.rotation.x += 0.01;
+  aRenderer.state.reset();
+  aRenderer.render (aScene, aCamera);
+  requestAnimationFrame (anAnimate);
+}
+anAnimate();*/
+
+function postFrameRender()
+{
+  //console.log("postFrameRender()"); ///
+  //aCamera.
+  aRenderer.state.reset();
+  aRenderer.render (aScene, aCamera)
+}
+
 //! Handle file uploading.
 fileInput.onchange = function()
 {

src/AIS/AIS_InteractiveContext.cxx

@@ -2554,15 +2554,6 @@ void AIS_InteractiveContext::SetTransformPersistence (const Handle(AIS_Interacti
                                                       const Handle(Graphic3d_TransformPers)& theTrsfPers)
 {
   theObject->SetTransformPersistence (theTrsfPers);
-  UpdateOnTransformPersistence (theObject);
-}
-
-//=======================================================================
-//function : UpdateOnTransformPersistence
-//purpose  :
-//=======================================================================
-void AIS_InteractiveContext::UpdateOnTransformPersistence (const Handle(AIS_InteractiveObject)& theObject)
-{
   if (!myObjects.IsBound (theObject))
   {
     return;

src/AIS/AIS_InteractiveContext.hxx

@@ -344,11 +344,6 @@ public: //! @name object local transformation management
   Standard_EXPORT void SetTransformPersistence (const Handle(AIS_InteractiveObject)& theObject,
                                                 const Handle(Graphic3d_TransformPers)& theTrsfPers);
 
-  //! Updates displayed interactive object by checking and recomputing its flagged as "to be recomputed" presentation and selection structures.
-  //! This method does not force any recomputation on its own.
-  //! The method recomputes selections even if they are loaded without activation in particular selector.
-  Standard_EXPORT void UpdateOnTransformPersistence (const Handle(AIS_InteractiveObject)& theIObj);
-
   Standard_DEPRECATED("This method is deprecated - SetTransformPersistence() taking Graphic3d_TransformPers should be called instead")
   void SetTransformPersistence (const Handle(AIS_InteractiveObject)& theObj,
                                 const Graphic3d_TransModeFlags&      theFlag,

src/AIS/AIS_InteractiveObject.cxx

@@ -83,17 +83,6 @@ void AIS_InteractiveObject::SetContext (const Handle(AIS_InteractiveContext)& th
   }
 }
 
-//-----------------------------------------------------------------------------
-void AIS_InteractiveObject::SetTransformPersistence (const Handle(Graphic3d_TransformPers)& theTrsfPers)
-{
-  SelectMgr_SelectableObject::SetTransformPersistence (theTrsfPers);
-
-  if (!GetContext().IsNull())
-  {
-    GetContext()->UpdateOnTransformPersistence (this);
-  }
-}
-
 //=======================================================================
 //function : HasPresentation
 //purpose  :

src/AIS/AIS_InteractiveObject.hxx

@@ -108,11 +108,6 @@ public:
   //! Returns the context pointer to the interactive context.
   Standard_EXPORT Handle(AIS_InteractiveContext) GetContext() const;
 
-  //! Sets up Transform Persistence defining a special Local Coordinate system where this object should be located.
-  //! Updates the presentation in context if it is not NULL
-  //! @sa Graphic3d_TransformPers class description
-  Standard_EXPORT virtual void SetTransformPersistence (const Handle(Graphic3d_TransformPers)& theTrsfPers);
-
   //! Returns TRUE when this object has a presentation in the current DisplayMode()
   Standard_EXPORT Standard_Boolean HasPresentation() const;
 

src/Graphic3d/Graphic3d_TextureSet.hxx

@@ -18,6 +18,7 @@
 #include <NCollection_Array1.hxx>
 
 //! Class holding array of textures to be mapped as a set.
+//! Textures should be defined in ascending order of texture units within the set.
 class Graphic3d_TextureSet : public Standard_Transient
 {
   DEFINE_STANDARD_RTTIEXT(Graphic3d_TextureSet, Standard_Transient)

