From Jan Peciva,

"please, find attached updates to Inventor plugin:

- improved transparency
- do not treat 32-bit textures as transparent textures unless they really
contain transparent pixels
- error messages forwarded to osg::notify"

src/osgPlugins/Inventor/ConvertFromInventor.cpp

@@ -16,6 +16,7 @@
 #include <osg/BlendFunc>
 #include <osg/Material>
 #include <osg/CullFace>
+#include <osg/Depth>
 #include <osg/LightModel>
 #include <osg/LightSource>
 #include <osg/ShadeModel>
@@ -1697,28 +1698,44 @@ ConvertFromInventor::getStateSet(SoCallbackAction* action)
     // Set transparency
     SbBool hasTextureTransparency = FALSE;
     if (ivTexture) {
-      SbVec2s tmp;
+      SbVec2s size(0, 0);
       int bpp = 0;
+      const unsigned char *data = NULL;
       if (ivTexture->isOfType(SoTexture2::getClassTypeId()))
-        ((SoTexture2*)ivTexture)->image.getValue(tmp, bpp);
+        data = ((SoTexture2*)ivTexture)->image.getValue(size, bpp);
 #ifdef __COIN__
       else
       if (ivTexture->isOfType(SoVRMLImageTexture::getClassTypeId())) {
         const SbImage *img = ((SoVRMLImageTexture*)ivTexture)->getImage();
-        if (img) img->getValue(tmp, bpp);
+        if (img)
+          data = img->getValue(size, bpp);
       }
 #endif
-      hasTextureTransparency = bpp==4 || bpp==2;
+
+      // look whether texture really contains transparency
+      if ((bpp==4 || bpp==2) && data) {
+        data += bpp - 1;
+        for (int y=0; y<size[1]; y++)
+          for (int x=0; x<size[0]; x++, data += bpp)
+            if (*data != 255) {
+              hasTextureTransparency = TRUE;
+              goto finished;
+            }
+      finished:;
+      }
     }
 
     if (transparency > 0 || hasTextureTransparency)
     {
-        osg::ref_ptr<osg::BlendFunc> transparency = new osg::BlendFunc;
-        stateSet->setAttributeAndModes(transparency.get(),
-                                       osg::StateAttribute::ON);
+        // Blending to SRC_APLHA and ONE_MINUS_SRC_ALPHA
+        stateSet->setAttributeAndModes(new osg::BlendFunc);
+
+        // Disable depth writes
+        stateSet->setAttributeAndModes(new osg::Depth(osg::Depth::LEQUAL, 0., 1., false));
 
         // Enable depth sorting for transparent objects
         stateSet->setRenderingHint(osg::StateSet::TRANSPARENT_BIN);
+        stateSet->setNestRenderBins(false);
     }
 
     // Set linewidth

src/osgPlugins/Inventor/ReaderWriterIV.cpp

@@ -7,6 +7,9 @@
 #include <Inventor/SoDB.h>
 #include <Inventor/SoInteraction.h>
 #include <Inventor/nodekits/SoNodeKit.h>
+#include <Inventor/errors/SoDebugError.h>
+#include <Inventor/errors/SoMemoryError.h>
+#include <Inventor/errors/SoReadError.h>
 #include <Inventor/nodes/SoSeparator.h>
 #include <Inventor/actions/SoWriteAction.h>
 #include <Inventor/actions/SoCallbackAction.h>
@@ -21,6 +24,7 @@
 // forward declarations of static functions
 static void addSearchPaths(const osgDB::FilePathList *searchPaths);
 static void removeSearchPaths(const osgDB::FilePathList *searchPaths);
+static void errorCallback(const SoError *error, void * data);
 
 
 // Register with Registry to instantiate the inventor reader.
@@ -52,16 +56,51 @@ void ReaderWriterIV::initInventor() const
     SoNodeKit::init();
     SoInteraction::init();
 
+    // Redirect error messages to OSG notify
+    SoError::setHandlerCallback(errorCallback, NULL);
+    SoDebugError::setHandlerCallback(errorCallback, NULL);
+    SoMemoryError::setHandlerCallback(errorCallback, NULL);
+    SoReadError::setHandlerCallback(errorCallback, NULL);
+
 #ifdef __COIN__
     // Disable delayed loading of VRML textures
     SoVRMLImageTexture::setDelayFetchURL(FALSE);
-    
+
     // initialize convertor
     ConvertFromInventor::init();
 #endif
 }
 
 
+static void errorCallback(const SoError *error, void *data)
+{
+    // note: Coin and SGI Inventor puts "Inventor read error..." or "Coin warning..."
+    // introduction string to the error message, so we do not prepend the error message
+    // by anything.
+
+    if (error->isOfType(SoDebugError::getClassTypeId()))
+    {
+        switch (((SoDebugError*)error)->getSeverity())
+        {
+            case SoDebugError::INFO:
+                OSG_INFO << error->getDebugString().getString() << std::endl;
+                break;
+            case SoDebugError::WARNING:
+                OSG_WARN << error->getDebugString().getString() << std::endl;
+                break;
+            case SoDebugError::ERROR:
+            default:
+                OSG_WARN << error->getDebugString().getString() << std::endl;
+                break;
+        }
+    }
+    else
+    {
+        OSG_WARN << error->getDebugString().getString() << std::endl;
+    }
+}
+
+
 /**
  * Read from SoInput and convert to OSG.
  * This is a method used by readNode(string,options) and readNode(istream,options).