From ad46ff7a98fb2bd201e9309b76400f3a7fe61d4d Mon Sep 17 00:00:00 2001
From: scrawl <scrawl@baseoftrash.de>
Date: Mon, 15 Jun 2015 02:06:04 +0200
Subject: [PATCH] Remove redundant Transform nodes for
 TriShapes/ParticleSystems with an identity transform

---
 components/nif/niftypes.hpp     | 15 +++++++++++++++
 components/nifosg/nifloader.cpp | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/components/nif/niftypes.hpp b/components/nif/niftypes.hpp
index d951801452..5827448fdf 100644
--- a/components/nif/niftypes.hpp
+++ b/components/nif/niftypes.hpp
@@ -42,6 +42,15 @@ struct Matrix3
             for (int j=0;j<3;++j)
                 mValues[i][j] = (i==j) ? 1.f : 0.f;
     }
+
+    bool isIdentity() const
+    {
+        for (int i=0;i<3;++i)
+            for (int j=0;j<3;++j)
+                if ((i==j) != (mValues[i][j] == 1))
+                    return false;
+        return true;
+    }
 };
 
 struct Transformation
@@ -62,6 +71,12 @@ struct Transformation
         return transform;
     }
 
+    bool isIdentity() const
+    {
+        return pos == osg::Vec3f(0,0,0)
+                && rotation.isIdentity() && scale == 1.f;
+    }
+
     static const Transformation& getIdentity()
     {
         static const Transformation identity = {
diff --git a/components/nifosg/nifloader.cpp b/components/nifosg/nifloader.cpp
index 7aec3385e3..7139bbcef8 100644
--- a/components/nifosg/nifloader.cpp
+++ b/components/nifosg/nifloader.cpp
@@ -376,6 +376,32 @@ namespace NifOsg
             toSetup->setFunction(boost::shared_ptr<ControllerFunction>(new ControllerFunction(ctrl)));
         }
 
+        void optimize (const Nif::Node* nifNode, osg::Group* node, bool skipMeshes)
+        {
+            // For nodes with an identity transform, remove the redundant Transform node
+            if (node->getDataVariance() == osg::Object::STATIC
+                    // For TriShapes, we can only collapse the node, but not completely remove it,
+                    // if the link to animated collision shapes is supposed to stay intact.
+                    && (nifNode->recType != Nif::RC_NiTriShape || !skipMeshes))
+            {
+                if (node->getNumParents() && nifNode->trafo.isIdentity())
+                {
+                    osg::Group* parent = node->getParent(0);
+                    osg::Node* child = node->getChild(0);
+                    child->setUpdateCallback(node->getUpdateCallback());
+                    child->setStateSet(node->getStateSet());
+                    child->setName(node->getName());
+                    // make sure to copy the UserDataContainer with the record index, so that connections to an animated collision shape don't break
+                    child->setUserDataContainer(node->getUserDataContainer());
+                    parent->addChild(child);
+                    node->removeChild(child);
+                    parent->removeChild(node);
+                }
+            }
+            // For NiTriShapes *with* a valid transform, perhaps we could apply the transform to the vertices.
+            // Need to make sure that won't break transparency sorting. Check what the original engine is doing?
+        }
+
         osg::ref_ptr<osg::Node> handleNode(const Nif::Node* nifNode, osg::Group* parentNode, Resource::TextureManager* textureManager,
                                 std::map<int, int> boundTextures, int animflags, int particleflags, bool skipMeshes, TextKeyMap* textKeys, osg::Node* rootNode=NULL)
         {
@@ -490,9 +516,15 @@ namespace NifOsg
             if (composite->getNumControllers() > 0)
                 transformNode->addUpdateCallback(composite);
 
+
+            // Note: NiTriShapes are not allowed to have KeyframeControllers (the vanilla engine just crashes when there is one).
+            // We can take advantage of this constraint for optimizations later.
             if (!nifNode->controller.empty())
                 handleNodeControllers(nifNode, transformNode, animflags);
 
+            // Optimization pass
+            optimize(nifNode, transformNode, skipMeshes);
+
             const Nif::NiNode *ninode = dynamic_cast<const Nif::NiNode*>(nifNode);
             if(ninode)
             {