1 /* Copyright 2002-2016 CS Systèmes d'Information
2 * Licensed to CS Systèmes d'Information (CS) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * CS licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 package org.orekit.frames;
19
20 import java.io.Serializable;
21 import java.util.ArrayList;
22 import java.util.List;
23
24 import org.orekit.errors.OrekitException;
25 import org.orekit.errors.OrekitExceptionWrapper;
26 import org.orekit.time.AbsoluteDate;
27 import org.orekit.utils.AngularDerivativesFilter;
28 import org.orekit.utils.CartesianDerivativesFilter;
29 import org.orekit.utils.GenericTimeStampedCache;
30 import org.orekit.utils.TimeStampedGenerator;
31
32 /** Transform provider using thread-safe interpolation on transforms sample.
33 * <p>
34 * The interpolation is a polynomial Hermite interpolation, which
35 * can either use or ignore the derivatives provided by the raw
36 * provider. This means that simple raw providers that do not compute
37 * derivatives can be used, the derivatives will be added appropriately
38 * by the interpolation process.
39 * </p>
40 * @see GenericTimeStampedCache
41 * @see ShiftingTransformProvider
42 * @author Luc Maisonobe
43 */
44 public class InterpolatingTransformProvider implements TransformProvider {
45
46 /** Serializable UID. */
47 private static final long serialVersionUID = 20140723L;
48
49 /** Provider for raw (non-interpolated) transforms. */
50 private final TransformProvider rawProvider;
51
52 /** Filter for Cartesian derivatives to use in interpolation. */
53 private final CartesianDerivativesFilter cFilter;
54
55 /** Filter for angular derivatives to use in interpolation. */
56 private final AngularDerivativesFilter aFilter;
57
58 /** Earliest supported date. */
59 private final AbsoluteDate earliest;
60
61 /** Latest supported date. */
62 private final AbsoluteDate latest;
63
64 /** Grid points time step. */
65 private final double step;
66
67 /** Cache for sample points. */
68 private final transient GenericTimeStampedCache<Transform> cache;
69
70 /** Simple constructor.
71 * @param rawProvider provider for raw (non-interpolated) transforms
72 * @param cFilter filter for derivatives from the sample to use in interpolation
73 * @param aFilter filter for derivatives from the sample to use in interpolation
74 * @param earliest earliest supported date
75 * @param latest latest supported date
76 * @param gridPoints number of interpolation grid points
77 * @param step grid points time step
78 * @param maxSlots maximum number of independent cached time slots
79 * in the {@link GenericTimeStampedCache time-stamped cache}
80 * @param maxSpan maximum duration span in seconds of one slot
81 * in the {@link GenericTimeStampedCache time-stamped cache}
82 * @param newSlotInterval time interval above which a new slot is created
83 * in the {@link GenericTimeStampedCache time-stamped cache}
84 */
85 public InterpolatingTransformProvider(final TransformProvider rawProvider,
86 final CartesianDerivativesFilter cFilter,
87 final AngularDerivativesFilter aFilter,
88 final AbsoluteDate earliest, final AbsoluteDate latest,
89 final int gridPoints, final double step,
90 final int maxSlots, final double maxSpan, final double newSlotInterval) {
91 this.rawProvider = rawProvider;
92 this.cFilter = cFilter;
93 this.aFilter = aFilter;
94 this.earliest = earliest;
95 this.latest = latest;
96 this.step = step;
97 this.cache = new GenericTimeStampedCache<Transform>(gridPoints, maxSlots, maxSpan, newSlotInterval,
98 new Generator(), Transform.class);
99 }
100
101 /** Get the underlying provider for raw (non-interpolated) transforms.
102 * @return provider for raw (non-interpolated) transforms
103 */
104 public TransformProvider getRawProvider() {
105 return rawProvider;
106 }
107
108 /** Get the number of interpolation grid points.
109 * @return number of interpolation grid points
110 */
111 public int getGridPoints() {
112 return cache.getNeighborsSize();
113 }
114
115 /** Get the grid points time step.
116 * @return grid points time step
117 */
118 public double getStep() {
119 return step;
120 }
121
122 /** {@inheritDoc} */
123 public Transform getTransform(final AbsoluteDate date) throws OrekitException {
124 try {
125
126 // retrieve a sample from the thread-safe cache
127 final List<Transform> sample = cache.getNeighbors(date);
128
129 // interpolate to specified date
130 return Transform.interpolate(date, cFilter, aFilter, sample);
131
132 } catch (OrekitExceptionWrapper oew) {
133 // something went wrong while generating the sample,
134 // we just forward the exception up
135 throw oew.getException();
136 }
137 }
138
139 /** Replace the instance with a data transfer object for serialization.
140 * <p>
141 * This intermediate class serializes only the data needed for generation,
142 * but does <em>not</em> serializes the cache itself (in fact the cache is
143 * not serializable).
