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Java Source Code / Java Documentation » 6.0 JDK Modules » java 3d » com.sun.j3d.utils.compression 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:         * $RCSfile: CompressionStreamNormal.java,v $
003:         *
004:         * Copyright (c) 2007 Sun Microsystems, Inc. All rights reserved.
005:         *
006:         * Redistribution and use in source and binary forms, with or without
007:         * modification, are permitted provided that the following conditions
008:         * are met:
009:         *
010:         * - Redistribution of source code must retain the above copyright
011:         *   notice, this list of conditions and the following disclaimer.
012:         *
013:         * - Redistribution in binary form must reproduce the above copyright
014:         *   notice, this list of conditions and the following disclaimer in
015:         *   the documentation and/or other materials provided with the
016:         *   distribution.
017:         *
018:         * Neither the name of Sun Microsystems, Inc. or the names of
019:         * contributors may be used to endorse or promote products derived
020:         * from this software without specific prior written permission.
021:         *
022:         * This software is provided "AS IS," without a warranty of any
023:         * kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND
024:         * WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY,
025:         * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY
026:         * EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN") AND ITS LICENSORS SHALL
027:         * NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF
028:         * USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
029:         * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR
030:         * ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL,
031:         * CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND
032:         * REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF THE USE OF OR
033:         * INABILITY TO USE THIS SOFTWARE, EVEN IF SUN HAS BEEN ADVISED OF THE
034:         * POSSIBILITY OF SUCH DAMAGES.
035:         *
036:         * You acknowledge that this software is not designed, licensed or
037:         * intended for use in the design, construction, operation or
038:         * maintenance of any nuclear facility.
039:         *
040:         * $Revision: 1.5 $
041:         * $Date: 2007/02/09 17:20:16 $
042:         * $State: Exp $
043:         */
044:
045:        package com.sun.j3d.utils.compression;
046:
047:        import javax.vecmath.Vector3f;
048:
049:        /**
050:         * This class represents a normal in a compression stream. It maintains both
051:         * floating-point and quantized representations.  This normal may be bundled
052:         * with a vertex or exist separately as a global normal.
053:         */
054:        class CompressionStreamNormal extends CompressionStreamElement {
055:            private int u, v;
056:            private int specialOctant, specialSextant;
057:            private float normalX, normalY, normalZ;
058:
059:            int octant, sextant;
060:            boolean specialNormal;
061:            int uAbsolute, vAbsolute;
062:
063:            /**
064:             * Create a CompressionStreamNormal.
065:             *
066:             * @param stream CompressionStream associated with this element
067:             * @param normal floating-point representation to be encoded
068:             */
069:            CompressionStreamNormal(CompressionStream stream, Vector3f normal) {
070:                this .normalX = normal.x;
071:                this .normalY = normal.y;
072:                this .normalZ = normal.z;
073:                stream.byteCount += 12;
074:            }
075:
076:            //
077:            // Normal Encoding Parameterization
078:            // 
079:            // A floating point normal is quantized to a desired number of bits by
080:            // comparing it to candidate entries in a table of every possible normal
081:            // at that quantization and finding the closest match.  This table of
082:            // normals is indexed by the following encoding:
083:            //
084:            // First, points on a unit radius sphere are parameterized by two angles,
085:            // th and psi, using usual spherical coordinates. th is the angle about
086:            // the y axis, psi is the inclination to the plane containing the point.
