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|
/**
* $Id$
* Copyright (C) 2001 NaN Technologies B.V.
* The basic physics object.
*/
#ifdef WIN32
// This warning tells us about truncation of __long__ stl-generated names.
// It can occasionally cause DevStudio to have internal compiler warnings.
#pragma warning( disable : 4786 )
#endif
#include "SM_Object.h"
#include "SM_Scene.h"
#include "SM_FhObject.h"
#include "MT_MinMax.h"
// Tweak parameters
static MT_Scalar ImpulseThreshold = 0.5;
SM_Object::SM_Object(
DT_ShapeHandle shape,
const SM_MaterialProps *materialProps,
const SM_ShapeProps *shapeProps,
SM_Object *dynamicParent
) :
m_shape(shape),
m_materialProps(materialProps),
m_materialPropsBackup(0),
m_shapeProps(shapeProps),
m_shapePropsBackup(0),
m_dynamicParent(dynamicParent),
m_object(DT_CreateObject(this, shape)),
m_margin(0.0),
m_scaling(1.0, 1.0, 1.0),
m_reaction_impulse(0.0, 0.0, 0.0),
m_reaction_force(0.0, 0.0, 0.0),
m_kinematic(false),
m_prev_kinematic(false),
m_is_rigid_body(false),
m_lin_mom(0.0, 0.0, 0.0),
m_ang_mom(0.0, 0.0, 0.0),
m_force(0.0, 0.0, 0.0),
m_torque(0.0, 0.0, 0.0),
m_client_object(0),
m_fh_object(0),
m_combined_lin_vel (0.0, 0.0, 0.0),
m_combined_ang_vel (0.0, 0.0, 0.0)
{
m_xform.setIdentity();
m_xform.getValue(m_ogl_matrix);
if (shapeProps &&
(shapeProps->m_do_fh || shapeProps->m_do_rot_fh)) {
MT_Vector3 ray(0.0, 0.0, -10.0);
m_fh_object = new SM_FhObject(ray, this);
}
m_suspended = false;
}
void
SM_Object::
integrateForces(
MT_Scalar timeStep
){
if (!m_suspended) {
m_prev_state = *this;
m_prev_state.setLinearVelocity(actualLinVelocity());
m_prev_state.setAngularVelocity(actualAngVelocity());
if (isDynamic()) {
// Integrate momentum (forward Euler)
m_lin_mom += m_force * timeStep;
m_ang_mom += m_torque * timeStep;
// Drain momentum because of air/water resistance
m_lin_mom *= pow(m_shapeProps->m_lin_drag, timeStep);
m_ang_mom *= pow(m_shapeProps->m_ang_drag, timeStep);
// Set velocities according momentum
m_lin_vel = m_lin_mom / m_shapeProps->m_mass;
m_ang_vel = m_ang_mom / m_shapeProps->m_inertia;
}
}
};
void
SM_Object::
integrateMomentum(
MT_Scalar timeStep
){
// Integrate position and orientation
// only do it for objects with linear and/or angular velocity
// else clients with hierarchies may get into trouble
if (!actualLinVelocity().fuzzyZero() || !actualAngVelocity().fuzzyZero())
{
// those MIDPOINT and BACKWARD integration methods are
// in this form not ok with some testfiles !
