Engine directory for ticket #1

Engine/source/forest/forestWindAccumulator.cpp

@@ -0,0 +1,132 @@
+//-----------------------------------------------------------------------------
+// Copyright (c) 2012 GarageGames, LLC
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to
+// deal in the Software without restriction, including without limitation the
+// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+// sell copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+// IN THE SOFTWARE.
+//-----------------------------------------------------------------------------
+
+#include "platform/platform.h"
+#include "forest/forestWindAccumulator.h"
+
+#include "forest/forestWindMgr.h"
+#include "forest/forestItem.h"
+#include "platform/profiler.h"
+
+
+ForestWindAccumulator::ForestWindAccumulator( const TreePlacementInfo &info )
+:  mCurrentStrength( 0.0f )
+{
+   mCurrentDir.set( 0, 0 );   
+   mPosition.set( info.pos );
+   mScale = info.scale;
+
+   mDataBlock = info.dataBlock;
+
+   dMemset( &mParticles[0], 0, sizeof( VerletParticle ) );
+   dMemset( &mParticles[1], 0, sizeof( VerletParticle ) );
+}
+
+ForestWindAccumulator::~ForestWindAccumulator()
+{
+}
+
+void ForestWindAccumulator::presimulate( const VectorF &windVector, U32 ticks )
+{
+   PROFILE_SCOPE( ForestWindAccumulator_Presimulate );
+
+   for ( U32 i = 0; i < ticks; i++ )
+      updateWind( windVector, TickSec );
+}
+
+void ForestWindAccumulator::updateWind( const VectorF &windForce, F32 timeDelta )
+{
+   PROFILE_SCOPE( ForestWindAccumulator_UpdateWind );
+
+   // Update values from datablock... this way we can
+   // change settings live and see instant results.
+   const F32 tightnessCoefficient = mDataBlock->mTightnessCoefficient;
+   const F32 dampingCoefficient = mDataBlock->mDampingCoefficient;
+   const F32 mass = mDataBlock->mMass * mScale;
+   const F32 rigidity = mDataBlock->mRigidity * mScale;
+
+   // This will be the accumulated
+   // target strength for flutter.
+   //F32 targetStrength = windForce.len();
+
+   // This will be the accumulated
+   // target displacement vector.
+   Point2F target( windForce.x, windForce.y );
+
+   // This particle is the spring target.
+   // It has a mass of 0, which we count as
+   // an infinite mass.
+   mParticles[0].position = target;
+
+   Point2F relVel = target * timeDelta;
+
+   Point2F diff( 0, 0 );
+   Point2F springForce( 0, 0 );
+
+   // Spring length is the target
+   // particle's position minus the
+   // current displacement/direction vector.
+   diff = mParticles[0].position - mCurrentDir;
+
+   // F = diff * tightness - v * -damping
+   diff *= tightnessCoefficient;
+   springForce = diff - ( (mParticles[1].position - mParticles[1].lastPosition) * -dampingCoefficient );
+
+   Point2F accel( 0, 0 );
+   accel = springForce * (rigidity * 0.001f) / (mass * 0.001f);
+
+   _updateParticle( &mParticles[1], accel, timeDelta );
+
+   mCurrentDir *= 0.989f;
+   mCurrentDir += mParticles[1].position;
+
+   mCurrentStrength += windForce.len() * timeDelta;
+   mCurrentStrength *= 0.98f;
+}
+
+void ForestWindAccumulator::_updateParticle( VerletParticle *particle, const Point2F &accel, F32 timeDelta )
+{
+   // Verlet integration:
+   // x' = 2x - x* + a * dt^2
+   // x' is the new position.
+   // x is the current position.
+   // x* is the last position.
+   // a is the acceleration for this frame.
+   // dt is the delta time.
+  
+   particle->position = ((particle->position * 2.0f) - particle->lastPosition) + accel * (timeDelta * timeDelta);
+   particle->lastPosition = particle->position;
+}
+
+void ForestWindAccumulator::applyImpulse( const VectorF &impulse )
+{
+   // First build the current force.
+   VectorF force( mCurrentDir.x, mCurrentDir.y, 0 );
+
+   // Add in our mass corrected force.
+   const F32 mass = mDataBlock->mMass * mScale;
+   force += impulse / mass;
+
+   // Set the new direction and force.
+   mCurrentDir.set( force.x, force.y );  
+   mCurrentStrength += impulse.len() * TickSec;
+}