src/Message/Message_PrinterOStream.cxx

@@ -243,6 +243,12 @@ void Message_PrinterOStream::SetConsoleTextColor (Standard_OStream* theOStream,
     }
     SetConsoleTextAttribute (anStdOut, aFlags);
   }
+#elif defined(__EMSCRIPTEN__)
+  // Terminal capabilities are undefined on this platform.
+  // std::cout could be redirected to HTML page, into terminal or somewhere else.
+  (void )theOStream;
+  (void )theTextColor;
+  (void )theIsIntenseText;
 #else
   if (theOStream == NULL)
   {

src/Message/Message_PrinterSystemLog.cxx

@@ -54,6 +54,35 @@
     }
     return ANDROID_LOG_DEBUG;
   }
+#elif defined(__EMSCRIPTEN__)
+  #include <emscripten/emscripten.h>
+
+  // actual version of Emscripten does not define these yet
+  #ifndef EM_LOG_INFO
+    #define EM_LOG_INFO 0
+  #endif
+  #ifndef EM_LOG_DEBUG
+    #define EM_LOG_DEBUG 0
+  #endif
+
+  //! Convert message gravity into emscripten_log() flags.
+  static int getEmscriptenPriority (const Message_Gravity theGravity)
+  {
+    switch (theGravity)
+    {
+      case Message_Trace:   return EM_LOG_CONSOLE | EM_LOG_DEBUG;
+      case Message_Info:    return EM_LOG_CONSOLE | EM_LOG_INFO;
+      case Message_Warning: return EM_LOG_CONSOLE | EM_LOG_WARN;
+      case Message_Alarm:   return EM_LOG_CONSOLE | EM_LOG_ERROR;
+      case Message_Fail:    return EM_LOG_CONSOLE | EM_LOG_ERROR;
+    }
+    return EM_LOG_CONSOLE;
+  }
+
+  //! Print message to console.debug().
+  EM_JS(void, debugMsgToConsole, (const char* theStr), {
+    console.debug(UTF8ToString(theStr));
+  });
 #else
   #include <syslog.h>
 
@@ -90,6 +119,8 @@ Message_PrinterSystemLog::Message_PrinterSystemLog (const TCollection_AsciiStrin
   myEventSource = (Standard_Address )RegisterEventSourceW (NULL, aWideSrcName.ToWideString());
 #elif defined(__ANDROID__)
   //
+#elif defined(__EMSCRIPTEN__)
+  //
 #else
   openlog (myEventSourceName.ToCString(), LOG_PID | LOG_NDELAY, LOG_USER);
 #endif
@@ -110,6 +141,8 @@ Message_PrinterSystemLog::~Message_PrinterSystemLog()
   }
 #elif defined(__ANDROID__)
   //
+#elif defined(__EMSCRIPTEN__)
+  //
 #else
   closelog();
 #endif
@@ -132,6 +165,15 @@ void Message_PrinterSystemLog::Send (const Standard_CString theString,
   Send (TCollection_ExtendedString (theString), theGravity, true);
 #elif defined(__ANDROID__)
   __android_log_write (getAndroidLogPriority (theGravity), myEventSourceName.ToCString(), theString);
+#elif defined(__EMSCRIPTEN__)
+  if (theGravity == Message_Trace)
+  {
+    debugMsgToConsole (theString);
+  }
+  else
+  {
+    emscripten_log (getEmscriptenPriority (theGravity), "%s", theString);
+  }
 #else
   syslog (getSysLogPriority (theGravity), "%s", theString);
 #endif
@@ -154,6 +196,15 @@ void Message_PrinterSystemLog::Send (const TCollection_AsciiString& theString,
   Send (TCollection_ExtendedString (theString), theGravity, true);
 #elif defined(__ANDROID__)
   __android_log_write (getAndroidLogPriority (theGravity), myEventSourceName.ToCString(), theString.ToCString());
+#elif defined(__EMSCRIPTEN__)
+  if (theGravity == Message_Trace)
+  {
+    debugMsgToConsole (theString.ToCString());
+  }
+  else
+  {
+    emscripten_log (getEmscriptenPriority (theGravity), "%s", theString.ToCString());
+  }
 #else
   syslog (getSysLogPriority (theGravity), "%s", theString.ToCString());
 #endif

