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SIM/SIM_SolverHair.C
/*
* Copyright (c) 2025
* Side Effects Software Inc. All rights reserved.
*
* Redistribution and use of Houdini Development Kit samples in source and
* binary forms, with or without modification, are permitted provided that the
* following conditions are met:
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. The name of Side Effects Software may not be used to endorse or
* promote products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY SIDE EFFECTS SOFTWARE `AS IS' AND ANY EXPRESS
* OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
* NO EVENT SHALL SIDE EFFECTS SOFTWARE BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
* OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*----------------------------------------------------------------------------
*/
#include "SIM_SolverHair.h"
#include <UT/UT_DSOVersion.h>
#include <GU/GU_PrimPoly.h>
#include <PRM/PRM_Include.h>
#include <SIM/SIM_DopDescription.h>
#include <SIM/SIM_GeometryCopy.h>
#include <SIM/SIM_DataFilter.h>
#include <SIM/SIM_Object.h>
#include <SIM/SIM_ObjectArray.h>
#include <SIM/SIM_Engine.h>
#include <SIM/SIM_Force.h>
using namespace HDK_Sample;
void
initializeSIM(void *)
{
IMPLEMENT_DATAFACTORY(SIM_SolverHair);
}
namespace HDK_Sample {
class SIM_HairForceCallback : public SIM_PointForceCallback,
public SIM_EachDataCallback
{
public:
#if defined(HOUDINI_11)
SIM_HairForceCallback(GU_Detail &gdp,
const SIM_Object &object,
const UT_DMatrix4 &xform,
fpreal timestep,
const GB_AttributeRef &massoffset,
const GB_AttributeRef &veloffset);
#else
SIM_HairForceCallback(GU_Detail &gdp,
const SIM_Object &object,
const UT_DMatrix4 &xform,
fpreal timestep,
const GA_RWHandleF &masshandle,
const GA_RWHandleV3 &velhandle);
#endif
~SIM_HairForceCallback() override;
void callbackConst(const SIM_Data *data,
const char *name) override;
void forceCallbackOffset(GA_Offset ptoff,
const UT_Vector3 &force,
const UT_Vector3 &torque) override;
private:
GU_Detail &myGdp;
const SIM_Object &myObject;
const UT_DMatrix4 myTransform;
fpreal myTimestep;
GA_RWHandleF myMassHandle;
GA_RWHandleV3 myVelHandle;
};
} // namespace HDK_Sample
SIM_HairForceCallback::SIM_HairForceCallback(GU_Detail &gdp,
const SIM_Object &object,
const UT_DMatrix4 &xform,
fpreal timestep,
const GA_RWHandleF &masshandle,
const GA_RWHandleV3 &velhandle)
: myGdp(gdp)
, myObject(object)
, myTransform(xform)
, myTimestep(timestep)
, myMassHandle(masshandle)
, myVelHandle(velhandle)
{
}
SIM_HairForceCallback::~SIM_HairForceCallback()
{
}
void
SIM_HairForceCallback::callbackConst(const SIM_Data *data, const char *)
{
const SIM_Force *force = SIM_DATA_CASTCONST(data, SIM_Force);
GU_DetailHandle gdh;
gdh.allocateAndSet(&myGdp, false);
force->getPointForces(*this, myObject, gdh, myTransform, 0, 0, false);
}
void
SIM_HairForceCallback::forceCallbackOffset(GA_Offset ptoff,
const UT_Vector3 &force,
const UT_Vector3 &)
{
float mass = myMassHandle.get(ptoff);
myVelHandle.set(ptoff, myVelHandle.get(ptoff) + (force/mass)*myTimestep);
