From Melchoir Franz, "ac3d.cpp does currently strip everything but the file name in

"texture" paths. This is to drop absolute paths that some
3d editors export (even AC3D itself!). But this also strips
directories of relative paths, which is wrong and contradicts
the ac3d reference implementation. (The reference implementation
doesn't strip anything, though, and so takes the absolute paths
as they are. Definitely not what we want.)

The attached solution checks absolute paths and only strips
those:

 (1)  A:\\foo\\bar.png   ->   bar.png            (as before)
 (2)  /foo/bar.png       ->   bar.png            (as before)

 (3)  foo/bar.png        ->   foo/bar.png        (new)
 (4)  ../foo/bar.png     ->   ../foo/bar.png     (new)

"

src/osgPlugins/ac/ac3d.cpp

@@ -1121,13 +1121,15 @@ readObject(std::istream& stream, FileData& fileData, const osg::Matrix& parentTr
             // read the texture name
             std::string texname = readString(stream);
 
-            // strip the path to the texture, just look in the directory we read the ac file
+            // strip absolute paths
+            if (texname[0] == '/' || isalpha(texname[0]) && texname[1] == ':') {
                 std::string::size_type p = texname.rfind('\\');
                 if (p != std::string::npos)
                     texname = texname.substr(p+1, std::string::npos);
                 p = texname.rfind('/');
                 if (p != std::string::npos)
                     texname = texname.substr(p+1, std::string::npos);
+            }
         
             textureData  = fileData.toTextureData(texname);
         }