087:            // The mapping between rectangular and spherical coordinates is:
088:            // 
089:            // x = cos(th)*cos(psi)
090:            // y = sin(psi)
091:            // z = sin(th)*cos(psi)
092:            // 
093:            // Points on sphere are folded first by octant, and then by sort order
094:            // of xyz into one of six sextants. All the table encoding takes place in
095:            // the positive octant, in the region bounded by the half spaces:
096:            // 
097:            // x >= z
098:            // z >= y
099:            // y >= 0
100:            // 
101:            // This triangular shaped patch runs from 0 to 45 degrees in th, and
102:            // from 0 to as much as 0.615479709 (MAX_Y_ANG) in psi. The xyz bounds
103:            // of the patch is:
104:            // 
105:            // (1, 0, 0)  (1/sqrt(2), 0, 1/sqrt(2))  (1/sqrt(3), 1/sqrt(3), 1/sqrt(3))
106:            // 
107:            // When dicing this space up into discrete points, the choice for y is
108:            // linear quantization in psi.  This means that if the y range is to be
109:            // divided up into n segments, the angle of segment j is:
110:            // 
111:            // psi(j) = MAX_Y_ANG*(j/n)
112:            // 
113:            // The y height of the patch (in arc length) is *not* the same as the xz
114:            // dimension. However, the subdivision quantization needs to treat xz and
115:            // y equally. To achieve this, the th angles are re-parameterized as
116:            // reflected psi angles.  That is, the i-th point's th is:
117:            // 
118:            // th(i) = asin(tan(psi(i))) = asin(tan(MAX_Y_ANG*(i/n)))
119:            // 
120:            // To go the other direction, the angle th corresponds to the real index r
121:            // (in the same 0-n range as i):
122:            // 
123:            // r(th) = n*atan(sin(th))/MAX_Y_ANG
124:            // 
125:            // Rounded to the nearest integer, this gives the closest integer index i
126:            // to the xz angle th. Because the triangle has a straight edge on the
127:            // line x=z, it is more intuitive to index the xz angles in reverse
128:            // order.  Thus the two equations above are replaced by:
129:            // 
130:            // th(i) = asin(tan(psi(i))) = asin(tan(MAX_Y_ANG*((n-i)/n)))
131:            // 
132:            // r(th) = n*(1 - atan(sin(th))/MAX_Y_ANG)
133:            // 
134:            // Each level of quantization subdivides the triangular patch twice as
135:            // densely.  The case in which only the three vertices of the triangle are
136:            // present is the first logical stage of representation, but because of
137:            // how the table is encoded the first usable case starts one level of
138:            // sub-division later.  This three point level has an n of 2 by the above
139:            // conventions.
140:            //
141:            private static final int MAX_UV_BITS = 6;
142:            private static final int MAX_UV_ENTRIES = 64;
143:
144:            private static final double cgNormals[][][][] = new double[MAX_UV_BITS + 1][MAX_UV_ENTRIES + 1][MAX_UV_ENTRIES + 1][3];
145:
146:            private static final double MAX_Y_ANG = 0.615479709;
147:            private static final double UNITY_14 = 16384.0;
148:
149:            private static void computeNormals() {
150:                int inx, iny, inz, n;
151:                double th, psi, qnx, qny, qnz;
152:
153:                for (int quant = 0; quant <= MAX_UV_BITS; quant++) {
154:                    n = 1 << quant;
155:
156:                    for (int j = 0; j <= n; j++) {
157:                        for (int i = 0; i <= n; i++) {
158:                            if (i + j > n)
159:                                continue;
160:
161:                            psi = MAX_Y_ANG * (j / ((double) n));
162:                            th = Math.asin(Math.tan(MAX_Y_ANG
163:                                    * ((n - i) / ((double) n))));
164:
165:                            qnx = Math.cos(th) * Math.cos(psi);
166:                            qny = Math.sin(psi);
167:                            qnz = Math.sin(th) * Math.cos(psi);
168:
169:                            // The normal table uses 16-bit components and must be
170:                            // able to represent both +1.0 and -1.0, so convert the
171:                            // floating point normal components to fixed point with 14
172:                            // fractional bits, a unity bit, and a sign bit (s1.14).
173:                            // Set them back to get the float equivalent.