src/OpenGl/FILES

@@ -56,6 +56,7 @@ OpenGl_TextureFormat.cxx
 OpenGl_TextureFormat.hxx
 OpenGl_TextureSet.cxx
 OpenGl_TextureSet.hxx
+OpenGl_TextureSetPairIterator.hxx
 OpenGl_Resource.hxx
 OpenGl_Resource.cxx
 OpenGl_NamedResource.hxx

src/OpenGl/OpenGl_AspectsTextureSet.cxx

@@ -195,6 +195,7 @@ void OpenGl_AspectsTextureSet::build (const Handle(OpenGl_Context)& theCtx,
 
   Standard_Integer& aTextureSetBits = myTextures[0]->ChangeTextureSetBits();
   aTextureSetBits = Graphic3d_TextureSetBits_NONE;
+  Standard_Integer aPrevTextureUnit = -1;
   if (theAspect->ToMapTexture())
   {
     Graphic3d_TextureSet::Iterator aTextureIter (aNewTextureSet);
@@ -212,6 +213,11 @@ void OpenGl_AspectsTextureSet::build (const Handle(OpenGl_Context)& theCtx,
           if (aResource->Init(theCtx, aTexture))
           {
             aResIter0.ChangeUnit() = aResource->Sampler()->Parameters()->TextureUnit();
+            if (aResIter0.Unit() < aPrevTextureUnit)
+            {
+              throw Standard_ProgramError("Graphic3d_TextureMap defines texture units in non-ascending order");
+            }
+            aPrevTextureUnit = aResIter0.Unit();
             aResource->Sampler()->SetParameters(aTexture->GetParams());
             aResource->SetRevision (aTexture->Revision());
           }
@@ -262,6 +268,11 @@ void OpenGl_AspectsTextureSet::build (const Handle(OpenGl_Context)& theCtx,
         // update occupation of texture units
         const Graphic3d_TextureUnit aTexUnit = aResource->Sampler()->Parameters()->TextureUnit();
         aResIter0.ChangeUnit() = aTexUnit;
+        if (aResIter0.Unit() < aPrevTextureUnit)
+        {
+          throw Standard_ProgramError("Graphic3d_TextureMap defines texture units in non-ascending order");
+        }
+        aPrevTextureUnit = aResIter0.Unit();
         if (aTexUnit >= Graphic3d_TextureUnit_0 && aTexUnit <= Graphic3d_TextureUnit_5)
         {
           aTextureSetBits |= (1 << int(aTexUnit));

src/OpenGl/OpenGl_Context.cxx

@@ -31,6 +31,7 @@
 #include <OpenGl_FrameStats.hxx>
 #include <OpenGl_Sampler.hxx>
 #include <OpenGl_ShaderManager.hxx>
+#include <OpenGl_TextureSetPairIterator.hxx>
 #include <OpenGl_Workspace.hxx>
 #include <OpenGl_Aspects.hxx>
 #include <Graphic3d_TransformUtils.hxx>
@@ -1044,32 +1045,47 @@ void OpenGl_Context::ReadGlVersion (Standard_Integer& theGlVerMajor,
   theGlVerMajor = 0;
   theGlVerMinor = 0;
 
