ENH: Improve scene exporters and STL, OBJ, and PLY file IO

- Allow reading/writing custom comments in STL, PLY, and OBJ files. This allows storing metadata, such as coordinate system, unit, or color in the files.
- Allow reading/writing binary comments (that can contain 0 character) for STL files. This allows reading/writing color information in Mimics-style (Mimics software writes RGBA color as 4 bytes in STL file binary header).
- Allow specifying renderer for exporting: Some exporters rejected to export a scene when more renderers were associated with a render window. This was an issue because it prevented scene export when additional renderers were used for displaying various annotations on the render window. Instead of hardcoding using the first renderer, added a ActiveRenderer member, which defines which renderer content should be exported. If not set then the first renderer is used, so the behavior is backward-compatible.
- Fixed writing of of .mtl file path in .obj file (full path of .mtl file was written into the .obj file).

Author: lassoan

IO/Export/Testing/Cxx/UnitTestRIB.cxx

@@ -343,14 +343,13 @@ int TestRIBExporter()
 
   vtkSmartPointer<vtkRenderer> ren2 =
     vtkSmartPointer<vtkRenderer>::New ();
-  renWin->AddRenderer(ren2);
   exporter->SetFilePrefix("dummy");
+  exporter->SetActiveRenderer(ren2);
   exporter->Update();
-  status += errorObserver->CheckErrorMessage("RIB files only support one renderer per window");
+  status += errorObserver->CheckErrorMessage("ActiveRenderer must be a renderer owned by the RenderWindow");
 
-  renWin->RemoveRenderer(ren2);
-  ren1->RemoveActor(sphere);
-  ren1->RemoveActor(strip);
+  renWin->AddRenderer(ren2);
+  exporter->SetActiveRenderer(ren2);
   exporter->Update();
   status += errorObserver->CheckErrorMessage("No actors found for writing .RIB file");
 

IO/Export/module.cmake

@@ -38,4 +38,5 @@ vtk_module(vtkIOExport
     vtkIOImage
     vtkImagingCore
     vtklibharu
+    vtksys
   )

IO/Export/vtkExporter.cxx

@@ -15,15 +15,18 @@
 #include "vtkExporter.h"
 
 #include "vtkRenderWindow.h"
+#include "vtkRenderer.h"
 
 
 vtkCxxSetObjectMacro(vtkExporter,RenderWindow,vtkRenderWindow);
+vtkCxxSetObjectMacro(vtkExporter,ActiveRenderer,vtkRenderer);
 
 
 // Construct with no start and end write methods or arguments.
 vtkExporter::vtkExporter()
 {
   this->RenderWindow = nullptr;
+  this->ActiveRenderer = nullptr;
   this->StartWrite = nullptr;
   this->StartWriteArgDelete = nullptr;
   this->StartWriteArg = nullptr;
@@ -35,6 +38,7 @@ vtkExporter::vtkExporter()
 vtkExporter::~vtkExporter()
 {
   this->SetRenderWindow(nullptr);
+  this->SetActiveRenderer(nullptr);
 
   if ((this->StartWriteArg)&&(this->StartWriteArgDelete))
   {
@@ -57,6 +61,12 @@ void vtkExporter::Write()
     vtkErrorMacro(<< "No render window provided!");
     return;
   }
+  if ( this->ActiveRenderer != nullptr
+    && !this->RenderWindow->HasRenderer(this->ActiveRenderer) )
+  {
+    vtkErrorMacro(<< "ActiveRenderer must be a renderer owned by the RenderWindow");
+    return;
+  }
 
   if ( this->StartWrite )
   {
@@ -144,6 +154,16 @@ void vtkExporter::PrintSelf(ostream& os, vtkIndent indent)
     os << indent << "Render Window: (none)\n";
   }
 
+  if ( this->ActiveRenderer )
+  {
+    os << indent << "Active Renderer: (" <<
+      static_cast<void *>(this->ActiveRenderer) << ")\n";
+  }
+  else
+  {
+    os << indent << "Active Renderer: (none)\n";
+  }
+
   if ( this->StartWrite )
   {
     os << indent << "Start Write: (" <<