// For a release build please use forward euler unless completely tested
//#define MIDPOINT
//#define BACKWARD
#ifdef MIDPOINT
// Midpoint rule
m_pos += (m_prev_state.getLinearVelocity() + actualLinVelocity()) * (timeStep * 0.5);
m_orn += (m_prev_state.getAngularVelocity() * m_prev_state.getOrientation() + actualAngVelocity() * m_orn) * (timeStep * 0.25);
#elif defined BACKWARD
// Backward Euler
m_pos += actualLinVelocity() * timeStep;
m_orn += actualAngVelocity() * m_orn * (timeStep * 0.5);
#else
// Forward Euler
m_pos += m_prev_state.getLinearVelocity() * timeStep;
m_orn += m_prev_state.getAngularVelocity() * m_orn * (timeStep * 0.5);
#endif
m_orn.normalize(); // I might not be necessary to do this every call
calcXform();
notifyClient();
}
}
void SM_Object::boing(
void *client_data,
void *object1,
void *object2,
const DT_CollData *coll_data
){
SM_Scene *scene = (SM_Scene *)client_data;
SM_Object *obj1 = (SM_Object *)object1;
SM_Object *obj2 = (SM_Object *)object2;
scene->addPair(obj1, obj2); // Record this collision for client callbacks
// If one of the objects is a ghost then ignore it for the dynamics
if (obj1->isGhost() || obj2->isGhost()) {
return;
}
if (!obj2->isDynamic()) {
std::swap(obj1, obj2);
}
if (!obj2->isDynamic()) {
return;
}
// obj1 points to a dynamic object
// This distinction between dynamic and non-dynamic objects should not be
// necessary. Non-dynamic objects are assumed to have infinite mass.
if (obj1->isDynamic()) {
// normal to the contact plane
MT_Vector3 normal = obj2->m_pos - obj1->m_pos;
MT_Scalar dist = normal.length();
if (MT_EPSILON < dist && dist <= obj1->getMargin() + obj2->getMargin())
{
normal /= dist;
// relative velocity of the contact points
MT_Vector3 rel_vel = obj2->actualLinVelocity() - obj1->actualLinVelocity();
// relative velocity projected onto the normal
MT_Scalar rel_vel_normal = normal.dot(rel_vel);
// if the objects are approaching eachother...
if (rel_vel_normal < 0.0) {
MT_Scalar restitution;
// ...and the approaching velocity is large enough...
if (-rel_vel_normal > ImpulseThreshold) {
// ...this must be a true collision.
restitution =
MT_min(obj1->getMaterialProps()->m_restitution,
obj2->getMaterialProps()->m_restitution);
}
else {
// otherwise, it is a resting contact, and thus the
// relative velocity must be made zero
restitution = 0.0;
// We also need to interfere with the positions of the
// objects, otherwise they might drift into eachother.
MT_Vector3 penalty = normal *
(0.5 * (obj1->getMargin() + obj2->getMargin() - dist));
obj1->m_pos -= penalty;
obj2->m_pos += penalty;
}
// Compute the impulse necessary to yield the desired relative velocity...
MT_Scalar impulse = -(1.0 + restitution) * rel_vel_normal /
(obj1->getInvMass() + obj2->getInvMass());
// ... and apply it.
obj1->applyCenterImpulse(-impulse * normal);
obj2->applyCenterImpulse( impulse * normal);
}
}
}
else {
// Same again but now obj1 is non-dynamic
// Compute the point on obj1 closest to obj2 (= sphere with radius = 0)
MT_Point3 local1, local2;
MT_Scalar dist = DT_GetClosestPair(obj1->m_object, obj2->m_object,
local1.getValue(), local2.getValue());
// local1 is th point closest to obj2
// local2 is the local origin of obj2
if (MT_EPSILON < dist && dist <= obj2->getMargin()) {
MT_Point3 world1 = obj1->getWorldCoord(local1);
MT_Point3 world2 = obj2->getWorldCoord(local2);
MT_Vector3 vel1 = obj1->getVelocity(local1) + obj1->m_combined_lin_vel;
MT_Vector3 vel2 = obj2->getVelocity(local2) + obj2->m_combined_lin_vel;
// the normal to the contact plane
MT_Vector3 normal = world2 - world1;
normal /= dist;
// wr2 points from obj2's origin to the global contact point
// wr2 is only needed for rigid bodies (objects for which the
// friction can change the angular momentum).
// vel2 is adapted to denote the velocity of the contact point
MT_Vector3 wr2;
if (obj2->isRigidBody()) {
wr2 = -obj2->getMargin() * normal;
vel2 += obj2->actualAngVelocity().cross(wr2);
}
// This should look familiar....
