aboutsummaryrefslogtreecommitdiffstatshomepage
path: root/OpenSim/Region/Physics/BulletSPlugin/BSLinksetCompound.cs
blob: 36bae9bba4d2c70a31ddde0fa85ebb12aeb70c1f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
/*
 * Copyright (c) Contributors, http://opensimulator.org/
 * See CONTRIBUTORS.TXT for a full list of copyright holders.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyrightD
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the OpenSimulator Project nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
using System;
using System.Collections.Generic;
using System.Text;

using OpenSim.Framework;

using OMV = OpenMetaverse;

namespace OpenSim.Region.Physics.BulletSPlugin
{

// When a child is linked, the relationship position of the child to the parent
//    is remembered so the child's world position can be recomputed when it is
//    removed from the linkset.
sealed class BSLinksetCompoundInfo : BSLinksetInfo
{
    public int Index;
    public OMV.Vector3 OffsetFromRoot;
    public OMV.Vector3 OffsetFromCenterOfMass;
    public OMV.Quaternion OffsetRot;
    public BSLinksetCompoundInfo(int indx, OMV.Vector3 p, OMV.Quaternion r)
    {
        Index = indx;
        OffsetFromRoot = p;
        OffsetFromCenterOfMass = p;
        OffsetRot = r;
    }
    // 'centerDisplacement' is the distance from the root the the center-of-mass (Bullet 'zero' of the shape)
    public BSLinksetCompoundInfo(int indx, BSPrimLinkable root, BSPrimLinkable child, OMV.Vector3 centerDisplacement)
    {
        // Each child position and rotation is given relative to the center-of-mass.
        OMV.Quaternion invRootOrientation = OMV.Quaternion.Inverse(root.RawOrientation);
        OMV.Vector3 displacementFromRoot = (child.RawPosition - root.RawPosition) * invRootOrientation;
        OMV.Vector3 displacementFromCOM = displacementFromRoot - centerDisplacement;
        OMV.Quaternion displacementRot = child.RawOrientation * invRootOrientation;

        // Save relative position for recomputing child's world position after moving linkset.
        Index = indx;
        OffsetFromRoot = displacementFromRoot;
        OffsetFromCenterOfMass = displacementFromCOM;
        OffsetRot = displacementRot;
    }
    public override void Clear()
    {
        Index = 0;
        OffsetFromRoot = OMV.Vector3.Zero;
        OffsetFromCenterOfMass = OMV.Vector3.Zero;
        OffsetRot = OMV.Quaternion.Identity;
    }
    public override string ToString()
    {
        StringBuilder buff = new StringBuilder();
        buff.Append("<i=");
        buff.Append(Index.ToString());
        buff.Append(",p=");
        buff.Append(OffsetFromRoot.ToString());
        buff.Append(",m=");
        buff.Append(OffsetFromCenterOfMass.ToString());
        buff.Append(",r=");
        buff.Append(OffsetRot.ToString());
        buff.Append(">");
        return buff.ToString();
    }
};

public sealed class BSLinksetCompound : BSLinkset
{
    private static string LogHeader = "[BULLETSIM LINKSET COMPOUND]";

    public BSLinksetCompound(BSScene scene, BSPrimLinkable parent) : base(scene, parent)
    {
    }

    // For compound implimented linksets, if there are children, use compound shape for the root.
    public override BSPhysicsShapeType PreferredPhysicalShape(BSPrimLinkable requestor)
    { 
        // Returning 'unknown' means we don't have a preference.
        BSPhysicsShapeType ret = BSPhysicsShapeType.SHAPE_UNKNOWN;
        if (IsRoot(requestor) && HasAnyChildren)
        {
            ret = BSPhysicsShapeType.SHAPE_COMPOUND;
        }
        // DetailLog("{0},BSLinksetCompound.PreferredPhysicalShape,call,shape={1}", LinksetRoot.LocalID, ret);
        return ret;
    }

    // When physical properties are changed the linkset needs to recalculate
    //   its internal properties.
    public override void Refresh(BSPrimLinkable requestor)
    {
        base.Refresh(requestor);

        // Something changed so do the rebuilding thing
        // ScheduleRebuild();
    }

    // Schedule a refresh to happen after all the other taint processing.
    private void ScheduleRebuild(BSPrimLinkable requestor)
    {
        DetailLog("{0},BSLinksetCompound.ScheduleRebuild,,rebuilding={1},hasChildren={2},actuallyScheduling={3}", 
                            requestor.LocalID, Rebuilding, HasAnyChildren, (!Rebuilding && HasAnyChildren));
        // When rebuilding, it is possible to set properties that would normally require a rebuild.
        //    If already rebuilding, don't request another rebuild.
        //    If a linkset with just a root prim (simple non-linked prim) don't bother rebuilding.
        if (!Rebuilding && HasAnyChildren)
        {
            PhysicsScene.PostTaintObject("BSLinksetCompound.ScheduleRebuild", LinksetRoot.LocalID, delegate()
            {
                if (HasAnyChildren)
                    RecomputeLinksetCompound();
            });
        }
    }