IO/Export/vtkExporter.h

@@ -42,6 +42,7 @@
 #include "vtkIOExportModule.h" // For export macro
 #include "vtkObject.h"
 class vtkRenderWindow;
+class vtkRenderer;
 
 class VTKIOEXPORT_EXPORT vtkExporter : public vtkObject
 {
@@ -68,6 +69,21 @@ class VTKIOEXPORT_EXPORT vtkExporter : public vtkObject
   vtkGetObjectMacro(RenderWindow,vtkRenderWindow);
   //@}
 
+  //@{
+  /**
+   * Set/Get the renderer that contains actors to be written.
+   * If it is set to nullptr (by default), then in most subclasses
+   * the behavior is to only export actors of the first renderer.
+   * In some subclasses, if ActiveRenderer is nullptr then
+   * actors of all renderers will be exported.
+   * The renderer must be in the renderer collection of the specified
+   * RenderWindow.
+   * \sa SetRenderWindow()
+   */
+  virtual void SetActiveRenderer(vtkRenderer*);
+  vtkGetObjectMacro(ActiveRenderer,vtkRenderer);
+  //@}
+
   //@{
   /**
    * These methods are provided for backward compatibility. Will disappear
@@ -109,6 +125,7 @@ class VTKIOEXPORT_EXPORT vtkExporter : public vtkObject
   ~vtkExporter() override;
 
   vtkRenderWindow *RenderWindow;
+  vtkRenderer *ActiveRenderer;
   virtual void WriteData() = 0;
 
   void (*StartWrite)(void *);

IO/Export/vtkIVExporter.cxx

@@ -28,8 +28,8 @@
 #include "vtkPolyData.h"
 #include "vtkPolyDataMapper.h"
 #include "vtkProperty.h"
-#include "vtkRenderWindow.h"
 #include "vtkRendererCollection.h"
+#include "vtkRenderWindow.h"
 #include "vtkTexture.h"
 #include "vtkTransform.h"
 #include "vtkUnsignedCharArray.h"
@@ -57,7 +57,6 @@ static int indent_now = 0;
 
 void vtkIVExporter::WriteData()
 {
-  vtkRenderer *ren;
   FILE *fp;
   vtkActorCollection *ac;
   vtkActor *anActor, *aPart;
@@ -79,16 +78,13 @@ void vtkIVExporter::WriteData()
     return;
   }
 
-  // first make sure there is only one renderer in this rendering window
-  if (this->RenderWindow->GetRenderers()->GetNumberOfItems() > 1)
+  // get the renderer
+  vtkRenderer *ren = this->ActiveRenderer;
+  if (!ren)
   {
-    vtkErrorMacro(<< "OpenInventor files only support one renderer per window.");
-    return;
+    ren = this->RenderWindow->GetRenderers()->GetFirstRenderer();
   }
 
-  // get the renderer
-  ren = this->RenderWindow->GetRenderers()->GetFirstRenderer();
-
   // make sure it has at least one actor
   if (ren->GetActors()->GetNumberOfItems() < 1)
   {

IO/Export/vtkOBJExporter.cxx

@@ -27,15 +27,21 @@
 #include "vtkPointData.h"
 #include "vtkPolyData.h"
 #include "vtkProperty.h"
-#include "vtkRenderWindow.h"
 #include "vtkRendererCollection.h"
+#include "vtkRenderWindow.h"
 #include "vtkTransform.h"
+#include "vtksys/SystemTools.hxx"
 
 vtkStandardNewMacro(vtkOBJExporter);
 
 vtkOBJExporter::vtkOBJExporter()
 {
   this->FilePrefix = nullptr;
+  this->OBJFileComment = nullptr;
+  this->MTLFileComment = nullptr;
+
+  this->SetOBJFileComment("wavefront obj file written by the visualization toolkit");
+  this->SetMTLFileComment("wavefront mtl file written by the visualization toolkit");
 }
 
 vtkOBJExporter::~vtkOBJExporter()
@@ -45,31 +51,19 @@ vtkOBJExporter::~vtkOBJExporter()
 
 void vtkOBJExporter::WriteData()
 {
-  vtkRenderer *ren;
-  FILE *fpObj, *fpMtl;
-  vtkActorCollection *ac;
-  vtkActor *anActor, *aPart;
-  char nameObj[2048];
-  char nameMtl[2048];
-  int idStart = 1;
-
   // make sure the user specified a filename
   if ( this->FilePrefix == nullptr)
   {
     vtkErrorMacro(<< "Please specify file prefix to use");
     return;
   }
 
