src/jelly/PressureBody.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 "PressureBody.h"
  24
  25
  26 namespace JellyPhysics {
  27
  28 PressureBody::~PressureBody () {
  29   delete[] mNormalList;
  30   //delete[] mEdgeLengthList;
  31 }
  32
  33
  34 void PressureBody::accumulateInternalForces () {
  35   SpringBody::accumulateInternalForces();
  36   // internal forces based on pressure equations.  we need 2 loops to do this.  one to find the overall volume of the
  37   // body, and 1 to apply forces.  we will need the normals for the edges in both loops, so we will cache them and remember them.
  38   mVolume = 0.0f;
  39   int c = mPointCount;
  40   for (int i = 0; i < c; ++i) {
  41     int prev = (i > 0 ? i-1 : mPointCount-1);
  42     int next = (i < mPointCount-1 ? i+1 : 0);
  43     PointMass& pmP = mPointMasses[prev];
  44     PointMass& pmI = mPointMasses[i];
  45     PointMass& pmN = mPointMasses[next];
  46     // currently we are talking about the edge from i --> j
  47     // first calculate the volume of the body, and cache normals as we go
  48     Vector2 edge1N = pmI.Position-pmP.Position;
  49     edge1N.makePerpendicular();
  50     Vector2 edge2N = pmN.Position-pmI.Position;
  51     edge2N.makePerpendicular();
  52     Vector2 norm = edge1N+edge2N;
  53     norm.normalise();
  54     float edgeL = mEdgeInfo[i].length; //edge2N.length();
  55     // cache normal and edge length
  56     mNormalList[i] = norm;
  57     //mEdgeLengthList[i] = edgeL;
  58     float xdist = fabsf(pmI.Position.X-pmN.Position.X);
  59     float normX = fabsf(norm.X);
  60     float volumeProduct = xdist*normX*edgeL;
  61     // add to volume
  62     mVolume += 0.5f*volumeProduct;
  63   }
  64   // now loop through, adding forces!
  65   float invVolume = 1.0f/mVolume;
  66   for (int i = 0; i < c; ++i) {
  67     int j = (i < mPointCount-1 ? i+1 : 0);
  68     float pressureV = invVolume*mEdgeInfo[i].length*mGasAmount;
  69     mPointMasses[i].Force += mNormalList[i]*pressureV;
  70     mPointMasses[j].Force += mNormalList[j]*pressureV;
  71   }
  72 }
  73
  74 }