}
SIM_SolverHair::SIM_SolverHair(const SIM_DataFactory *factory)
: BaseClass(factory),
SIM_OptionsUser(this)
{
}
SIM_SolverHair::~SIM_SolverHair()
{
}
const SIM_DopDescription *
SIM_SolverHair::getSolverHairDopDescription()
{
static PRM_Template theTemplates[] = {
PRM_Template()
};
static SIM_DopDescription theDopDescription(true,
"hdk_hairsolver",
"Hair Solver",
SIM_SOLVER_DATANAME,
classname(),
theTemplates);
return &theDopDescription;
}
void
SIM_SolverHair::solveHair(SIM_GeometryCopy &hairgeo,
const SIM_ObjectArray &srcobjs,
const SIM_Object &object,
const SIM_Time &timestep) const
{
SIM_GeometryAutoWriteLock lock(&hairgeo);
GU_Detail &gdp = lock.getGdp();
UT_DMatrix4 xform;
hairgeo.getTransform(xform);
for (exint geonum = 0; geonum < srcobjs.entries(); geonum++)
{
const SIM_Object *sourceobj = srcobjs(geonum);
const SIM_Geometry *sourcegeo = sourceobj->getGeometry();
if (!sourcegeo || sourcegeo->getGeometry().isNull())
continue;
GU_DetailHandleAutoReadLock sourcegdl(sourcegeo->getGeometry());
const GU_Detail *sourcegdp = sourcegdl.getGdp();
UT_DMatrix4 sourcexform;
SIMgetGeometryTransform(sourcexform, *sourceobj);
#if defined(HOUDINI_11)
const UT_Vector3 zero(0.0, 0.0, 0.0);
const float one = 1.0;
massoffset = gdp.addPointAttrib(
gdp.getStdAttributeName(GEO_ATTRIBUTE_MASS),
sizeof(float), GB_ATTRIB_FLOAT, &one);
veloffset = gdp.addPointAttrib(
gdp.getStdAttributeName(GEO_ATTRIBUTE_VELOCITY),
sizeof(UT_Vector3), GB_ATTRIB_VECTOR, &zero);
#else
GA_RWHandleF masshandle(gdp.addFloatTuple(GA_ATTRIB_POINT,
gdp.getStdAttributeName(GEO_ATTRIBUTE_MASS),
1, GA_Defaults(1.0)));
GA_RWAttributeRef velref = gdp.addFloatTuple(GA_ATTRIB_POINT,
gdp.getStdAttributeName(GEO_ATTRIBUTE_VELOCITY),
3, GA_Defaults(0.0));
velref.setTypeInfo(GA_TYPE_VECTOR); // Transform as vector
GA_RWHandleV3 velhandle(velref);
#endif
// Apply all forces and move the hairs according to those forces.
SIM_HairForceCallback callback(gdp, object, xform, timestep,
masshandle, velhandle);
object.forEachConstSubData(callback,
SIM_DataFilterByType("SIM_Force"),
SIM_FORCES_DATANAME,
SIM_DataFilterNone());
// Integrate our velocities.
{
GA_Offset hairptoff;
GA_FOR_ALL_PTOFF((&gdp), hairptoff)
{
UT_Vector3 dp = velhandle.get(hairptoff);
dp *= timestep;
gdp.setPos3(hairptoff, gdp.getPos3(hairptoff) + dp);
}
}
// Now pull all the points along to make sure the hair length
// remains constant.
GA_Iterator primit(gdp.getPrimitiveRange());
GA_Offset sourceptoff;
GA_FOR_ALL_PTOFF(sourcegdp, sourceptoff)
{
if (primit.atEnd())
break;
GA_Primitive *hairpoly = gdp.getPrimitiveList().get(*primit);
if (hairpoly->getTypeId() == GA_PRIMPOLY &&
hairpoly->getVertexCount() == 10)
{
UT_Vector3 startpos = sourcegdp->getPos3(sourceptoff);
startpos *= sourcexform;
GA_Offset hairpt0off = hairpoly->getPointOffset(0);
GA_Offset hairpt1off = hairpoly->getPointOffset(1);
// Calculate the change in position we need to enforce
// our length constraints. Then calculate the change in
// velocity inherent in this change in position, using
// dp = vt, we get dv = dp/t.
