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add Thomas Jacobsen / position based dynamics cloth constraint solver

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This commit is contained in:
erwincoumans
2013-09-06 19:50:58 -07:00
parent 8faac34801
commit 40acf922e3
5 changed files with 94 additions and 18 deletions
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26
Demos3/CpuDemos/deformable/CpuSoftBodyDemo.cpp
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@@ -15,6 +15,7 @@
#include "CpuSoftClothDemoInternalData.h"
#include "ExplicitEuler.h"
#include "PositionBasedDynamics.h"
static b3KeyboardCallback oldCallback = 0;
extern bool gReset;
@@ -22,8 +23,9 @@ extern bool gReset;
float clothWidth = 4;
float clothHeight= 4;
int width = 64;
int height = 64;
int width = 32;//64;
int height = 32;//64;
int numPoints = width*height;
float clothMass = 100.f;
@@ -114,7 +116,7 @@ struct GraphicsVertex
void CpuSoftClothDemo::renderScene()
{
//wireframe
bool wireframe=true;
bool wireframe=false;
if (wireframe)
{
m_instancingRenderer->init();
@@ -157,8 +159,18 @@ void CpuSoftClothDemo::clientMoveAndDisplay()
//write positions
int vertexStride =sizeof(GraphicsVertex);//9 * sizeof(float);
ExplicitEuler::solveConstraints(m_clothData, (char*)m_data->m_clothVertices, vertexStride, deltaTime);
int method = 1;
switch (method)
{
case 0:
ExplicitEuler::solveConstraints(m_clothData, (char*)m_data->m_clothVertices, vertexStride, deltaTime);
break;
case 1:
PositionBasedDynamics::solveConstraints(m_clothData, (char*)m_data->m_clothVertices, vertexStride, deltaTime);
break;
default:
b3Error("unknown method for CpuSoftClothDemo::solveConstraints");
};
//read positions
@@ -260,8 +272,8 @@ void CpuSoftClothDemo::setupScene(const ConstructionInfo& ci)
float posX = (x/((float)(width-1)))*(clothWidth);
float posZ = ((y-height/2.f)/((float)(height-1)))*(clothHeight);
cpu_buffer[y*width+x].pos[0] = posX;
cpu_buffer[y*width+x].pos[1] = coord;
cpu_buffer[y*width+x].pos[0] = 0;
cpu_buffer[y*width+x].pos[1] = -posX;
cpu_buffer[y*width+x].pos[2] = posZ;
cpu_buffer[y*width+x].pos[3] = 0.f;

13
Demos3/CpuDemos/deformable/ExplicitEuler.cpp
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@@ -6,7 +6,7 @@
void ExplicitEuler::computeForces(struct CpuSoftClothDemoInternalData* clothData, char* vertexPositions, int vertexStride, float dt)
void ExplicitEuler::computeGravityForces(struct CpuSoftClothDemoInternalData* clothData, char* vertexPositions, int vertexStride, float dt)
{
B3_PROFILE("computeForces");
@@ -24,10 +24,10 @@ void ExplicitEuler::computeForces(struct CpuSoftClothDemoInternalData* clothData
}
}
}
void ExplicitEuler::computeSpringForces(struct CpuSoftClothDemoInternalData* clothData, char* vertexPositions, int vertexStride, float dt)
{
//add spring forces
for(int i=0;i<clothData->m_springs.size();i++)
@@ -68,9 +68,7 @@ void ExplicitEuler::computeForces(struct CpuSoftClothDemoInternalData* clothData
}
}
}
}
void ExplicitEuler::integrateExplicitEuler(struct CpuSoftClothDemoInternalData* clothData, char* vertexPositions, int vertexStride,float deltaTime)
{
B3_PROFILE("integrateEuler");
@@ -100,7 +98,8 @@ void ExplicitEuler::integrateExplicitEuler(struct CpuSoftClothDemoInternalData*
void ExplicitEuler::solveConstraints(struct CpuSoftClothDemoInternalData* data, char* vertexPositions, int vertexStride,float deltaTime)
{
computeForces(data,vertexPositions,vertexStride,deltaTime);
computeGravityForces(data,vertexPositions,vertexStride,deltaTime);
computeSpringForces(data,vertexPositions,vertexStride,deltaTime);
integrateExplicitEuler(data,vertexPositions,vertexStride,deltaTime);
}

