105 lines
3.0 KiB
C++
105 lines
3.0 KiB
C++
#include "ExplicitEuler.h"
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#include "CpuSoftClothDemoInternalData.h"
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void ExplicitEuler::computeGravityForces(struct CpuSoftClothDemoInternalData* clothData, char* vertexPositions, int vertexStride, float dt)
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{
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B3_PROFILE("computeForces");
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int numPoints = clothData->m_particleMasses.size();
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b3Vector3 gravityAcceleration = b3MakeVector3(0,-9.8,0);
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//f=m*a
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for (int i=0;i<numPoints;i++)
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{
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{
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float particleMass = clothData->m_particleMasses[i];
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b3Vector3 particleMassVec = b3MakeVector3(particleMass,particleMass,particleMass,0);
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clothData->m_forces[i] = gravityAcceleration*particleMass;
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}
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}
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}
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void ExplicitEuler::computeSpringForces(struct CpuSoftClothDemoInternalData* clothData, char* vertexPositions, int vertexStride, float dt)
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{
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//add spring forces
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for(int i=0;i<clothData->m_springs.size();i++)
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{
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int indexA = clothData->m_springs[i].m_particleIndexA;
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int indexB = clothData->m_springs[i].m_particleIndexB;
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float restLength = clothData->m_springs[i].m_restLength;
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const ClothMaterial& mat = clothData->m_materials[clothData->m_springs[i].m_material];
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const b3Vector3& posA = (const b3Vector3&)vertexPositions[indexA*vertexStride];
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const b3Vector3& posB = (const b3Vector3&)vertexPositions[indexB*vertexStride];
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const b3Vector3& velA = clothData->m_velocities[indexA];
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const b3Vector3& velB = clothData->m_velocities[indexB];
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b3Vector3 deltaP = posA-posB;
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b3Vector3 deltaV = velA-velB;
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float dist = deltaP.length();
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b3Vector3 deltaPNormalized = deltaP/dist;
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float spring = -mat.m_stiffness * (dist-restLength)*100000;
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float damper = mat.m_damping * b3Dot(deltaV,deltaPNormalized)*100;
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b3Vector3 springForce = (spring+damper)*deltaPNormalized;
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float particleMassA = clothData->m_particleMasses[indexA];
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float particleMassB = clothData->m_particleMasses[indexB];
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//if (springForce.length())
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{
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if (particleMassA)
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{
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clothData->m_forces[indexA] += springForce*particleMassA;
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}
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if (particleMassB)
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{
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clothData->m_forces[indexB] -= springForce*particleMassB;
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}
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}
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}
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}
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void ExplicitEuler::integrateExplicitEuler(struct CpuSoftClothDemoInternalData* clothData, char* vertexPositions, int vertexStride,float deltaTime)
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{
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B3_PROFILE("integrateEuler");
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b3Vector3 deltaTimeVec = b3MakeVector3(deltaTime,deltaTime,deltaTime,0);
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int numPoints = clothData->m_particleMasses.size();
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for (int i=0;i<numPoints;i++)
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{
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float mass = clothData->m_particleMasses[i];
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if (mass)
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{
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b3Vector3 dv = (clothData->m_forces[i]/mass)*deltaTimeVec;
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clothData->m_velocities[i]+= dv;
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clothData->m_velocities[i]*=0.999;
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b3Vector3& pos = (b3Vector3&)vertexPositions[i*vertexStride];
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pos += clothData->m_velocities[i]*deltaTimeVec;
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}
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}
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}
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void ExplicitEuler::solveConstraints(struct CpuSoftClothDemoInternalData* data, char* vertexPositions, int vertexStride,float deltaTime)
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{
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computeGravityForces(data,vertexPositions,vertexStride,deltaTime);
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computeSpringForces(data,vertexPositions,vertexStride,deltaTime);
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integrateExplicitEuler(data,vertexPositions,vertexStride,deltaTime);
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} |