-#ifdef GL_MAJOR_VERSION
-  // available since OpenGL 3.0 and OpenGL 3.0 ES
-  GLint aMajor = 0, aMinor = 0;
-  glGetIntegerv (GL_MAJOR_VERSION, &aMajor);
-  glGetIntegerv (GL_MINOR_VERSION, &aMinor);
-  // glGetError() sometimes does not report an error here even if
-  // GL does not know GL_MAJOR_VERSION and GL_MINOR_VERSION constants.
-  // This happens on some renderers like e.g. Cygwin MESA.
-  // Thus checking additionally if GL has put anything to
-  // the output variables.
-  if (::glGetError() == GL_NO_ERROR && aMajor != 0 && aMinor != 0)
+  bool toCheckVer3 = true;
+#if defined(__EMSCRIPTEN__)
+  // WebGL 1.0 prints annoying invalid enumeration warnings to console.
+  toCheckVer3 = false;
+  if (EMSCRIPTEN_WEBGL_CONTEXT_HANDLE aWebGlCtx = emscripten_webgl_get_current_context())
   {
-    theGlVerMajor = aMajor;
-    theGlVerMinor = aMinor;
-    return;
-  }
-  for (GLenum anErr = ::glGetError(), aPrevErr = GL_NO_ERROR;; aPrevErr = anErr, anErr = ::glGetError())
-  {
-    if (anErr == GL_NO_ERROR
-     || anErr == aPrevErr)
+    EmscriptenWebGLContextAttributes anAttribs = {};
+    if (emscripten_webgl_get_context_attributes (aWebGlCtx, &anAttribs) == EMSCRIPTEN_RESULT_SUCCESS)
     {
-      break;
+      toCheckVer3 = anAttribs.majorVersion >= 2;
     }
   }
 #endif
 
+  // Available since OpenGL 3.0 and OpenGL ES 3.0.
+  if (toCheckVer3)
+  {
+    GLint aMajor = 0, aMinor = 0;
+    glGetIntegerv (GL_MAJOR_VERSION, &aMajor);
+    glGetIntegerv (GL_MINOR_VERSION, &aMinor);
+    // glGetError() sometimes does not report an error here even if
+    // GL does not know GL_MAJOR_VERSION and GL_MINOR_VERSION constants.
+    // This happens on some renderers like e.g. Cygwin MESA.
+    // Thus checking additionally if GL has put anything to
+    // the output variables.
+    if (::glGetError() == GL_NO_ERROR && aMajor != 0 && aMinor != 0)
+    {
+      theGlVerMajor = aMajor;
+      theGlVerMinor = aMinor;
+      return;
+    }
+    for (GLenum anErr = ::glGetError(), aPrevErr = GL_NO_ERROR;; aPrevErr = anErr, anErr = ::glGetError())
+    {
+      if (anErr == GL_NO_ERROR
+       || anErr == aPrevErr)
+      {
+        break;
+      }
+    }
+  }
+
   // Read version string.
   // Notice that only first two numbers split by point '2.1 XXXXX' are significant.
   // Following trash (after space) is vendor-specific.
@@ -3413,93 +3429,56 @@ Handle(OpenGl_TextureSet) OpenGl_Context::BindTextures (const Handle(OpenGl_Text
   if (myActiveTextures != theTextures)
   {
     Handle(OpenGl_Context) aThisCtx (this);
-    OpenGl_TextureSet::Iterator aTextureIterOld (myActiveTextures), aTextureIterNew (theTextures);
-    for (;;)
+    for (OpenGl_TextureSetPairIterator aSlotIter (myActiveTextures, theTextures); aSlotIter.More(); aSlotIter.Next())
     {
-      if (!aTextureIterNew.More())
+      const Graphic3d_TextureUnit aTexUnit = aSlotIter.Unit();
+      const OpenGl_Texture* aTextureOld = aSlotIter.Texture1();
+      const OpenGl_Texture* aTextureNew = aSlotIter.Texture2();
+      if (aTextureNew == aTextureOld)
       {
-        for (; aTextureIterOld.More(); aTextureIterOld.Next())
-        {
-          if (const Handle(OpenGl_Texture)& aTextureOld = aTextureIterOld.Value())
-          {
-            aTextureOld->Unbind (aThisCtx, aTextureIterOld.Unit());
-          #if !defined(GL_ES_VERSION_2_0)
-            if (core11 != NULL)
-            {
-              OpenGl_Sampler::resetGlobalTextureParams (aThisCtx, *aTextureOld, aTextureOld->Sampler()->Parameters());
-            }
-          #endif
-          }
-        }
-        break;
-      }
-
-      const Handle(OpenGl_Texture)& aTextureNew = aTextureIterNew.Value();
-      if (aTextureIterOld.More())
-      {
-        const Handle(OpenGl_Texture)& aTextureOld = aTextureIterOld.Value();
-        if (aTextureNew == aTextureOld
-         && aTextureIterNew.Unit() == aTextureIterOld.Unit())
-        {
-          aTextureIterNew.Next();
-          aTextureIterOld.Next();
-          continue;
-        }
-        else if (aTextureNew.IsNull()
-             || !aTextureNew->IsValid())
-        {
-          if (!aTextureOld.IsNull())
-          {
-            aTextureOld->Unbind (aThisCtx, aTextureIterOld.Unit());
-          #if !defined(GL_ES_VERSION_2_0)
-            if (core11 != NULL)
-            {
-              OpenGl_Sampler::resetGlobalTextureParams (aThisCtx, *aTextureOld, aTextureOld->Sampler()->Parameters());
-            }
-          #endif
-          }
-
-          aTextureIterNew.Next();
-          aTextureIterOld.Next();
-          continue;
-        }
-
-        aTextureIterOld.Next();
-      }
-      if (aTextureNew.IsNull())
-      {
-        aTextureIterNew.Next();
         continue;
       }
 