174:                            qnx = qnx * UNITY_14;
175:                            inx = (int) qnx;
176:                            qnx = inx;
177:                            qnx = qnx / UNITY_14;
178:
179:                            qny = qny * UNITY_14;
180:                            iny = (int) qny;
181:                            qny = iny;
182:                            qny = qny / UNITY_14;
183:
184:                            qnz = qnz * UNITY_14;
185:                            inz = (int) qnz;
186:                            qnz = inz;
187:                            qnz = qnz / UNITY_14;
188:
189:                            cgNormals[quant][j][i][0] = qnx;
190:                            cgNormals[quant][j][i][1] = qny;
191:                            cgNormals[quant][j][i][2] = qnz;
192:                        }
193:                    }
194:                }
195:            }
196:
197:            //
198:            // An inverse sine table is used for each quantization level to take the Y
199:            // component of a normal (which is the sine of the inclination angle) and
200:            // obtain the closest quantized Y angle.
201:            // 
202:            // At any level of compression, there are a fixed number of different Y
203:            // angles (between 0 and MAX_Y_ANG).  The inverse table is built to have
204:            // slightly more than twice as many entries as y angles at any particular
205:            // level; this ensures that the inverse look-up will get within one angle
206:            // of the right one.  The size of the table should be as small as
207:            // possible, but with its delta sine still smaller than the delta sine
208:            // between the last two angles to be encoded.
209:            // 
210:            // Example: the inverse sine table has a maximum angle of 0.615479709.  At
211:            // the maximum resolution of 6 bits there are 65 discrete angles used,
212:            // but twice as many are needed for thresholding between angles, so the
213:            // delta angle is 0.615479709/128. The difference then between the last
214:            // two angles to be encoded is:
215:            // sin(0.615479709*128.0/128.0) - sin(0.615479709*127.0/128.0) = 0.003932730
216:            // 
217:            // Using 8 significent bits below the binary point, fixed point can
218:            // represent sines in increments of 0.003906250, just slightly smaller.
219:            // However, because the maximum Y angle sine is 0.577350269, only 148
220:            // instead of 256 table entries are needed.
221:            // 
222:            private static final short inverseSine[][] = new short[MAX_UV_BITS + 1][];
223:
224:            // UNITY_14 * sin(MAX_Y_ANGLE)
225:            private static final short MAX_SIN_14BIT = 9459;
226:
227:            private static void computeInverseSineTables() {
228:                int intSin, deltaSin, intAngle;
229:                double floatSin, floatAngle;
230:                short sin14[] = new short[MAX_UV_ENTRIES + 1];
231:
232:                // Build table of sines in s1.14 fixed point for each of the
233:                // discrete angles used at maximum resolution.
234:                for (int i = 0; i <= MAX_UV_ENTRIES; i++) {
235:                    sin14[i] = (short) (UNITY_14 * Math.sin(i * MAX_Y_ANG
236:                            / MAX_UV_ENTRIES));
237:                }
238:
239:                for (int quant = 0; quant <= MAX_UV_BITS; quant++) {
240:                    switch (quant) {
241:                    default:
242:                    case 6:
243:                        // Delta angle: MAX_Y_ANGLE/128.0
244:                        // Bits below binary point for fixed point delta sine: 8
245:                        // Integer delta sine: 64
246:                        // Inverse sine table size: 148 entries
247:                        deltaSin = 1 << (14 - 8);
248:                        break;
249:                    case 5:
250:                        // Delta angle: MAX_Y_ANGLE/64.0
251:                        // Bits below binary point for fixed point delta sine: 7
252:                        // Integer delta sine: 128
253:                        // Inverse sine table size: 74 entries
254:                        deltaSin = 1 << (14 - 7);
255:                        break;
256:                    case 4:
257:                        // Delta angle: MAX_Y_ANGLE/32.0
258:                        // Bits below binary point for fixed point delta sine: 6
259:                        // Integer delta sine: 256
260:                        // Inverse sine table size: 37 entries
261:                        deltaSin = 1 << (14 - 6);
262:                        break;
263:                    case 3:
264:                        // Delta angle: MAX_Y_ANGLE/16.0
265:                        // Bits below binary point for fixed point delta sine: 5
266:                        // Integer delta sine: 512
267:                        // Inverse sine table size: 19 entries
