126 lines
4.2 KiB
C++
126 lines
4.2 KiB
C++
#ifndef _RIGIDBODY_HPP
|
|
#define _RIGIDBODY_HPP
|
|
|
|
namespace yasim {
|
|
|
|
//
|
|
// A RigidBody object maintains all "internal" state about an object,
|
|
// accumulates force and torque information from external sources, and
|
|
// calculates the resulting accelerations.
|
|
//
|
|
//
|
|
// Units note: obviously, the choice of mass, time and distance units
|
|
// is up to the user. If you provide mass in kilograms, forces in
|
|
// newtons, and torques in newton-meters, you'll get your
|
|
// accelerations back in m/s^2. The angular units, however, are
|
|
// UNIFORMLY radians. Angular velocities are radians per <time unit>,
|
|
// the angular acceleration you get back is radians per <time unit>^2,
|
|
// and the angular momenta supplied to setGyro must be in radians,
|
|
// too. Radians, not degrees. Don't forget.
|
|
//
|
|
class RigidBody
|
|
{
|
|
public:
|
|
RigidBody();
|
|
~RigidBody();
|
|
|
|
// Adds a point mass to the system. Returns a handle so the gyro
|
|
// can be later modified via setMass().
|
|
int addMass(float mass, float* pos);
|
|
|
|
// Modifies a previously-added point mass (fuel tank running dry,
|
|
// gear going up, swing wing swinging, pilot bailing out, etc...)
|
|
void setMass(int handle, float mass);
|
|
void setMass(int handle, float mass, float* pos);
|
|
|
|
int numMasses();
|
|
float getMass(int handle);
|
|
void getMassPosition(int handle, float* out);
|
|
float getTotalMass();
|
|
|
|
// The velocity, in local coordinates, of the specified point on a
|
|
// body rotating about its c.g. with velocity rot.
|
|
void pointVelocity(float* pos, float* rot, float* out);
|
|
|
|
// Sets the "gyroscope" for the body. This is the total
|
|
// "intrinsic" angular momentum of the body; that is, rotations of
|
|
// sub-objects, NOT rotation of the whole body within the global
|
|
// frame. Because angular momentum is additive in this way, we
|
|
// don't need to specify specific gyro objects; just add all their
|
|
// momenta together and set it here.
|
|
void setGyro(float* angularMomentum);
|
|
|
|
|
|
// When masses are moved or changed, this object needs to
|
|
// regenerate its internal tables. This step is expensive, so
|
|
// it's exposed to the client who can amortize the call across
|
|
// multiple changes.
|
|
void recalc();
|
|
|
|
// Resets the current force/torque parameters to zero.
|
|
void reset();
|
|
|
|
|
|
// Applies a force at the specified position.
|
|
void addForce(float* pos, float* force);
|
|
|
|
// Applies a force at the center of gravity.
|
|
void addForce(float* force);
|
|
|
|
// Adds a torque with the specified axis and magnitude
|
|
void addTorque(float* torque);
|
|
|
|
// Sets the rotation rate of the body (about its c.g.) within the
|
|
// surrounding environment. This is needed to compute torque on
|
|
// the body due to the centripetal forces involved in the
|
|
// rotation. NOTE: the rotation vector, like all other
|
|
// coordinates used here, is specified IN THE LOCAL COORDINATE
|
|
// SYSTEM.
|
|
void setBodySpin(float* rotation);
|
|
|
|
|
|
|
|
// Returns the center of gravity of the masses, in the body
|
|
// coordinate system.
|
|
void getCG(float* cgOut);
|
|
|
|
// Returns the acceleration of the body's c.g. relative to the
|
|
// rest of the world, specified in local coordinates.
|
|
void getAccel(float* accelOut);
|
|
|
|
// Returns the acceleration of a specific location in local
|
|
// coordinates. If the body is rotating, this will be different
|
|
// from the c.g. acceleration due to the centripetal accelerations
|
|
// of points not on the rotation axis.
|
|
void getAccel(float* pos, float* accelOut);
|
|
|
|
// Returns the instantaneous rate of change of the angular
|
|
// velocity, as a vector in local coordinates.
|
|
void getAngularAccel(float* accelOut);
|
|
|
|
// Returns the intertia tensor in a float[9] allocated by caller.
|
|
void getInertiaMatrix(float* inertiaOut);
|
|
|
|
private:
|
|
struct Mass { float m; float p[3]; };
|
|
|
|
// Internal "rotational structure"
|
|
Mass* _masses;
|
|
int _nMasses;
|
|
int _massesAlloced;
|
|
float _totalMass;
|
|
float _cg[3];
|
|
float _gyro[3];
|
|
|
|
// Inertia tensor, and its inverse. Computed from the above.
|
|
float _tI[9];
|
|
float _invI[9];
|
|
|
|
// Externally determined quantities
|
|
float _force[3];
|
|
float _torque[3];
|
|
float _spin[3];
|
|
};
|
|
|
|
}; // namespace yasim
|
|
#endif // _RIGIDBODY_HPP
|