src/jelly/SpringBody.cpp

   1 /*
   2  * Copyright (c) 2007 Walaber
   3  * Modified by Ketmar // Invisible Vector
   4  *
   5  * Permission is hereby granted, free of charge, to any person obtaining a copy
   6  * of this software and associated documentation files (the "Software"), to deal
   7  * in the Software without restriction, including without limitation the rights
   8  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   9  * copies of the Software, and to permit persons to whom the Software is
  10  * furnished to do so, subject to the following conditions:
  11  *
  12  * The above copyright notice and this permission notice shall be included in
  13  * all copies or substantial portions of the Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  18  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  20  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  21  * THE SOFTWARE.
  22  */
  23 #include "SpringBody.h"
  24
  25 #include "World.h"
  26 #include "VectorTools.h"
  27
  28
  29 namespace JellyPhysics {
  30
  31 SpringBody::SpringBody (
  32   World *w, const ClosedShape &shape, float massPerPoint,
  33   float edgeSpringK, float edgeSpringDamp,
  34   const Vector2 &pos, float angleinRadians,
  35   const Vector2 &scale, bool kinematic
  36 ) : Body(w, shape, massPerPoint, pos, angleinRadians, scale, kinematic) {
  37   mShapeMatchingOn = false;
  38   setPositionAngle(pos, angleinRadians, scale);
  39   mEdgeSpringK = edgeSpringK;
  40   mEdgeSpringDamp = edgeSpringDamp;
  41   mShapeSpringK = 0.0f;
  42   mShapeSpringDamp = 0.0f;
  43   // build default springs
  44   _buildDefaultSprings();
  45 }
  46
  47
  48 SpringBody::SpringBody (
  49   World *w, const ClosedShape &shape, float massPerPoint,
  50   float shapeSpringK, float shapeSpringDamp,
  51   float edgeSpringK, float edgeSpringDamp,
  52   const Vector2 &pos, float angleinRadians,
  53   const Vector2 &scale, bool kinematic
  54 ) : Body(w, shape, massPerPoint, pos, angleinRadians, scale, kinematic) {
  55   setPositionAngle(pos, angleinRadians, scale);
  56   mShapeMatchingOn = true;
  57   mShapeSpringK = shapeSpringK;
  58   mShapeSpringDamp = shapeSpringDamp;
  59   mEdgeSpringK = edgeSpringK;
  60   mEdgeSpringDamp = edgeSpringDamp;
  61   // build default springs
  62   _buildDefaultSprings();
  63 }
  64
  65
  66 SpringBody::~SpringBody () {
  67 }
  68
  69
  70 void SpringBody::addInternalSpring (int pointA, int pointB, float springK, float damping) {
  71   float dist = (mPointMasses[pointB].Position-mPointMasses[pointA].Position).length();
  72   InternalSpring s(pointA, pointB, dist, springK, damping);
  73   mSprings.push_back(s);
  74 }
  75
  76
  77 void SpringBody::clearAllSprings () {
  78   mSprings.clear();
  79   _buildDefaultSprings();
  80 }
  81
  82
  83 void SpringBody::_buildDefaultSprings () {
  84   int c = mPointCount, n;
  85   for (int i = 0; i < c; ++i) {
  86     if ((n = i+1) >= c) n = 0;
  87     addInternalSpring(i, n, mEdgeSpringK, mEdgeSpringDamp);
  88   }
  89 }
  90
  91
  92 void SpringBody::setEdgeSpringConstants (float edgeSpringK, float edgeSpringDamp) {
  93   mEdgeSpringK = edgeSpringK;
  94   mEdgeSpringDamp = edgeSpringDamp;
  95   // we know that the first n springs in the list are the edge springs
  96   int c = mPointCount;
  97   for (int i = 0; i < c; ++i) {
  98     mSprings[i].springK = edgeSpringK;
  99     mSprings[i].damping = edgeSpringDamp;
 100   }
 101 }
 102
 103
 104 void SpringBody::setSpringConstants (int springID, float springK, float springDamp) {
 105   // index is for all internal springs, AFTER the default internal springs
 106   int index = mPointCount+springID;
 107   mSprings[index].springK = springK;
 108   mSprings[index].damping = springDamp;
 109 }
 110
 111
 112 float SpringBody::getSpringK (int springID) const {
 113   int index = mPointCount+springID;
 114   return mSprings[index].springK;
 115 }
 116
 117
 118 float SpringBody::getSpringDamping (int springID) const {
 119   int index = mPointCount+springID;
 120   return mSprings[index].damping;
 121 }
 122
 123
 124 void SpringBody::accumulateInternalForces () {
 125   // internal spring forces
 126   Vector2 force;
 127   int i = 0;
 128   for (SpringList::const_iterator it = mSprings.begin(); it != mSprings.end(); ++it, ++i) {
 129     const InternalSpring &s = *it;
 130     PointMass& pmA = mPointMasses[s.pointMassA];
 131     PointMass& pmB = mPointMasses[s.pointMassB];
 132     if (i < mPointCount) {
 133       // spring forces for the edges of the shape can used the cached edge information to reduce calculations
 134       force = calculateSpringForce(-mEdgeInfo[i].dir, mEdgeInfo[i].length, pmA.Velocity, pmB.Velocity, s.springD, s.springK, s.damping);
 135     } else {
 136       // these are other internal springs, they must be fully calculated each frame
 137       force = calculateSpringForce(pmA.Position, pmA.Velocity, pmB.Position, pmB.Velocity, s.springD, s.springK, s.damping);
 138     }
 139     pmA.Force += force;
 140     pmB.Force -= force;
 141   }
 142   // shape matching forces
 143   if (mShapeMatchingOn) {
 144     mBaseShape.transformVertices(mDerivedPos, mDerivedAngle, mScale, mGlobalShape);
 145     for (int i = 0; i < mPointCount; ++i) {
 146       PointMass& pmA = mPointMasses[i];
 147       if (mShapeSpringK > 0) {
 148         if (!mKinematic) {
 149           force = calculateSpringForce(pmA.Position, pmA.Velocity, mGlobalShape[i], pmA.Velocity, 0.0f, mShapeSpringK, mShapeSpringDamp);
 150         } else {
 151           force = calculateSpringForce(pmA.Position, pmA.Velocity, mGlobalShape[i], Vector2::Zero, 0.0f, mShapeSpringK, mShapeSpringDamp);
 152         }
 153         pmA.Force += force;
 154       }
 155     }
 156   }
 157 }
 158
 159 }