268:                        deltaSin = 1 << (14 - 5);
269:                        break;
270:                    case 2:
271:                        // Delta angle: MAX_Y_ANGLE/8.0
272:                        // Bits below binary point for fixed point delta sine: 4
273:                        // Integer delta sine: 1024
274:                        // Inverse sine table size: 10 entries
275:                        deltaSin = 1 << (14 - 4);
276:                        break;
277:                    case 1:
278:                        // Delta angle: MAX_Y_ANGLE/4.0
279:                        // Bits below binary point for fixed point delta sine: 3
280:                        // Integer delta sine: 2048
281:                        // Inverse sine table size: 5 entries
282:                        deltaSin = 1 << (14 - 3);
283:                        break;
284:                    case 0:
285:                        // Delta angle: MAX_Y_ANGLE/2.0
286:                        // Bits below binary point for fixed point delta sine: 2
287:                        // Integer delta sine: 4096
288:                        // Inverse sine table size: 3 entries
289:                        deltaSin = 1 << (14 - 2);
290:                        break;
291:                    }
292:
293:                    inverseSine[quant] = new short[(MAX_SIN_14BIT / deltaSin) + 1];
294:
295:                    intSin = 0;
296:                    for (int i = 0; i < inverseSine[quant].length; i++) {
297:                        // Compute float representation of integer sine with desired
298:                        // number of fractional bits by effectively right shifting 14.
299:                        floatSin = intSin / UNITY_14;
300:
301:                        // Compute the angle with this sine value and quantize it.
302:                        floatAngle = Math.asin(floatSin);
303:                        intAngle = (int) ((floatAngle / MAX_Y_ANG) * (1 << quant));
304:
305:                        // Choose the closest of the three nearest quantized values
306:                        // intAngle-1, intAngle, and intAngle+1.
307:                        if (intAngle > 0) {
308:                            if (Math.abs(sin14[intAngle << (6 - quant)]
309:                                    - intSin) > Math
310:                                    .abs(sin14[(intAngle - 1) << (6 - quant)]
311:                                            - intSin))
312:                                intAngle = intAngle - 1;
313:                        }
314:
315:                        if (intAngle < (1 << quant)) {
316:                            if (Math.abs(sin14[intAngle << (6 - quant)]
317:                                    - intSin) > Math
318:                                    .abs(sin14[(intAngle + 1) << (6 - quant)]
319:                                            - intSin))
320:                                intAngle = intAngle + 1;
321:                        }
322:
323:                        inverseSine[quant][i] = (short) intAngle;
324:                        intSin += deltaSin;
325:                    }
326:                }
327:            }
328:
329:            /**
330:             * Compute static tables needed for normal quantization.
331:             */
332:            static {
333:                computeNormals();
334:                computeInverseSineTables();
335:            }
336:
337:            /**
338:             * Quantize the floating point normal to a 6-bit octant/sextant plus u,v
339:             * components of [0..6] bits.  Full resolution is 18 bits and the minimum
340:             * is 6 bits.
341:             *
342:             * @param stream CompressionStream associated with this element
343:             * @param table HuffmanTable for collecting data about the quantized
344:             * representation of this element
345:             */
346:            void quantize(CompressionStream stream, HuffmanTable huffmanTable) {
347:                double nx, ny, nz, t;
348:
349:                // Clamp UV quantization.
350:                int quant = (stream.normalQuant < 0 ? 0
351:                        : (stream.normalQuant > 6 ? 6 : stream.normalQuant));
352:
353:                nx = normalX;
354:                ny = normalY;
355:                nz = normalZ;
356:
357:                octant = 0;
358:                sextant = 0;
359:                u = 0;
360:                v = 0;
361:
362:                // Normalize the fixed point normal to the positive signed octant.
363:                if (nx < 0.0) {
364:                    octant |= 4;
365:                    nx = -nx;
366:                }
367:                if (ny < 0.0) {
368:                    octant |= 2;
369:                    ny = -ny;
370:                }
371:                if (nz < 0.0) {
372:                    octant |= 1;
373:                    nz = -nz;
374:                }
375:
376:                // Normalize the fixed point normal to the proper sextant of the octant.