-  // first make sure there is only one renderer in this rendering window
-  if (this->RenderWindow->GetRenderers()->GetNumberOfItems() > 1)
+  vtkRenderer *ren = this->ActiveRenderer;
+  if (!ren)
   {
-    vtkErrorMacro(<< "obj files only support on renderer per window.");
-    return;
+    ren = this->RenderWindow->GetRenderers()->GetFirstRenderer();
   }
 
-  // get the renderer
-  ren = this->RenderWindow->GetRenderers()->GetFirstRenderer();
-
   // make sure it has at least one actor
   if (ren->GetActors()->GetNumberOfItems() < 1)
   {
@@ -78,15 +72,15 @@ void vtkOBJExporter::WriteData()
   }
 
   // try opening the files
-  snprintf(nameObj,sizeof(nameObj),"%s.obj",this->FilePrefix);
-  snprintf(nameMtl,sizeof(nameMtl),"%s.mtl",this->FilePrefix);
-  fpObj = fopen(nameObj,"w");
+  std::string objFilePath = std::string(this->FilePrefix) + ".obj";
+  FILE *fpObj = fopen(objFilePath.c_str(), "w");
   if (!fpObj)
   {
     vtkErrorMacro(<< "unable to open .obj files ");
     return;
   }
-  fpMtl = fopen(nameMtl,"w");
+  std::string mtlFilePath = std::string(this->FilePrefix) + ".mtl";
+  FILE *fpMtl = fopen(mtlFilePath.c_str(), "w");
   if (!fpMtl)
   {
     fclose(fpObj);
@@ -98,20 +92,30 @@ void vtkOBJExporter::WriteData()
   //  Write header
   //
   vtkDebugMacro("Writing wavefront files");
-  fprintf(fpObj,
-          "# wavefront obj file written by the visualization toolkit\n\n");
-  fprintf(fpObj, "mtllib %s\n\n", nameMtl);
-  fprintf(fpMtl,
-          "# wavefront mtl file written by the visualization toolkit\n\n");
-
-  ac = ren->GetActors();
-  vtkAssemblyPath *apath;
-  vtkCollectionSimpleIterator ait;
-  for (ac->InitTraversal(ait); (anActor = ac->GetNextActor(ait)); )
+  if (this->GetOBJFileComment())
+  {
+    fprintf(fpObj, "# %s\n\n", this->GetOBJFileComment());
+  }
+
+  std::string mtlFileName = vtksys::SystemTools::GetFilenameName(mtlFilePath);
+  fprintf(fpObj, "mtllib %s\n\n", mtlFileName.c_str());
+
+  if (this->GetMTLFileComment())
   {
-    for (anActor->InitPathTraversal(); (apath=anActor->GetNextPath()); )
+    fprintf(fpMtl, "# %s\n\n", this->GetMTLFileComment());
+  }
+
+
+  vtkActorCollection *allActors = ren->GetActors();
+  vtkCollectionSimpleIterator actorsIt;
+  vtkActor *anActor;
+  int idStart = 1;
+  for (allActors->InitTraversal(actorsIt); (anActor = allActors->GetNextActor(actorsIt)); )
+  {
+    vtkAssemblyPath *aPath;
+    for (anActor->InitPathTraversal(); (aPath = anActor->GetNextPath()); )
     {
-      aPart=static_cast<vtkActor *>(apath->GetLastNode()->GetViewProp());
+      vtkActor *aPart = vtkActor::SafeDownCast(aPath->GetLastNode()->GetViewProp());
       this->WriteAnActor(aPart, fpObj, fpMtl, idStart);
     }
   }
@@ -383,13 +387,7 @@ void vtkOBJExporter::PrintSelf(ostream& os, vtkIndent indent)
 {
   this->Superclass::PrintSelf(os,indent);
 