144 * </p>
145 * @return data transfer object that will be serialized
146 */
147 private Object writeReplace() {
148 return new DTO(rawProvider, cFilter.getMaxOrder(), aFilter.getMaxOrder(),
149 earliest, latest, cache.getNeighborsSize(), step,
150 cache.getMaxSlots(), cache.getMaxSpan(), cache.getNewSlotQuantumGap());
151 }
152
153 /** Internal class used only for serialization. */
154 private static class DTO implements Serializable {
155
156 /** Serializable UID. */
157 private static final long serialVersionUID = 20140723L;
158
159 /** Provider for raw (non-interpolated) transforms. */
160 private final TransformProvider rawProvider;
161
162 /** Cartesian derivatives to use in interpolation. */
163 private final int cDerivatives;
164
165 /** Angular derivatives to use in interpolation. */
166 private final int aDerivatives;
167
168 /** Earliest supported date. */
169 private final AbsoluteDate earliest;
170
171 /** Latest supported date. */
172 private final AbsoluteDate latest;
173
174 /** Number of grid points. */
175 private final int gridPoints;
176
177 /** Grid points time step. */
178 private final double step;
179
180 /** Maximum number of independent cached time slots. */
181 private final int maxSlots;
182
183 /** Maximum duration span in seconds of one slot. */
184 private final double maxSpan;
185
186 /** Time interval above which a new slot is created. */
187 private final double newSlotInterval;
188
189 /** Simple constructor.
190 * @param rawProvider provider for raw (non-interpolated) transforms
191 * @param cDerivatives derivation order for Cartesian coordinates
192 * @param aDerivatives derivation order for angular coordinates
193 * @param earliest earliest supported date
194 * @param latest latest supported date
195 * @param gridPoints number of interpolation grid points
196 * @param step grid points time step
197 * @param maxSlots maximum number of independent cached time slots
198 * in the {@link GenericTimeStampedCache time-stamped cache}
199 * @param maxSpan maximum duration span in seconds of one slot
200 * in the {@link GenericTimeStampedCache time-stamped cache}
201 * @param newSlotInterval time interval above which a new slot is created
202 * in the {@link GenericTimeStampedCache time-stamped cache}
203 */
204 private DTO(final TransformProvider rawProvider, final int cDerivatives, final int aDerivatives,
205 final AbsoluteDate earliest, final AbsoluteDate latest,
206 final int gridPoints, final double step,
207 final int maxSlots, final double maxSpan, final double newSlotInterval) {
208 this.rawProvider = rawProvider;
209 this.cDerivatives = cDerivatives;
210 this.aDerivatives = aDerivatives;
211 this.earliest = earliest;
212 this.latest = latest;
213 this.gridPoints = gridPoints;
214 this.step = step;
215 this.maxSlots = maxSlots;
216 this.maxSpan = maxSpan;
217 this.newSlotInterval = newSlotInterval;
218 }
219
220 /** Replace the deserialized data transfer object with a {@link InterpolatingTransformProvider}.
221 * @return replacement {@link InterpolatingTransformProvider}
222 */
223 private Object readResolve() {
224 // build a new provider, with an empty cache
225 return new InterpolatingTransformProvider(rawProvider,
226 CartesianDerivativesFilter.getFilter(cDerivatives),
227 AngularDerivativesFilter.getFilter(aDerivatives),
228 earliest, latest, gridPoints, step,
229 maxSlots, maxSpan, newSlotInterval);
230 }
231
232 }
233
234 /** Local generator for thread-safe cache. */
235 private class Generator implements TimeStampedGenerator<Transform> {
236
237 /** {@inheritDoc} */
238 public List<Transform> generate(final Transform existing, final AbsoluteDate date) {
239
240 try {
241 final List<Transform> generated = new ArrayList<Transform>();
242
243 if (existing == null) {
244
245 // no prior existing transforms, just generate a first set
246 for (int i = 0; i < cache.getNeighborsSize(); ++i) {
247 generated.add(rawProvider.getTransform(date.shiftedBy(i * step)));
248 }
249
250 } else {
251
252 // some transforms have already been generated
253 // add the missing ones up to specified date
254
255 AbsoluteDate t = existing.getDate();
256 if (date.compareTo(t) > 0) {
257 // forward generation
258 do {
259 t = t.shiftedBy(step);
260 generated.add(generated.size(), rawProvider.getTransform(t));
261 } while (t.compareTo(date) <= 0);
262 } else {
263 // backward generation
264 do {
265 t = t.shiftedBy(-step);
266 generated.add(0, rawProvider.getTransform(t));
267 } while (t.compareTo(date) >= 0);
268 }
269 }
270
271 // return the generated transforms
272 return generated;
273 } catch (OrekitException oe) {
274 throw new OrekitExceptionWrapper(oe);
275 }
276
277 }
278
279 }
280
281 }