1 // Written by Andrew J. Ross, started December 2003
3 // Copyright (C) 2003 Andrew J. Ross - andy@plausible.org
5 // This library is free software; you can redistribute it and/or
6 // modify it under the terms of the GNU Library General Public
7 // License as published by the Free Software Foundation; either
8 // version 2 of the License, or (at your option) any later version.
10 // This library is distributed in the hope that it will be useful,
11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 // Library General Public License for more details.
15 // You should have received a copy of the GNU General Public License
16 // along with this program; if not, write to the Free Software
17 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
20 # include <simgear_config.h>
23 #include "interpolator.hxx"
25 #include <simgear/math/SGMath.hxx>
27 void SGInterpolator::addNew(SGPropertyNode* prop, int nPoints)
29 // Set the property type to a double, if it isn't already, and
30 // make sure we aren't already managing this node.
31 prop->setDoubleValue(prop->getDoubleValue());
34 Interp* iterp = new Interp();
36 iterp->nPoints = nPoints;
37 iterp->curve = new double[2*nPoints];
39 // Dirty trick: leave the new value sitting in _list to avoid
40 // having to return a pointer to a private type.
45 void SGInterpolator::interpolate(SGPropertyNode* prop, int nPoints,
46 double* values, double* deltas)
48 addNew(prop, nPoints);
49 for(int i=0; i<nPoints; i++) {
50 _list->dt(i) = deltas[i];
51 _list->val(i) = values[i];
55 void SGInterpolator::interpolate(SGPropertyNode* prop, double val, double dt)
63 // Delete all the list elements where "expr" is true.
65 // Silly preprocessor hack to avoid writing the linked list code in
66 // two places. You would think that an STL set would be the way to
67 // go, but I had terrible trouble getting it to work with the
68 // dynamically allocated "curve" member. Frankly, this is easier to
69 // write, and the code is smaller to boot...
71 #define DELETE_WHERE(EXPR)\
72 Interp *p = _list, **last = &_list; \
77 p = (*last) ? (*last)->next : 0; \
82 void SGInterpolator::cancel(SGPropertyNode* prop)
84 DELETE_WHERE(p->target == prop)
87 void SGInterpolator::update(double dt)
89 DELETE_WHERE(interp(p, dt))
92 // This is the where the only "real" work happens. Walk through the
93 // data points until we find one with some time left, slurp it up and
94 // repeat until we run out of dt.
95 bool SGInterpolator::interp(Interp* rec, double dt)
97 double val = rec->target->getDoubleValue();
99 for(i=0; i < rec->nPoints; i++) {
100 if(rec->dt(i) > 0 && dt < rec->dt(i)) {
101 val += (dt / rec->dt(i)) * (rec->val(i) - val);
108 rec->target->setDoubleValue(val);
110 // Return true if this one is done
111 return i == rec->nPoints;