377:                if (nx < ny) {
378:                    sextant |= 1;
379:                    t = nx;
380:                    nx = ny;
381:                    ny = t;
382:                }
383:                if (nz < ny) {
384:                    sextant |= 2;
385:                    t = ny;
386:                    ny = nz;
387:                    nz = t;
388:                }
389:                if (nx < nz) {
390:                    sextant |= 4;
391:                    t = nx;
392:                    nx = nz;
393:                    nz = t;
394:                }
395:
396:                // Convert the floating point y component to s1.14 fixed point.
397:                int yInt = (int) (ny * UNITY_14);
398:
399:                // The y component of the normal is the sine of the y angle.  Quantize
400:                // the y angle by using the fixed point y component as an index into
401:                // the inverse sine table of the correct size for the quantization
402:                // level.  (12 - quant) bits of the s1.14 y normal component are
403:                // rolled off with a right shift; the remaining bits then match the
404:                // number of bits used to represent the delta sine of the table.
405:                int yIndex = inverseSine[quant][yInt >> (12 - quant)];
406:
407:                // Search the two xz rows near y for the best match.
408:                int ii = 0;
409:                int jj = 0;
410:                int n = 1 << quant;
411:                double dot, bestDot = -1;
412:
413:                for (int j = yIndex - 1; j < yIndex + 1 && j <= n; j++) {
414:                    if (j < 0)
415:                        continue;
416:
417:                    for (int i = 0; i <= n; i++) {
418:                        if (i + j > n)
419:                            continue;
420:
421:                        dot = nx * cgNormals[quant][j][i][0] + ny
422:                                * cgNormals[quant][j][i][1] + nz
423:                                * cgNormals[quant][j][i][2];
424:
425:                        if (dot > bestDot) {
426:                            bestDot = dot;
427:                            ii = i;
428:                            jj = j;
429:                        }
430:                    }
431:                }
432:
433:                // Convert u and v to standard grid form.
434:                u = ii << (6 - quant);
435:                v = jj << (6 - quant);
436:
437:                // Check for special normals and specially encode them.
438:                specialNormal = false;
439:                if (u == 64 && v == 0) {
440:                    // six coordinate axes case
441:                    if (sextant == 0 || sextant == 2) {
442:                        // +/- x-axis
443:                        specialSextant = 0x6;
444:                        specialOctant = ((octant & 4) != 0) ? 0x2 : 0;
445:
446:                    } else if (sextant == 3 || sextant == 1) {
447:                        // +/- y-axis
448:                        specialSextant = 0x6;
449:                        specialOctant = 4 | (((octant & 2) != 0) ? 0x2 : 0);
450:
451:                    } else if (sextant == 5 || sextant == 4) {
452:                        // +/- z-axis
453:                        specialSextant = 0x7;
454:                        specialOctant = ((octant & 1) != 0) ? 0x2 : 0;
455:                    }
456:                    specialNormal = true;
457:                    u = v = 0;
458:
459:                } else if (u == 0 && v == 64) {
460:                    // eight mid point case
461:                    specialSextant = 6 | (octant >> 2);
462:                    specialOctant = ((octant & 0x3) << 1) | 1;
463:                    specialNormal = true;
464:                    u = v = 0;
465:                }
466:
467:                // Compute deltas if possible.
468:                // Use the non-normalized ii and jj indices.
469:                int du = 0;
470:                int dv = 0;
471:                int uv64 = 64 >> (6 - quant);
472:
473:                absolute = false;
474:                if (stream.firstNormal || stream.normalQuantChanged
475:                        || stream.lastSpecialNormal || specialNormal) {
476:                    // The first normal by definition is absolute, and normals cannot
477:                    // be represented as deltas to or from special normals, nor from
478:                    // normals with a different quantization.
