SIM_ForceOrbit.h

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/// @file SIM_ForceOrbit.h
/// This example creates a custom force DOP.
///
/// This class will add a new DOP node called Orbit Force.  This node will
/// attach a SIM_ForceOrbit instance on DOP objects.  Solvers will discover
/// this instance when iterating over the applied forces and can call one of
/// getForce*() methods to find out the applied force and torque values.
/// Houdini will also use the createGuideObject() method to display guide
/// geometry.

#ifndef __SIM_ForceOrbit_h__
#define __SIM_ForceOrbit_h__

#include <SIM/SIM_Force.h>
#include <SIM/SIM_OptionsUser.h>

#define SIM_NAME_POINTMASS      "pointmass"
#define SIM_NAME_POINTPOSITION  "pointposition"

namespace HDK_Sample {

/// This is an implementation of the SIM_Force interface. This
/// implementation returns a force value that is proportional to the
/// square of the distance from a point in space (as if there were an
/// infinitely small massive body at that location).
class SIM_ForceOrbit : public SIM_Force,
                       public SIM_OptionsUser
{
public:
    /// Controls the position of the point we are orbiting.
    GETSET_DATA_FUNCS_V3(SIM_NAME_POINTPOSITION, PointPosition);
    /// Controls the mass of the point we are orbiting.
    GETSET_DATA_FUNCS_F(SIM_NAME_POINTMASS, PointMass);

protected:
    /// Declare a protected constructor to ensure the data factory is used to
    /// create new instances of SIM_ForceOrbit.
    explicit             SIM_ForceOrbit(const SIM_DataFactory *factory);
                        ~SIM_ForceOrbit() override;

    /// Override this to return a SIM_GuideShared as the guide geometry looks
    /// the same for all objects.
    SIM_Guide           *createGuideObjectSubclass() const override;

    /// We override this method to create the attractor geometry.
    void                 buildGuideGeometrySubclass(const SIM_RootData &root,
                                                    const SIM_Options &options,
                                                    const GU_DetailHandle &gdh,
                                                    UT_DMatrix4 *xform,
                                                    const SIM_Time &t
                                                    ) const override;

    /// Calculates the force on a point. The force depends only on the
    /// mass of the point.
    void                 getForceSubclass(const SIM_Object &object,
                                        const UT_Vector3 &position,
                                        const UT_Vector3 &velocity,
                                        const UT_Vector3 &angvel,
                                        const fpreal mass,
                                        UT_Vector3 &force,
                                        UT_Vector3 &torque) const override;
    /// Calculates the force on a surface. The force depends only
    /// on the mass, so this function simply calls getForceSubclass(),
    /// ignoring the circle parameters.
    void                 getForceOnCircleSubclass(const SIM_Object &object,
                                        const UT_Vector3 &position,
                                        const UT_Vector3 &normal,
                                        const fpreal radius,
                                        const UT_Vector3 &velocity,
                                        const UT_Vector3 &angvel,
                                        const fpreal mass,
                                        UT_Vector3 &force,
                                        UT_Vector3 &torque) const override;
    /// Calculates the force on a volume. The force depends only
    /// on the mass, so this function simply calls getForceSubclass(),
    /// ignoring the sphere parameters.
    void                 getForceOnSphereSubclass(const SIM_Object &object,
                                        const UT_Vector3 &position,
                                        const fpreal radius,
                                        const UT_Vector3 &velocity,
                                        const UT_Vector3 &angvel,
                                        const fpreal mass,
                                        UT_Vector3 &force,
                                        UT_Vector3 &torque) const override;

private:
    /// Get the SIM_DopDescription for creating an orbit force.
    static const SIM_DopDescription     *getForceOrbitDopDescription();

    /// This macro adds the standard getCastToType() method needed by
    /// DECLARE_DATAFACTORY()
    DECLARE_STANDARD_GETCASTTOTYPE();
    /// This macro defines all the static functions needed to declare a
    /// SIM_DataFactory for SIM_ForceOrbit.
    DECLARE_DATAFACTORY(SIM_ForceOrbit,
                        SIM_Force,
                        "Orbit Force",
                        getForceOrbitDopDescription());
};

} // End HDK_Sample namespace

#endif