/*************************************************************************
* *
* Open Dynamics Engine, Copyright (C) 2001,2002 Russell L. Smith. *
* All rights reserved. Email: russ@q12.org Web: www.q12.org *
* *
* This library is free software; you can redistribute it and/or *
* modify it under the terms of EITHER: *
* (1) The GNU Lesser General Public License as published by the Free *
* Software Foundation; either version 2.1 of the License, or (at *
* your option) any later version. The text of the GNU Lesser *
* General Public License is included with this library in the *
* file LICENSE.TXT. *
* (2) The BSD-style license that is included with this library in *
* the file LICENSE-BSD.TXT. *
* *
* This library is distributed in the hope that it will be useful, *
* but WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the files *
* LICENSE.TXT and LICENSE-BSD.TXT for more details. *
* *
*************************************************************************/
#include "ode/ode.h"
#include "objects.h"
#include "joint.h"
#include "util.h"
#define ALLOCA dALLOCA16
//****************************************************************************
// Auto disabling
void dInternalHandleAutoDisabling (dxWorld *world, dReal stepsize)
{
dxBody *bb;
for (bb=world->firstbody; bb; bb=(dxBody*)bb->next) {
// nothing to do unless this body is currently enabled and has
// the auto-disable flag set
if ((bb->flags & (dxBodyAutoDisable|dxBodyDisabled)) != dxBodyAutoDisable) continue;
// see if the body is idle
int idle = 1; // initial assumption
dReal lspeed2 = dDOT(bb->lvel,bb->lvel);
if (lspeed2 > bb->adis.linear_threshold) {
idle = 0; // moving fast - not idle
}
else {
dReal aspeed = dDOT(bb->avel,bb->avel);
if (aspeed > bb->adis.angular_threshold) {
idle = 0; // turning fast - not idle
}
}
// if it's idle, accumulate steps and time.
// these counters won't overflow because this code doesn't run for disabled bodies.
if (idle) {
bb->adis_stepsleft--;
bb->adis_timeleft -= stepsize;
}
else {
bb->adis_stepsleft = bb->adis.idle_steps;
bb->adis_timeleft = bb->adis.idle_time;
}
// disable the body if it's idle for a long enough time
if (bb->adis_stepsleft < 0 && bb->adis_timeleft < 0) {
bb->flags |= dxBodyDisabled;
}
}
}
//****************************************************************************
// body rotation
// return sin(x)/x. this has a singularity at 0 so special handling is needed
// for small arguments.
static inline dReal sinc (dReal x)
{
// if |x| < 1e-4 then use a taylor series expansion. this two term expansion
// is actually accurate to one LS bit within this range if double precision
// is being used - so don't worry!
if (dFabs(x) < 1.0e-4) return REAL(1.0) - x*x*REAL(0.166666666666666666667);
else return dSin(x)/x;
}
// given a body b, apply its linear and angular rotation over the time
// interval h, thereby adjusting its position and orientation.
void dxStepBody (dxBody *b, dReal h)
{
int j;
// handle linear velocity
for (j=0; j<3; j++) b->posr.pos[j] += h * b->lvel[j];
if (b->flags & dxBodyFlagFiniteRotation) {
dVector3 irv; // infitesimal rotation vector
dQuaternion q; // quaternion for finite rotation
if (b->flags & dxBodyFlagFiniteRotationAxis) {
// split the angular velocity vector into a component along the finite
// rotation axis, and a component orthogonal to it.
dVector3 frv; // finite rotation vector
dReal k = dDOT (b->finite_rot_axis,b->avel);
frv[0] = b->finite_rot_axis[0] * k;
frv[1] = b->finite_rot_axis[1] * k;
frv[2] = b->finite_rot_axis[2] * k;
irv[0] = b->avel[0] - frv[0];
irv[1] = b->avel[1] - frv[1];
irv[2] = b->avel[2] - frv[2];
// make a rotation quaternion q that corresponds to frv * h.
// compare this with the full-finite-rotation case below.