7
Demos3/CpuDemos/deformable/ExplicitEuler.h
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@@ -4,11 +4,12 @@
struct ExplicitEuler
{
static void computeForces(struct CpuSoftClothDemoInternalData* data, char* vtx, int vertexStride, float dt);
static void computeGravityForces(struct CpuSoftClothDemoInternalData* clothData, char* vtx, int vertexStride, float dt);
static void computeSpringForces(struct CpuSoftClothDemoInternalData* clothData, char* vertexPositions, int vertexStride, float dt);
static void integrateExplicitEuler(struct CpuSoftClothDemoInternalData* data, char* vtx, int vertexStride,float dt);
static void integrateExplicitEuler(struct CpuSoftClothDemoInternalData* clothData, char* vtx, int vertexStride,float dt);
static void solveConstraints(struct CpuSoftClothDemoInternalData* data, char* vtx, int vertexStride,float dt);
static void solveConstraints(struct CpuSoftClothDemoInternalData* clothData, char* vtx, int vertexStride,float dt);
};

54
Demos3/CpuDemos/deformable/PositionBasedDynamics.cpp Normal file
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@@ -0,0 +1,54 @@
#include "PositionBasedDynamics.h"
#include "CpuSoftClothDemoInternalData.h"
#include "ExplicitEuler.h"
void PositionBasedDynamics::solveLinks(struct CpuSoftClothDemoInternalData* clothData, char* vertexPositions, int vertexStride,float dt)
{
float kst = 1.f;
float kLST = 1.f;
for(int i=0; i<clothData->m_springs.size();i++)
{
ClothSpring& link=clothData->m_springs[i];
//if(l.m_c0>0)
{
float invMassA = clothData->m_particleMasses[link.m_particleIndexA]? 1.f/clothData->m_particleMasses[link.m_particleIndexA] : 0.f;
float invMassB = clothData->m_particleMasses[link.m_particleIndexB]? 1.f/clothData->m_particleMasses[link.m_particleIndexB] : 0.f;
float m_c0 = (invMassA+invMassB)*kLST;
float m_c1 = link.m_restLength*link.m_restLength;
b3Vector3& posA = (b3Vector3&)vertexPositions[link.m_particleIndexA*vertexStride];
b3Vector3& posB = (b3Vector3&)vertexPositions[link.m_particleIndexB*vertexStride];
const b3Vector3 del=posB-posA;
const float len=del.length2();
if (m_c1+len > B3_EPSILON)
{
const float k=((m_c1-len)/(m_c0*(m_c1+len)))*kst;
posA-=del*(k*invMassA);
posB+=del*(k*invMassB);
}
}
}
}
void PositionBasedDynamics::solveConstraints(struct CpuSoftClothDemoInternalData* clothData, char* vtx, int vertexStride,float dt)
{
B3_PROFILE("computeGravityForces");
ExplicitEuler::computeGravityForces(clothData,vtx,vertexStride,dt);
ExplicitEuler::integrateExplicitEuler(clothData,vtx,vertexStride,dt);
int numIter=10;
for (int i=0;i<numIter;i++)
{
solveLinks(clothData,vtx,vertexStride,dt);
}
};

10
Demos3/CpuDemos/deformable/PositionBasedDynamics.h Normal file
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@@ -0,0 +1,10 @@
#ifndef POSITION_BASED_DYNAMICS_H
#define POSITION_BASED_DYNAMICS_H
struct PositionBasedDynamics
{
static void solveLinks(struct CpuSoftClothDemoInternalData* clothData, char* vtx, int vertexStride,float dt);
static void solveConstraints(struct CpuSoftClothDemoInternalData* data, char* vtx, int vertexStride,float dt);
};
#endif //POSITION_BASED_DYNAMICS_H