-      const Graphic3d_TextureUnit aTexUnit = aTextureIterNew.Unit();
-      if (aTexUnit >= myMaxTexCombined)
+      if (aTextureNew != NULL
+       && aTextureNew->IsValid())
       {
-        PushMessage (GL_DEBUG_SOURCE_APPLICATION, GL_DEBUG_TYPE_ERROR, 0, GL_DEBUG_SEVERITY_HIGH,
-                     TCollection_AsciiString("Texture unit ") + aTexUnit + " for " + aTextureNew->ResourceId() + " exceeds hardware limit " + myMaxTexCombined);
-        aTextureIterNew.Next();
-        continue;
-      }
+        if (aTexUnit >= myMaxTexCombined)
+        {
+          PushMessage (GL_DEBUG_SOURCE_APPLICATION, GL_DEBUG_TYPE_ERROR, 0, GL_DEBUG_SEVERITY_HIGH,
+                       TCollection_AsciiString("Texture unit ") + aTexUnit + " for " + aTextureNew->ResourceId() + " exceeds hardware limit " + myMaxTexCombined);
+          continue;
+        }
 
-      aTextureNew->Bind (aThisCtx, aTexUnit);
-      if (aTextureNew->Sampler()->ToUpdateParameters())
-      {
-        if (aTextureNew->Sampler()->IsImmutable())
+        aTextureNew->Bind (aThisCtx, aTexUnit);
+        if (aTextureNew->Sampler()->ToUpdateParameters())
         {
-          aTextureNew->Sampler()->Init (aThisCtx, *aTextureNew);
+          if (aTextureNew->Sampler()->IsImmutable())
+          {
+            aTextureNew->Sampler()->Init (aThisCtx, *aTextureNew);
+          }
+          else
+          {
+            OpenGl_Sampler::applySamplerParams (aThisCtx, aTextureNew->Sampler()->Parameters(), aTextureNew->Sampler().get(), aTextureNew->GetTarget(), aTextureNew->HasMipmaps());
+          }
         }
-        else
+      #if !defined(GL_ES_VERSION_2_0)
+        if (core11 != NULL)
         {
-          OpenGl_Sampler::applySamplerParams (aThisCtx, aTextureNew->Sampler()->Parameters(), aTextureNew->Sampler().get(), aTextureNew->GetTarget(), aTextureNew->HasMipmaps());
+          OpenGl_Sampler::applyGlobalTextureParams (aThisCtx, *aTextureNew, aTextureNew->Sampler()->Parameters());
         }
+      #endif
       }
-    #if !defined(GL_ES_VERSION_2_0)
-      if (core11 != NULL)
+      else if (aTextureOld != NULL
+            && aTextureOld->IsValid())
       {
-        OpenGl_Sampler::applyGlobalTextureParams (aThisCtx, *aTextureNew, aTextureNew->Sampler()->Parameters());
+        aTextureOld->Unbind (aThisCtx, aTexUnit);
+      #if !defined(GL_ES_VERSION_2_0)
+        if (core11 != NULL)
+        {
+          OpenGl_Sampler::resetGlobalTextureParams (aThisCtx, *aTextureOld, aTextureOld->Sampler()->Parameters());
+        }
+      #endif
       }
-    #endif
-      aTextureIterNew.Next();
     }
     myActiveTextures = theTextures;
   }

src/OpenGl/OpenGl_Context.hxx

@@ -495,6 +495,16 @@ public:
   //! Either GL_CLAMP_TO_EDGE (1.2+) or GL_CLAMP (1.1).
   Standard_Integer TextureWrapClamp() const { return myTexClamp; }
 