MT_Vector3 rel_vel = vel2 - vel1;
MT_Scalar rel_vel_normal = normal.dot(rel_vel);
if (rel_vel_normal < 0.0) {
MT_Scalar restitution;
if (-rel_vel_normal > ImpulseThreshold) {
restitution =
MT_min(obj1->getMaterialProps()->m_restitution,
obj2->getMaterialProps()->m_restitution);
}
else {
restitution = 0.0;
// We fix drift by moving obj2 only, since obj1 was
// non-dynamic.
obj2->m_pos += normal * (obj2->getMargin() - dist);
}
MT_Scalar impulse = -(1.0 + restitution) * rel_vel_normal /
(obj1->getInvMass() + obj2->getInvMass());
obj2->applyCenterImpulse( impulse * normal);
// The friction part starts here!!!!!!!!
// Compute the lateral component of the relative velocity
// lateral actually points in the opposite direction, i.e.,
// into the direction of the friction force.
#if 1
// test - only do friction on the physics part of the
// velocity.
vel1 -= obj1->m_combined_lin_vel;
vel2 -= obj2->m_combined_lin_vel;
// This should look familiar....
rel_vel = vel2 - vel1;
rel_vel_normal = normal.dot(rel_vel);
#endif
MT_Vector3 lateral = normal * rel_vel_normal - rel_vel;
const SM_ShapeProps *shapeProps = obj2->getShapeProps();
if (shapeProps->m_do_anisotropic) {
// For anisotropic friction we scale the lateral component,
// rather than compute a direction-dependent fricition
// factor. For this the lateral component is transformed to
// local coordinates.
MT_Matrix3x3 lcs(obj2->m_orn);
// We cannot use m_xform.getBasis() for the matrix, since
// it might contain a non-uniform scaling.
// OPT: it's a bit daft to compute the matrix since the
// quaternion itself can be used to do the transformation.
MT_Vector3 loc_lateral = lateral * lcs;
// lcs is orthogonal so lcs.inversed() == lcs.transposed(),
// and lcs.transposed() * lateral == lateral * lcs.
const MT_Vector3& friction_scaling =
shapeProps->m_friction_scaling;
// Scale the local lateral...
loc_lateral.scale(friction_scaling[0],
friction_scaling[1],
friction_scaling[2]);
// ... and transform it back to global coordinates
lateral = lcs * loc_lateral;
}
// A tiny Coulomb friction primer:
// The Coulomb friction law states that the magnitude of the
// maximum possible friction force depends linearly on the
// magnitude of the normal force.
//
// F_max_friction = friction_factor * F_normal
//
// (NB: independent of the contact area!!)
//
// The friction factor depends on the material.
// We use impulses rather than forces but let us not be
// bothered by this.
MT_Scalar rel_vel_lateral = lateral.length();
if (rel_vel_lateral > MT_EPSILON) {
lateral /= rel_vel_lateral;
MT_Scalar friction_factor =
MT_min(obj1->getMaterialProps()->m_friction,
obj2->getMaterialProps()->m_friction);
// Compute the maximum friction impulse
MT_Scalar max_friction =
friction_factor * MT_max(0.0, impulse);
// I guess the GEN_max is not necessary, so let's check it
assert(impulse >= 0.0);
// Here's the trick. We compute the impulse to make the
// lateral velocity zero. (Make the objects stick together
// at the contact point. If this impulse is larger than
// the maximum possible friction impulse, then shrink its
// magnitude to the maximum friction.
if (obj2->isRigidBody()) {
// For rigid bodies we take the inertia into account,
// since the friciton impulse is going to change the
// angular momentum as well.
