Allow loading arbitrary NIF files

components/nif/niffile.cpp

@@ -1,9 +1,12 @@
 #include "niffile.hpp"
 #include "effect.hpp"
 
+#include <array>
 #include <map>
 #include <sstream>
 
+#include <components/settings/settings.hpp>
+
 namespace Nif
 {
 
@@ -137,15 +140,46 @@ void NIFFile::parse(Files::IStreamPtr stream)
 
     // Check the header string
     std::string head = nif.getVersionString();
-    if(head.compare(0, 22, "NetImmerse File Format") != 0)
+    static const std::array<std::string, 2> verStrings =
+    {
+        "NetImmerse File Format",
+        "Gamebryo File Format"
+    };
+    bool supported = false;
+    for (const std::string& verString : verStrings)
+    {
+        supported = (head.compare(0, verString.size(), verString) == 0);
+        if (supported)
+            break;
+    }
+    if (!supported)
         fail("Invalid NIF header: " + head);
 
+    supported = false;
+
     // Get BCD version
     ver = nif.getUInt();
     // 4.0.0.0 is an older, practically identical version of the format.
     // It's not used by Morrowind assets but Morrowind supports it.
-    if(ver != NIFStream::generateVersion(4,0,0,0) && ver != VER_MW)
+    static const std::array<uint32_t, 2> supportedVers =
+    {
+        NIFStream::generateVersion(4,0,0,0),
+        VER_MW
+    };
+    for (uint32_t supportedVer : supportedVers)
+    {
+        supported = (ver == supportedVer);
+        if (supported)
+            break;
+    }
+    if (!supported)
+    {
+        static const bool ignoreUnsupported = Settings::Manager::getBool("load unsupported nif files", "Models");
+        if (ignoreUnsupported)
+            warn("Unsupported NIF version: " + printVersion(ver) + ". Proceed with caution!");
+        else
             fail("Unsupported NIF version: " + printVersion(ver));
+    }
 
     // NIF data endianness
     if (ver >= NIFStream::generateVersion(20,0,0,4))
@@ -245,6 +279,9 @@ void NIFFile::parse(Files::IStreamPtr stream)
         else
             fail("Unknown record type " + rec);
 
+        if (!supported)
+            Log(Debug::Verbose) << "NIF Debug: Reading record of type " << rec << ", index " << i << " (" << filename << ")";
+
         assert(r != nullptr);
         assert(r->recType != RC_MISSING);
         r->recName = rec;

docs/source/reference/modding/settings/index.rst

@@ -58,3 +58,4 @@ The ranges included with each setting are the physically possible ranges, not re
 	windows
 	navigator
 	physics
+	models

docs/source/reference/modding/settings/models.rst

@@ -0,0 +1,27 @@
+Models Settings
+###############
+
+load unsupported nif files
+--------------------------
+
+:Type:		boolean
+:Range:		True/False
+:Default:	False
+
+At the moment OpenMW's NIF loader is only tailored to load models
+that can also load in Morrowind.
+
+However, you can enable its limited and experimental support for updates in
+the definitions of record types from later NIF revisions by toggling on
+this setting.
+
+You must keep in mind that loading unsupported NIF files may fail,
+and the degree of this failure may vary. In milder cases, OpenMW will reject
+the file anyway because it lacks a definition for a certain record type
+that the file may use. In more severe cases OpenMW's
+incomplete understanding of a record type can lead to memory corruption,
+crashes or even freezes. Don't enable this if you're not sure that
+you know what you're doing.
+
+To help debug possible issues OpenMW will log its progress in loading
+every file that uses an unsupported NIF version.

files/settings-default.cfg

@@ -945,3 +945,8 @@ lineofsight keep inactive cache = 0
 
 # Defer bounding boxes update until collision detection.
 defer aabb update = true
+
+[Models]
+# Attempt to load any valid NIF file regardless of its version and track the progress.
+# Loading arbitrary meshes is not advised and may cause instability.
+load unsupported nif files = false