UT_Vector3 dp = startpos - gdp.getPos3(hairpt0off);
UT_Vector3 dv = dp / timestep;
UT_Vector3 vel = velhandle.get(hairpt0off);
vel += dv;
// Apply drag. Just scale down the velocity.
vel *= 0.8;
velhandle.set(hairpt0off, vel);
gdp.setPos3(hairpt0off, gdp.getPos3(hairpt0off) + dp);
GA_Offset hairpt2off;
for (int ptnum = 1; ptnum < 10; ptnum++)
{
if (ptnum < 9)
hairpt2off = hairpoly->getPointOffset(ptnum + 1);
UT_Vector3 midline = gdp.getPos3(hairpt2off) - gdp.getPos3(hairpt0off);
// Calculate the change in position we need to enforce
// our length constraints. Then calculate the change in
// velocity inherent in this change in position, using
// dp = vt, we get dv = dp/t.
dp = midline * (0.1 / midline.length()) +
gdp.getPos3(hairpt0off) - gdp.getPos3(hairpt1off);
dv = dp / timestep;
vel = velhandle.get(hairpt1off);
vel += dv;
// Apply drag. Just scale down the velocity.
vel *= 0.8;
velhandle.set(hairpt1off, vel);
gdp.setPos3(hairpt1off, gdp.getPos3(hairpt1off) + dp);
hairpt0off = hairpt1off;
hairpt1off = hairpt2off;
}
}
++primit;
}
}
}
void
SIM_SolverHair::createHairFromSource(SIM_GeometryCopy &hairgeo,
const SIM_ObjectArray &srcobjs) const
{
SIM_GeometryAutoWriteLock lock(&hairgeo);
GU_Detail &gdp = lock.getGdp();
for (exint geonum = 0; geonum < srcobjs.entries(); geonum++)
{
const SIM_Object *sourceobj = srcobjs(geonum);
const SIM_Geometry *sourcegeo = sourceobj->getGeometry();
if(!sourcegeo || sourcegeo->getGeometry().isNull())
continue;
GU_DetailHandleAutoReadLock sourcegdl(sourcegeo->getGeometry());
const GU_Detail *sourcegdp = sourcegdl.getGdp();
UT_DMatrix4 sourcexform;
SIMgetGeometryTransform(sourcexform, *sourceobj);
GA_Offset sourceptoff;
GA_FOR_ALL_PTOFF(sourcegdp, sourceptoff)
{
UT_Vector4 startpos = sourcegdp->getPos4(sourceptoff);
startpos *= sourcexform;
GU_PrimPoly *newpoly = GU_PrimPoly::build(&gdp, 0, GU_POLY_OPEN, 0);
for (int i = 0; i < 10; i++)
{
GA_Offset newptoff = gdp.appendPointOffset();
gdp.setPos3(newptoff, startpos.x(),
startpos.y() + (fpreal)i * 0.1,
startpos.z());
newpoly->appendVertex(newptoff);
}
}
}
}
SIM_Solver::SIM_Result
SIM_SolverHair::solveSingleObjectSubclass(SIM_Engine & /*engine*/,
SIM_Object &object,
SIM_ObjectArray &,
const SIM_Time &timestep,
bool newobject)
{
SIM_GeometryCopy *hairgeo = 0;
SIM_ObjectArray sourceobjects;
if( newobject )
{
if( !SIM_DATA_GET(object, SIM_GEOMETRY_DATANAME, SIM_GeometryCopy) )
{
hairgeo = SIM_DATA_CREATE(object, SIM_GEOMETRY_DATANAME,
SIM_GeometryCopy, 0);
object.getAffectors(sourceobjects, "SIM_RelationshipSource");
if( hairgeo && sourceobjects.entries() > 0 )
createHairFromSource(*hairgeo, sourceobjects);
}
}
else
{
hairgeo = SIM_DATA_GET(object, SIM_GEOMETRY_DATANAME, SIM_GeometryCopy);
if( hairgeo )
{
object.getAffectors(sourceobjects, "SIM_RelationshipSource");
if( hairgeo && sourceobjects.entries() > 0 )
solveHair(*hairgeo, sourceobjects, object, timestep);
}
}
return hairgeo ? SIM_SOLVER_SUCCESS : SIM_SOLVER_FAIL;
}