h *= REAL(0.5);
dReal theta = k * h;
q[0] = dCos(theta);
dReal s = sinc(theta) * h;
q[1] = frv[0] * s;
q[2] = frv[1] * s;
q[3] = frv[2] * s;
}
else {
// make a rotation quaternion q that corresponds to w * h
dReal wlen = dSqrt (b->avel[0]*b->avel[0] + b->avel[1]*b->avel[1] +
b->avel[2]*b->avel[2]);
h *= REAL(0.5);
dReal theta = wlen * h;
q[0] = dCos(theta);
dReal s = sinc(theta) * h;
q[1] = b->avel[0] * s;
q[2] = b->avel[1] * s;
q[3] = b->avel[2] * s;
}
// do the finite rotation
dQuaternion q2;
dQMultiply0 (q2,q,b->q);
for (j=0; j<4; j++) b->q[j] = q2[j];
// do the infitesimal rotation if required
if (b->flags & dxBodyFlagFiniteRotationAxis) {
dReal dq[4];
dWtoDQ (irv,b->q,dq);
for (j=0; j<4; j++) b->q[j] += h * dq[j];
}
}
else {
// the normal way - do an infitesimal rotation
dReal dq[4];
dWtoDQ (b->avel,b->q,dq);
for (j=0; j<4; j++) b->q[j] += h * dq[j];
}
// normalize the quaternion and convert it to a rotation matrix
dNormalize4 (b->q);
dQtoR (b->q,b->posr.R);
// notify all attached geoms that this body has moved
for (dxGeom *geom = b->geom; geom; geom = dGeomGetBodyNext (geom))
dGeomMoved (geom);
}
//****************************************************************************
// island processing
// this groups all joints and bodies in a world into islands. all objects
// in an island are reachable by going through connected bodies and joints.
// each island can be simulated separately.
// note that joints that are not attached to anything will not be included
// in any island, an so they do not affect the simulation.
//
// this function starts new island from unvisited bodies. however, it will
// never start a new islands from a disabled body. thus islands of disabled
// bodies will not be included in the simulation. disabled bodies are
// re-enabled if they are found to be part of an active island.
void dxProcessIslands (dxWorld *world, dReal stepsize, dstepper_fn_t stepper)
{
dxBody *b,*bb,**body;
dxJoint *j,**joint;
// nothing to do if no bodies
if (world->nb <= 0) return;
// handle auto-disabling of bodies
dInternalHandleAutoDisabling (world,stepsize);
// make arrays for body and joint lists (for a single island) to go into
body = (dxBody**) ALLOCA (world->nb * sizeof(dxBody*));
joint = (dxJoint**) ALLOCA (world->nj * sizeof(dxJoint*));
int bcount = 0; // number of bodies in `body'
int jcount = 0; // number of joints in `joint'
// set all body/joint tags to 0
for (b=world->firstbody; b; b=(dxBody*)b->next) b->tag = 0;
for (j=world->firstjoint; j; j=(dxJoint*)j->next) j->tag = 0;
// allocate a stack of unvisited bodies in the island. the maximum size of
// the stack can be the lesser of the number of bodies or joints, because
// new bodies are only ever added to the stack by going through untagged
// joints. all the bodies in the stack must be tagged!
int stackalloc = (world->nj < world->nb) ? world->nj : world->nb;
dxBody **stack = (dxBody**) ALLOCA (stackalloc * sizeof(dxBody*));
for (bb=world->firstbody; bb; bb=(dxBody*)bb->next) {
// get bb = the next enabled, untagged body, and tag it
if (bb->tag || (bb->flags & dxBodyDisabled)) continue;
bb->tag = 1;
// tag all bodies and joints starting from bb.
int stacksize = 0;
b = bb;
body[0] = bb;
bcount = 1;
jcount = 0;
goto quickstart;
while (stacksize > 0) {
b = stack[--stacksize]; // pop body off stack
body[bcount++] = b; // put body on body list
quickstart:
// traverse and tag all body's joints, add untagged connected bodies
// to stack
for (dxJointNode *n=b->firstjoint; n; n=n->next) {
if (!n->joint->tag) {
n->joint->tag = 1;
joint[jcount++] = n->joint;
if (n->body && !n->body->tag) {
n->body->tag = 1;
stack[stacksize++] = n->body;
}
}
}
dIASSERT(stacksize <= world->nb);
dIASSERT(stacksize <= world->nj);
}
// now do something with body and joint lists
stepper (world,body,bcount,joint,jcount,stepsize);
// what we've just done may have altered the body/joint tag values.
// we must make sure that these tags are nonzero.
// also make sure all bodies are in the enabled state.
int i;
for (i=0; i<bcount; i++) {
body[i]->tag = 1;
body[i]->flags &= ~dxBodyDisabled;
}
for (i=0; i<jcount; i++) joint[i]->tag = 1;
}
// if debugging, check that all objects (except for disabled bodies,
// unconnected joints, and joints that are connected to disabled bodies)
// were tagged.
# ifndef dNODEBUG
for (b=world->firstbody; b; b=(dxBody*)b->next) {
if (b->flags & dxBodyDisabled) {
if (b->tag) dDebug (0,"disabled body tagged");
}
else {
if (!b->tag) dDebug (0,"enabled body not tagged");
}
}
for (j=world->firstjoint; j; j=(dxJoint*)j->next) {
if ((j->node[0].body && (j->node[0].body->flags & dxBodyDisabled)==0) ||
(j->node[1].body && (j->node[1].body->flags & dxBodyDisabled)==0)) {
if (!j->tag) dDebug (0,"attached enabled joint not tagged");
}
else {
if (j->tag) dDebug (0,"unattached or disabled joint tagged");
}
}
# endif
}
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