MT_Scalar impulse_lateral = rel_vel_lateral /
(obj1->getInvMass() + obj2->getInvMass() +
((obj2->getInvInertia() * wr2.cross(lateral)).cross(wr2)).dot(lateral));
MT_Scalar friction = MT_min(impulse_lateral, max_friction);
obj2->applyImpulse(world2 + wr2, friction * lateral);
}
else {
MT_Scalar impulse_lateral = rel_vel_lateral /
(obj1->getInvMass() + obj2->getInvMass());
MT_Scalar friction = MT_min(impulse_lateral, max_friction);
obj2->applyCenterImpulse( friction * lateral);
}
}
obj2->calcXform();
obj2->notifyClient();
}
}
}
}
SM_Object::SM_Object(
) {
// warning no initialization of variables done by moto.
}
SM_Object::
~SM_Object() {
delete m_fh_object;
DT_DeleteObject(m_object);
}
bool
SM_Object::
isDynamic(
) const {
return m_shapeProps != 0;
}
/* nzc experimental. There seem to be two places where kinematics
* are evaluated: proceedKinematic (called from SM_Scene) and
* proceed() in this object. I'll just try and bunge these out for
* now. */
void
SM_Object::
suspend(
){
if (!m_suspended) {
m_suspended = true;
suspendDynamics();
}
}
void
SM_Object::
resume(
) {
if (m_suspended) {
m_suspended = false;
restoreDynamics();
}
}
void
SM_Object::
suspendDynamics(
) {
if (m_shapeProps) {
m_shapePropsBackup = m_shapeProps;
m_shapeProps = 0;
}
}
void
SM_Object::
restoreDynamics(
) {
if (m_shapePropsBackup) {
m_shapeProps = m_shapePropsBackup;
m_shapePropsBackup = 0;
}
}
bool
SM_Object::
isGhost(
) const {
return m_materialProps == 0;
}
void
SM_Object::
suspendMaterial(
) {
if (m_materialProps) {
m_materialPropsBackup = m_materialProps;
m_materialProps = 0;
}
}
void
SM_Object::
restoreMaterial(
) {
if (m_materialPropsBackup) {
m_materialProps = m_materialPropsBackup;
m_materialPropsBackup = 0;
}
}
SM_FhObject *
SM_Object::
getFhObject(
) const {
return m_fh_object;
}
void
SM_Object::
registerCallback(
SM_Callback& callback
) {
m_callbackList.push_back(&callback);
}
// Set the local coordinate system according to the current state
void
SM_Object::
calcXform() {
m_xform.setOrigin(m_pos);
m_xform.setBasis(MT_Matrix3x3(m_orn, m_scaling));
m_xform.getValue(m_ogl_matrix);
DT_SetMatrixd(m_object, m_ogl_matrix);
if (m_fh_object) {
m_fh_object->setPosition(m_pos);
m_fh_object->calcXform();
}
}
// Call callbacks to notify the client of a change of placement
void
SM_Object::
notifyClient() {
T_CallbackList::iterator i;
for (i = m_callbackList.begin(); i != m_callbackList.end(); ++i) {
(*i)->do_me();
}
}
// Save the current state information for use in the velocity computation in the next frame.
