From c23609e22b1d931274b93c3ce031c682cf6176ff Mon Sep 17 00:00:00 2001
From: scrawl <scrawl@baseoftrash.de>
Date: Wed, 4 Nov 2015 00:19:15 +0100
Subject: [PATCH] Cache the light list in LightListCallback

When multiple cameras are rendering, the later cameras can reuse the light lists from the first camera.
---
 components/sceneutil/lightmanager.cpp | 37 +++++++++++++++------------
 components/sceneutil/lightmanager.hpp |  4 +++
 2 files changed, 25 insertions(+), 16 deletions(-)

diff --git a/components/sceneutil/lightmanager.cpp b/components/sceneutil/lightmanager.cpp
index 18d7ddd46..1e1d04cf5 100644
--- a/components/sceneutil/lightmanager.cpp
+++ b/components/sceneutil/lightmanager.cpp
@@ -280,37 +280,40 @@ namespace SceneUtil
         // - cull list of lights by the camera frustum
         // - organize lights in a quad tree
 
-        // Don't use Camera::getViewMatrix, that one might be relative to another camera!
-        const osg::RefMatrix* viewMatrix = cv->getCurrentRenderStage()->getInitialViewMatrix();
 
-        const std::vector<LightManager::LightSourceViewBound>& lights = mLightManager->getLightsInViewSpace(cv->getCurrentCamera(), viewMatrix);
-
-        if (lights.size())
+        // update light list if necessary
+        // makes sure we don't update it more than once per frame when rendering with multiple cameras
+        if (mLastFrameNumber != nv->getFrameStamp()->getFrameNumber())
         {
+            mLastFrameNumber = nv->getFrameStamp()->getFrameNumber();
+
+            // Don't use Camera::getViewMatrix, that one might be relative to another camera!
+            const osg::RefMatrix* viewMatrix = cv->getCurrentRenderStage()->getInitialViewMatrix();
+            const std::vector<LightManager::LightSourceViewBound>& lights = mLightManager->getLightsInViewSpace(cv->getCurrentCamera(), viewMatrix);
+
             // we do the intersections in view space
             osg::BoundingSphere nodeBound = node->getBound();
             osg::Matrixf mat = *cv->getModelViewMatrix();
             transformBoundingSphere(mat, nodeBound);
 
-            LightManager::LightList lightList;
+            mLightList.clear();
             for (unsigned int i=0; i<lights.size(); ++i)
             {
                 const LightManager::LightSourceViewBound& l = lights[i];
                 if (l.mViewBound.intersects(nodeBound))
-                    lightList.push_back(&l);
-            }
-
-            if (lightList.empty())
-            {
-                traverse(node, nv);
-                return;
+                    mLightList.push_back(&l);
             }
-
+        }
+        if (mLightList.size())
+        {
             unsigned int maxLights = static_cast<unsigned int> (8 - mLightManager->getStartLight());
 
-            if (lightList.size() > maxLights)
+            osg::StateSet* stateset = NULL;
+
+            if (mLightList.size() > maxLights)
             {
                 // remove lights culled by this camera
+                LightManager::LightList lightList = mLightList;
                 for (LightManager::LightList::iterator it = lightList.begin(); it != lightList.end() && lightList.size() > maxLights; )
                 {
                     osg::CullStack::CullingStack& stack = cv->getModelViewCullingStack();
@@ -334,9 +337,11 @@ namespace SceneUtil
                     while (lightList.size() > maxLights)
                         lightList.pop_back();
                 }
+                stateset = mLightManager->getLightListStateSet(lightList);
             }
+            else
+                stateset = mLightManager->getLightListStateSet(mLightList);
 
-            osg::StateSet* stateset = mLightManager->getLightListStateSet(lightList);
 
             cv->pushStateSet(stateset);
 
diff --git a/components/sceneutil/lightmanager.hpp b/components/sceneutil/lightmanager.hpp
index c2a1779ed..0783e595d 100644
--- a/components/sceneutil/lightmanager.hpp
+++ b/components/sceneutil/lightmanager.hpp
@@ -113,11 +113,13 @@ namespace SceneUtil
         int mStartLight;
     };
 
+    /// @note Not thread safe for CullThreadPerCamera threading mode.
     class LightListCallback : public osg::NodeCallback
     {
     public:
         LightListCallback()
             : mLightManager(NULL)
+            , mLastFrameNumber(0)
         {}
         LightListCallback(const LightListCallback& copy, const osg::CopyOp& copyop = osg::CopyOp::SHALLOW_COPY)
             : osg::Object(copy, copyop), osg::NodeCallback(copy, copyop), mLightManager(copy.mLightManager)
@@ -129,6 +131,8 @@ namespace SceneUtil
 
     private:
         LightManager* mLightManager;
+        unsigned int mLastFrameNumber;
+        LightManager::LightList mLightList;
     };
 
     /// @brief Configures a light's attenuation according to vanilla Morrowind attenuation settings.