479:                    absolute = true;
480:                    stream.firstNormal = false;
481:                    stream.normalQuantChanged = false;
482:
483:                } else if (stream.lastOctant == octant
484:                        && stream.lastSextant == sextant) {
485:                    // Deltas are always allowed within the same sextant/octant.
486:                    du = ii - stream.lastU;
487:                    dv = jj - stream.lastV;
488:
489:                } else if (stream.lastOctant != octant
490:                        && stream.lastSextant == sextant
491:                        && (((sextant == 1 || sextant == 5) && (stream.lastOctant & 3) == (octant & 3))
492:                                || ((sextant == 0 || sextant == 4) && (stream.lastOctant & 5) == (octant & 5)) || ((sextant == 2 || sextant == 3) && (stream.lastOctant & 6) == (octant & 6)))) {
493:                    // If the sextants are the same, the octants can differ only when
494:                    // they are bordering each other on the same edge that the
495:                    // sextant has.
496:                    du = ii - stream.lastU;
497:                    dv = -jj - stream.lastV;
498:
499:                    // Can't delta by less than -64.
500:                    if (dv < -uv64)
501:                        absolute = true;
502:
503:                    // Can't delta doubly defined points.
504:                    if (jj == 0)
505:                        absolute = true;
506:
507:                } else if (stream.lastOctant == octant
508:                        && stream.lastSextant != sextant
509:                        && ((sextant == 0 && stream.lastSextant == 4)
510:                                || (sextant == 4 && stream.lastSextant == 0)
511:                                || (sextant == 1 && stream.lastSextant == 5)
512:                                || (sextant == 5 && stream.lastSextant == 1)
513:                                || (sextant == 2 && stream.lastSextant == 3) || (sextant == 3 && stream.lastSextant == 2))) {
514:                    // If the octants are the same, the sextants must border on
515:                    // the i side (this case) or the j side (next case).
516:                    du = -ii - stream.lastU;
517:                    dv = jj - stream.lastV;
518:
519:                    // Can't delta by less than -64.
520:                    if (du < -uv64)
521:                        absolute = true;
522:
523:                    // Can't delta doubly defined points.
524:                    if (ii == 0)
525:                        absolute = true;
526:
527:                } else if (stream.lastOctant == octant
528:                        && stream.lastSextant != sextant
529:                        && ((sextant == 0 && stream.lastSextant == 2)
530:                                || (sextant == 2 && stream.lastSextant == 0)
531:                                || (sextant == 1 && stream.lastSextant == 3)
532:                                || (sextant == 3 && stream.lastSextant == 1)
533:                                || (sextant == 4 && stream.lastSextant == 5) || (sextant == 5 && stream.lastSextant == 4))) {
534:                    // If the octants are the same, the sextants must border on
535:                    // the j side (this case) or the i side (previous case).
536:                    if (((ii + jj) != uv64) && (ii != 0) && (jj != 0)) {
537:                        du = uv64 - ii - stream.lastU;
538:                        dv = uv64 - jj - stream.lastV;
539:
540:                        // Can't delta by greater than +63.
541:                        if ((du >= uv64) || (dv >= uv64))
542:                            absolute = true;
543:                    } else
544:                        // Can't delta doubly defined points.
545:                        absolute = true;
546:
547:                } else
548:                    // Can't delta this normal.
549:                    absolute = true;
550:
551:                if (absolute == false) {
552:                    // Convert du and dv to standard grid form.
553:                    u = du << (6 - quant);
554:                    v = dv << (6 - quant);
555:                }
556:
557:                // Compute length and shift common to all components.
558:                computeLengthShift(u, v);
559:
560:                if (absolute && length > 6) {
561:                    // Absolute normal u, v components are unsigned 6-bit integers, so
562:                    // truncate the 0 sign bit for values > 0x001f.
563:                    length = 6;
564:                }
565:
566:                // Add this element to the Huffman table associated with this stream.
567:                huffmanTable.addNormalEntry(length, shift, absolute);
568:
569:                // Save current normal as last.