+  //! @return true if texture parameters GL_TEXTURE_BASE_LEVEL/GL_TEXTURE_MAX_LEVEL are supported.
+  Standard_Boolean HasTextureBaseLevel() const
+  {
+  #if !defined(GL_ES_VERSION_2_0)
+    return IsGlGreaterEqual (1, 2);
+  #else
+    return IsGlGreaterEqual (3, 0);
+  #endif
+  }
+
   //! @return maximum degree of anisotropy texture filter
   Standard_Integer MaxDegreeOfAnisotropy() const { return myAnisoMax; }
 

src/OpenGl/OpenGl_Sampler.cxx

@@ -263,8 +263,8 @@ void OpenGl_Sampler::applySamplerParams (const Handle(OpenGl_Context)& theCtx,
     setParameter (theCtx, theSampler, theTarget, GL_TEXTURE_MAX_ANISOTROPY_EXT, aDegree);
   }
 
-  if (theCtx->IsGlGreaterEqual(1, 2) &&
-      (theSampler == NULL || !theSampler->isValidSampler()))
+  if (theCtx->HasTextureBaseLevel()
+   && (theSampler == NULL || !theSampler->isValidSampler()))
   {
     setParameter (theCtx, theSampler, theTarget, GL_TEXTURE_BASE_LEVEL, theParams->BaseLevel());
     setParameter (theCtx, theSampler, theTarget, GL_TEXTURE_MAX_LEVEL,  theParams->MaxLevel());

src/OpenGl/OpenGl_TextureSet.hxx

@@ -20,6 +20,7 @@
 class OpenGl_Texture;
 
 //! Class holding array of textures to be mapped as a set.
+//! Textures should be defined in ascending order of texture units within the set.
 class OpenGl_TextureSet : public Standard_Transient
 {
   DEFINE_STANDARD_RTTIEXT(OpenGl_TextureSet, Standard_Transient)
@@ -99,12 +100,18 @@ public:
   //! Return the first texture.
   Handle(OpenGl_Texture)& ChangeFirst() { return myTextures.ChangeFirst().Texture; }
 
+  //! Return the first texture unit.
+  Graphic3d_TextureUnit FirstUnit() const { return myTextures.First().Unit; }
+
   //! Return the last texture.
   const Handle(OpenGl_Texture)& Last() const { return myTextures.Last().Texture; }
 
   //! Return the last texture.
   Handle(OpenGl_Texture)& ChangeLast() { return myTextures.ChangeLast().Texture; }
 
+  //! Return the last texture unit.
+  Graphic3d_TextureUnit LastUnit() const { return myTextures.Last().Unit; }
+
   //! Return the last texture unit.
   Graphic3d_TextureUnit& ChangeLastUnit() { return myTextures.ChangeLast().Unit; }
 