void
SM_Object::
proceedKinematic(
MT_Scalar timeStep
) {
/* nzc: need to bunge this for the logic bubbling as well? */
if (!m_suspended) {
m_prev_kinematic = m_kinematic;
if (m_kinematic) {
m_prev_xform = m_xform;
m_timeStep = timeStep;
calcXform();
m_kinematic = false;
}
}
}
void
SM_Object::
saveReactionForce(
MT_Scalar timeStep
) {
if (isDynamic()) {
m_reaction_force = m_reaction_impulse / timeStep;
m_reaction_impulse.setValue(0.0, 0.0, 0.0);
}
}
void
SM_Object::
clearForce(
) {
m_force.setValue(0.0, 0.0, 0.0);
m_torque.setValue(0.0, 0.0, 0.0);
}
void
SM_Object::
clearMomentum(
) {
m_lin_mom.setValue(0.0, 0.0, 0.0);
m_ang_mom.setValue(0.0, 0.0, 0.0);
}
void
SM_Object::
setMargin(
MT_Scalar margin
) {
m_margin = margin;
DT_SetMargin(m_object, margin);
}
MT_Scalar
SM_Object::
getMargin(
) const {
return m_margin;
}
const
SM_MaterialProps *
SM_Object::
getMaterialProps(
) const {
return m_materialProps;
}
const
SM_ShapeProps *
SM_Object::
getShapeProps(
) const {
return m_shapeProps;
}
void
SM_Object::
setPosition(
const MT_Point3& pos
){
m_kinematic = true;
m_pos = pos;
}
void
SM_Object::
setOrientation(
const MT_Quaternion& orn
){
assert(!orn.fuzzyZero());
m_kinematic = true;
m_orn = orn;
}
void
SM_Object::
setScaling(
const MT_Vector3& scaling
){
m_kinematic = true;
m_scaling = scaling;
}
/**
* Functions to handle linear velocity
*/
void
SM_Object::
setExternalLinearVelocity(
const MT_Vector3& lin_vel
) {
m_combined_lin_vel=lin_vel;
}
void
SM_Object::
addExternalLinearVelocity(
const MT_Vector3& lin_vel
) {
m_combined_lin_vel+=lin_vel;
}
void
SM_Object::
addLinearVelocity(
const MT_Vector3& lin_vel
){
m_lin_vel += lin_vel;
if (m_shapeProps) {
m_lin_mom = m_lin_vel * m_shapeProps->m_mass;
}
}
void
SM_Object::
setLinearVelocity(
const MT_Vector3& lin_vel
){
m_lin_vel = lin_vel;
if (m_shapeProps) {
m_lin_mom = m_lin_vel * m_shapeProps->m_mass;
}
}
/**
* Functions to handle angular velocity
*/
void
SM_Object::
setExternalAngularVelocity(
const MT_Vector3& ang_vel
) {
m_combined_ang_vel = ang_vel;
}
void
SM_Object::
addExternalAngularVelocity(
const MT_Vector3& ang_vel
) {
m_combined_ang_vel += ang_vel;
}
void
SM_Object::
setAngularVelocity(
const MT_Vector3& ang_vel
) {
m_ang_vel = ang_vel;
if (m_shapeProps) {
m_ang_mom = m_ang_vel * m_shapeProps->m_inertia;
}
}
void
SM_Object::
addAngularVelocity(
const MT_Vector3& ang_vel
) {
m_ang_vel += ang_vel;
if (m_shapeProps) {
m_ang_mom = m_ang_vel * m_shapeProps->m_inertia;
}
}
void
SM_Object::
clearCombinedVelocities(
) {
m_combined_lin_vel = MT_Vector3(0,0,0);
m_combined_ang_vel = MT_Vector3(0,0,0);
}
void
SM_Object::
resolveCombinedVelocities(
const MT_Vector3 & lin_vel,
const MT_Vector3 & ang_vel
) {
// Different behaviours for dynamic and non-dynamic
// objects. For non-dynamic we just set the velocity to
// zero. For dynmic the physics velocity has to be
// taken into account. We must make an arbitrary decision
// on how to resolve the 2 velocities. Choices are
// Add the physics velocity to the linear velocity. Objects
// will just keep on moving in the direction they were
// last set in - untill external forces affect them.
// Set the combinbed linear and physics velocity to zero.
// Set the physics velocity in the direction of the set velocity
// zero.
if (isDynamic()) {
#if 1
m_lin_vel += lin_vel;
m_ang_vel += ang_vel;
#else
//compute the component of the physics velocity in the
// direction of the set velocity and set it to zero.