570:                stream.lastSextant = sextant;
571:                stream.lastOctant = octant;
572:                stream.lastU = ii;
573:                stream.lastV = jj;
574:                stream.lastSpecialNormal = specialNormal;
575:
576:                // Copy and retain absolute normal for mesh buffer lookup.
577:                uAbsolute = ii;
578:                vAbsolute = jj;
579:            }
580:
581:            /**
582:             * Output a setNormal command.
583:             *
584:             * @param table HuffmanTable mapping quantized representations to
585:             * compressed encodings
586:             * @param output CommandStream for collecting compressed output
587:             */
588:            void outputCommand(HuffmanTable table, CommandStream output) {
589:                outputNormal(table, output, CommandStream.SET_NORM, 8);
590:            }
591:
592:            /**
593:             * Output a normal subcommand.
594:             *
595:             * @param table HuffmanTable mapping quantized representations to
596:             * compressed encodings
597:             * @param output CommandStream for collecting compressed output
598:             */
599:            void outputSubcommand(HuffmanTable table, CommandStream output) {
600:                outputNormal(table, output, 0, 6);
601:            }
602:
603:            //
604:            // Output the final compressed bits to the output command stream.
605:            //
606:            private void outputNormal(HuffmanTable table, CommandStream output,
607:                    int header, int headerLength) {
608:
609:                HuffmanNode t;
610:
611:                // Look up the Huffman token for this compression stream element.
612:                t = table.getNormalEntry(length, shift, absolute);
613:
614:                // Construct the normal subcommand.
615:                int componentLength = t.dataLength - t.shift;
616:                int subcommandLength = 0;
617:                long normalSubcommand = 0;
618:
619:                if (absolute) {
620:                    // A 3-bit sextant and a 3-bit octant are always present.
621:                    subcommandLength = t.tagLength + 6;
622:
623:                    if (specialNormal)
624:                        // Use the specially-encoded sextant and octant.
625:                        normalSubcommand = (t.tag << 6) | (specialSextant << 3)
626:                                | specialOctant;
627:                    else
628:                        // Use the general encoding rule.
629:                        normalSubcommand = (t.tag << 6) | (sextant << 3)
630:                                | octant;
631:                } else {
632:                    // The tag is immediately followed by the u and v delta components.
633:                    subcommandLength = t.tagLength;
634:                    normalSubcommand = t.tag;
635:                }
636:
637:                // Add the u and v values to the subcommand.
638:                subcommandLength += (2 * componentLength);
639:
640:                u = (u >> t.shift) & (int) lengthMask[componentLength];
641:                v = (v >> t.shift) & (int) lengthMask[componentLength];
642:
643:                normalSubcommand = (normalSubcommand << (2 * componentLength))
644:                        | (u << (1 * componentLength))
645:                        | (v << (0 * componentLength));
646:
647:                if (subcommandLength < 6) {
648:                    // The header will have some empty bits. The Huffman tag
649:                    // computation will prevent this if necessary.
650:                    header |= (int) (normalSubcommand << (6 - subcommandLength));
651:                    subcommandLength = 0;
652:                } else {
653:                    // Move the 1st 6 bits of the subcommand into the header.
654:                    header |= (int) (normalSubcommand >>> (subcommandLength - 6));
655:                    subcommandLength -= 6;
656:                }
657:
658:                // Add the header and body to the output buffer.
659:                output.addCommand(header, headerLength, normalSubcommand,
660:                        subcommandLength);
661:            }
662:
663:            public String toString() {
664:                String fixed;
665:
666:                if (specialNormal)
667:                    fixed = " special normal, sextant " + specialSextant
668:                            + " octant " + specialOctant;
669:
670:                else if (absolute)
671:                    fixed = " sextant " + sextant + " octant " + octant + " u "
672:                            + u + " v " + v;
673:                else
674:                    fixed = " du " + u + " dv " + v;
675:
676:                return "normal: " + normalX + " " + normalY + " " + normalZ
677:                        + "\n" + fixed + "\n" + " length " + length + " shift "
678:                        + shift + (absolute ? " absolute" : " relative");
679:            }
680:        }
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