1 #ifndef OPENMW_COMPONENTS_SCENEUTIL_STATESETCONTROLLER_H 2 #define OPENMW_COMPONENTS_SCENEUTIL_STATESETCONTROLLER_H 3 4 #include <osg/NodeCallback> 5 6 namespace SceneUtil 7 { 8 9 /// @brief Implements efficient per-frame updating of StateSets. 10 /// @par With a naive update there would be race conditions when the OSG draw thread of the last frame 11 /// queues up a StateSet that we want to modify for the next frame. To solve this we could set the StateSet to 12 /// DYNAMIC data variance but that would undo all the benefits of the threading model - having the cull and draw 13 /// traversals run in parallel can yield up to 200% framerates. 14 /// @par Race conditions are prevented using a "double buffering" scheme - we have two StateSets that take turns, 15 /// one StateSet we can write to, the second one is currently in use by the draw traversal of the last frame. 16 /// @par Must be set as UpdateCallback or CullCallback on a Node. If set as a CullCallback, the StateSetUpdater operates on an empty StateSet, otherwise it operates on a clone of the node's existing StateSet. 17 /// @note Do not add the same StateSetUpdater to multiple nodes. 18 /// @note Do not add multiple StateSetControllers on the same Node as they will conflict - instead use the CompositeStateSetUpdater. 19 class StateSetUpdater : public osg::NodeCallback 20 { 21 public: 22 StateSetUpdater(); 23 StateSetUpdater(const StateSetUpdater& copy, const osg::CopyOp& copyop); 24 25 META_Object(SceneUtil, StateSetUpdater) 26 27 void operator()(osg::Node* node, osg::NodeVisitor* nv) override; 28 29 /// Apply state - to override in derived classes 30 /// @note Due to the double buffering approach you *have* to apply all state 31 /// even if it has not changed since the last frame. apply(osg::StateSet * stateset,osg::NodeVisitor * nv)32 virtual void apply(osg::StateSet* stateset, osg::NodeVisitor* nv) {} 33 34 /// Set default state - optionally override in derived classes 35 /// @par May be used e.g. to allocate StateAttributes. setDefaults(osg::StateSet * stateset)36 virtual void setDefaults(osg::StateSet* stateset) {} 37 38 protected: 39 /// Reset mStateSets, forcing a setDefaults() on the next frame. Can be used to change the defaults if needed. 40 void reset(); 41 42 private: 43 osg::ref_ptr<osg::StateSet> mStateSets[2]; 44 }; 45 46 /// @brief A variant of the StateSetController that can be made up of multiple controllers all controlling the same target. 47 class CompositeStateSetUpdater : public StateSetUpdater 48 { 49 public: 50 CompositeStateSetUpdater(); 51 CompositeStateSetUpdater(const CompositeStateSetUpdater& copy, const osg::CopyOp& copyop); 52 53 META_Object(SceneUtil, CompositeStateSetUpdater) 54 55 unsigned int getNumControllers(); 56 StateSetUpdater* getController(int i); 57 58 void addController(StateSetUpdater* ctrl); 59 60 void apply(osg::StateSet* stateset, osg::NodeVisitor* nv) override; 61 62 protected: 63 64 void setDefaults(osg::StateSet *stateset) override; 65 66 std::vector<osg::ref_ptr<StateSetUpdater> > mCtrls; 67 }; 68 69 } 70 71 #endif 72