MT_Vector3 lin_vel_norm = lin_vel.normalized();
m_lin_vel -= (m_lin_vel.dot(lin_vel_norm) * lin_vel_norm);
#endif
m_lin_mom = m_lin_vel * m_shapeProps->m_mass;
m_ang_mom = m_ang_vel * m_shapeProps->m_inertia;
clearCombinedVelocities();
}
}
MT_Scalar
SM_Object::
getInvMass(
) const {
return m_shapeProps ? 1.0 / m_shapeProps->m_mass : 0.0;
// OPT: cache the result of this division rather than compute it each call
}
MT_Scalar
SM_Object::
getInvInertia(
) const {
return m_shapeProps ? 1.0 / m_shapeProps->m_inertia : 0.0;
// OPT: cache the result of this division rather than compute it each call
}
void
SM_Object::
applyForceField(
const MT_Vector3& accel
) {
if (m_shapeProps) {
m_force += m_shapeProps->m_mass * accel; // F = m * a
}
}
void
SM_Object::
applyCenterForce(
const MT_Vector3& force
) {
m_force += force;
}
void
SM_Object::
applyTorque(
const MT_Vector3& torque
) {
m_torque += torque;
}
void
SM_Object::
applyImpulse(
const MT_Point3& attach, const MT_Vector3& impulse
) {
applyCenterImpulse(impulse); // Change in linear momentum
applyAngularImpulse((attach - m_pos).cross(impulse)); // Change in angular momentump
}
void
SM_Object::
applyCenterImpulse(
const MT_Vector3& impulse
) {
if (m_shapeProps) {
m_lin_mom += impulse;
m_reaction_impulse += impulse;
m_lin_vel = m_lin_mom / m_shapeProps->m_mass;
// The linear velocity is immedialtely updated since otherwise
// simultaneous collisions will get a double impulse.
}
}
void
SM_Object::
applyAngularImpulse(
const MT_Vector3& impulse
) {
if (m_shapeProps) {
m_ang_mom += impulse;
m_ang_vel = m_ang_mom / m_shapeProps->m_inertia;
}
}
MT_Point3
SM_Object::
getWorldCoord(
const MT_Point3& local
) const {
return m_xform(local);
}
MT_Vector3
SM_Object::
getVelocity(
const MT_Point3& local
) const {
// For displaced objects the velocity is faked using the previous state.
// Dynamic objects get their own velocity, not the faked velocity.
// (Dynamic objects shouldn't be displaced in the first place!!)
return m_prev_kinematic && !isDynamic() ?
(m_xform(local) - m_prev_xform(local)) / m_timeStep :
m_lin_vel + m_ang_vel.cross(m_xform.getBasis() * local);
// NB: m_xform.getBasis() * local == m_xform(local) - m_xform.getOrigin()
}
const
MT_Vector3&
SM_Object::
getReactionForce(
) const {
return m_reaction_force;
}
void
SM_Object::
getMatrix(
double *m
) const {
std::copy(&m_ogl_matrix[0], &m_ogl_matrix[16], &m[0]);
}
const
double *
SM_Object::
getMatrix(
) const {
return m_ogl_matrix;
}
// Still need this???
const
MT_Transform&
SM_Object::
getScaledTransform(
) const {
return m_xform;
}
DT_ObjectHandle
SM_Object::
getObjectHandle(
) const {
return m_object;
}
DT_ShapeHandle
SM_Object::
getShapeHandle(
) const {
return m_shape;
}
void
SM_Object::
setClientObject(
void *clientobj
) {
m_client_object = clientobj;
}
void *
SM_Object::
getClientObject(
){
return m_client_object;
}
SM_Object *
SM_Object::
getDynamicParent(
) {
return m_dynamicParent;
}
void
SM_Object::
setRigidBody(
bool is_rigid_body
) {
m_is_rigid_body = is_rigid_body;
}
bool
SM_Object::
isRigidBody(
) const {
return m_is_rigid_body;
}
const
MT_Vector3
SM_Object::
actualLinVelocity(
) const {
return m_combined_lin_vel + m_lin_vel;
};
const
MT_Vector3
SM_Object::
actualAngVelocity(
) const {
return m_combined_ang_vel + m_ang_vel;
};
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