-  if (this->FilePrefix)
-  {
-    os << indent << "FilePrefix: " << this->FilePrefix << "\n";
-  }
-  else
-  {
-    os << indent << "FilePrefix: (null)\n";
-  }
+  os << indent << "FilePrefix: " << (this->FilePrefix ? this->FilePrefix : "(null)") << "\n";
+  os << indent << "OBJFileComment: " << (this->OBJFileComment ? this->OBJFileComment : "(null)") << "\n";
+  os << indent << "MTLFileComment: " << (this->MTLFileComment ? this->MTLFileComment : "(null)") << "\n";
 }
-

IO/Export/vtkOBJExporter.h

@@ -49,13 +49,31 @@ class VTKIOEXPORT_EXPORT vtkOBJExporter : public vtkExporter
   vtkGetStringMacro(FilePrefix);
   //@}
 
+  //@{
+  /**
+  * Specify comment string that will be written to the obj file header.
+  */
+  vtkSetStringMacro(OBJFileComment);
+  vtkGetStringMacro(OBJFileComment);
+  //@}
+
+  //@{
+  /**
+  * Specify comment string that will be written to the mtl file header.
+  */
+  vtkSetStringMacro(MTLFileComment);
+  vtkGetStringMacro(MTLFileComment);
+  //@}
+
 protected:
   vtkOBJExporter();
   ~vtkOBJExporter() override;
 
   void WriteData() override;
   void WriteAnActor(vtkActor *anActor, FILE *fpObj, FILE *fpMat, int &id);
   char *FilePrefix;
+  char *OBJFileComment;
+  char *MTLFileComment;
 private:
   vtkOBJExporter(const vtkOBJExporter&) = delete;
   void operator=(const vtkOBJExporter&) = delete;

IO/Export/vtkOOGLExporter.cxx

@@ -57,7 +57,6 @@ static int indent_now = 0;
 
 void vtkOOGLExporter::WriteData()
 {
-  vtkRenderer *ren;
   FILE *fp;
   int i, j;
   vtkActorCollection *ac;
@@ -81,16 +80,12 @@ void vtkOOGLExporter::WriteData()
     return;
   }
 
-  // first make sure there is only one renderer in this rendering window
-  if (this->RenderWindow->GetRenderers()->GetNumberOfItems() > 1)
+  vtkRenderer *ren = this->ActiveRenderer;
+  if (!ren)
   {
-    vtkErrorMacro(<< "Support for only one renderer per window.");
-    return;
+    ren = this->RenderWindow->GetRenderers()->GetFirstRenderer();
   }
 
-  // get the renderer
-  ren = this->RenderWindow->GetRenderers()->GetFirstRenderer();
-
   // make sure it has at least one actor
   if (ren->GetActors()->GetNumberOfItems() < 1)
   {

IO/Export/vtkPDFExporter.cxx

@@ -152,6 +152,11 @@ void vtkPDFExporter::RenderContextActors()
     vtkRenderer *ren;
     for (renCol->InitTraversal(renIt); (ren = renCol->GetNextRenderer(renIt));)
     {
+      if (this->ActiveRenderer && ren != this->ActiveRenderer)
+      {
+        // If ActiveRenderer is specified then ignore all other renderers
+        continue;
+      }
       if (ren->GetLayer() == i)
       {
         vtkPropCollection *props = ren->GetViewProps();

IO/Export/vtkPDFExporter.h

@@ -17,6 +17,9 @@
  * @brief Exports vtkContext2D scenes to PDF.
  *
  * This exporter draws context2D scenes into a PDF file.
+ *
+ * If ActiveRenderer is specified then it exports contents of
+ * ActiveRenderer. Otherwise it exports contents of all renderers.
  */
 
 #ifndef vtkPDFExporter_h