src/OpenGl/OpenGl_TextureSetPairIterator.hxx

@@ -0,0 +1,104 @@
+// Copyright (c) 2020 OPEN CASCADE SAS
+//
+// This file is part of Open CASCADE Technology software library.
+//
+// This library is free software; you can redistribute it and/or modify it under
+// the terms of the GNU Lesser General Public License version 2.1 as published
+// by the Free Software Foundation, with special exception defined in the file
+// OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
+// distribution for complete text of the license and disclaimer of any warranty.
+//
+// Alternatively, this file may be used under the terms of Open CASCADE
+// commercial license or contractual agreement.
+
+#ifndef _OpenGl_TextureSetPairIterator_Header
+#define _OpenGl_TextureSetPairIterator_Header
+
+#include <OpenGl_TextureSet.hxx>
+
+//! Class for iterating pair of texture sets through each defined texture slot.
+//! Note that iterator considers texture slots being in ascending order within OpenGl_TextureSet.
+class OpenGl_TextureSetPairIterator
+{
+public:
+
+  //! Constructor.
+  OpenGl_TextureSetPairIterator (const Handle(OpenGl_TextureSet)& theSet1,
+                                 const Handle(OpenGl_TextureSet)& theSet2)
+  : myIter1 (theSet1),
+    myIter2 (theSet2),
+    myTexture1 (NULL),
+    myTexture2 (NULL),
+    myUnitLower (IntegerLast()),
+    myUnitUpper (IntegerFirst()),
+    myUnitCurrent (0)
+  {
+    if (!theSet1.IsNull()
+     && !theSet1->IsEmpty())
+    {
+      myUnitLower = Min (myUnitLower, theSet1->FirstUnit());
+      myUnitUpper = Max (myUnitUpper, theSet1->LastUnit());
+    }
+    if (!theSet2.IsNull()
+     && !theSet2->IsEmpty())
+    {
+      myUnitLower = Min (myUnitLower, theSet2->FirstUnit());
+      myUnitUpper = Max (myUnitUpper, theSet2->LastUnit());
+    }
+    myUnitCurrent = myUnitLower;
+    myTexture1 = (myIter1.More() && myIter1.Unit() == myUnitCurrent)
+               ? myIter1.ChangeValue().get()
+               : NULL;
+    myTexture2 = (myIter2.More() && myIter2.Unit() == myUnitCurrent)
+               ? myIter2.ChangeValue().get()
+               : NULL;
+  }
+
+  //! Return TRUE if there are more texture units to pass through.
+  bool More() const { return myUnitCurrent <= myUnitUpper; }
+
+  //! Return current texture unit.
+  Graphic3d_TextureUnit Unit() const { return (Graphic3d_TextureUnit )myUnitCurrent; }
+
+  //! Access texture from first texture set.
+  const OpenGl_Texture* Texture1() const { return myTexture1; }
+
+  //! Access texture from second texture set.
+  const OpenGl_Texture* Texture2() const { return myTexture2; }
+
+  //! Move iterator position to the next pair.
+  void Next()
+  {
+    ++myUnitCurrent;
+    myTexture1 = myTexture2 = NULL;
+    for (; myIter1.More(); myIter1.Next())
+    {
+      if (myIter1.Unit() >= myUnitCurrent)
+      {
+        myTexture1 = myIter1.Unit() == myUnitCurrent ? myIter1.ChangeValue().get() : NULL;
+        break;
+      }
+    }
+    for (; myIter2.More(); myIter2.Next())
+    {
+      if (myIter2.Unit() >= myUnitCurrent)
+      {
+        myTexture2 = myIter2.Unit() == myUnitCurrent ? myIter2.ChangeValue().get() : NULL;
+        break;
+      }
+    }
+  }
+
+private:
+
+  OpenGl_TextureSet::Iterator myIter1;
+  OpenGl_TextureSet::Iterator myIter2;
+  OpenGl_Texture*  myTexture1;
+  OpenGl_Texture*  myTexture2;
+  Standard_Integer myUnitLower;
+  Standard_Integer myUnitUpper;
+  Standard_Integer myUnitCurrent;
+
+};
+
+#endif //_OpenGl_TextureSetPairIterator_Header

tests/bugs/vis/bug31315

@@ -0,0 +1,16 @@
+puts "============="
+puts "0031315: Visualization - marker texture is lost after multi-textured object"
+puts "============="
+
+pload MODELING VISUALIZATION
+vclear
+vinit View1
+box b 1 2 3
+vdisplay -dispMode 1 -highMode 1 b
+vtexture b -tex0 3 -tex1 4
+vfit
+vpoint p0 -1 0 0
+vaspects p0 -setMarkerSize 5
+if { [vreadpixel 15 310 -rgb -name] != "BLACK" } { puts "Error: Black color is expected" }
+
+vdump ${imagedir}/${casename}.png