    // The object is going dynamic (physical). Do any setup necessary for a dynamic linkset.
    // Only the state of the passed object can be modified. The rest of the linkset
    //     has not yet been fully constructed.
    // Return 'true' if any properties updated on the passed object.
    // Called at taint-time!
    public override bool MakeDynamic(BSPrimLinkable child)
    {
        bool ret = false;
        DetailLog("{0},BSLinksetCompound.MakeDynamic,call,IsRoot={1}", child.LocalID, IsRoot(child));
        if (IsRoot(child))
        {
            // The root is going dynamic. Rebuild the linkset so parts and mass get computed properly.
            ScheduleRebuild(LinksetRoot);
        }
        else
        {
            // The origional prims are removed from the world as the shape of the root compound
            //     shape takes over.
            PhysicsScene.PE.AddToCollisionFlags(child.PhysBody, CollisionFlags.CF_NO_CONTACT_RESPONSE);
            PhysicsScene.PE.ForceActivationState(child.PhysBody, ActivationState.DISABLE_SIMULATION);
            // We don't want collisions from the old linkset children.
            PhysicsScene.PE.RemoveFromCollisionFlags(child.PhysBody, CollisionFlags.BS_SUBSCRIBE_COLLISION_EVENTS);

            child.PhysBody.collisionType = CollisionType.LinksetChild;

            ret = true;
        }
        return ret;
    }

    // The object is going static (non-physical). Do any setup necessary for a static linkset.
    // Return 'true' if any properties updated on the passed object.
    // This doesn't normally happen -- OpenSim removes the objects from the physical
    //     world if it is a static linkset.
    // Called at taint-time!
    public override bool MakeStatic(BSPrimLinkable child)
    {
        bool ret = false;
        DetailLog("{0},BSLinksetCompound.MakeStatic,call,IsRoot={1}", child.LocalID, IsRoot(child));
        if (IsRoot(child))
        {
            ScheduleRebuild(LinksetRoot);
        }
        else
        {
            // The non-physical children can come back to life.
            PhysicsScene.PE.RemoveFromCollisionFlags(child.PhysBody, CollisionFlags.CF_NO_CONTACT_RESPONSE);

            child.PhysBody.collisionType = CollisionType.LinksetChild;

            // Don't force activation so setting of DISABLE_SIMULATION can stay if used.
            PhysicsScene.PE.Activate(child.PhysBody, false);
            ret = true;
        }
        return ret;
    }

    // 'physicalUpdate' is true if these changes came directly from the physics engine. Don't need to rebuild then.
    // Called at taint-time.
    public override void UpdateProperties(UpdatedProperties whichUpdated, BSPrimLinkable updated)
    {
        // The user moving a child around requires the rebuilding of the linkset compound shape
        // One problem is this happens when a border is crossed -- the simulator implementation
        //    stores the position into the group which causes the move of the object
        //    but it also means all the child positions get updated.
        //    What would cause an unnecessary rebuild so we make sure the linkset is in a
        //    region before bothering to do a rebuild.
        if (!IsRoot(updated) && PhysicsScene.TerrainManager.IsWithinKnownTerrain(LinksetRoot.RawPosition))
        {
            // If a child of the linkset is updating only the position or rotation, that can be done
            //    without rebuilding the linkset.
            // If a handle for the child can be fetch, we update the child here. If a rebuild was
            //    scheduled by someone else, the rebuild will just replace this setting.

            bool updatedChild = false;
            // Anything other than updating position or orientation usually means a physical update
            //     and that is caused by us updating the object.
            if ((whichUpdated & ~(UpdatedProperties.Position | UpdatedProperties.Orientation)) == 0)
            {
                // Gather the child info. It might not be there if the linkset is in transition.
                BSLinksetCompoundInfo lsi = updated.LinksetInfo as BSLinksetCompoundInfo;
                if (lsi != null)
                {
                    // Since the child moved or rotationed, it needs a new relative position within the linkset
                    BSLinksetCompoundInfo newLsi = new BSLinksetCompoundInfo(lsi.Index, LinksetRoot, updated, OMV.Vector3.Zero);
                    updated.LinksetInfo = newLsi;

                    // Find the physical instance of the child 
                    if (LinksetRoot.PhysShape.HasPhysicalShape && PhysicsScene.PE.IsCompound(LinksetRoot.PhysShape))
                    {
                        // It is possible that the linkset is still under construction and the child is not yet
                        //    inserted into the compound shape. A rebuild of the linkset in a pre-step action will
                        //    build the whole thing with the new position or rotation.
                        // The index must be checked because Bullet references the child array but does no validity
                        //    checking of the child index passed.
                        int numLinksetChildren = PhysicsScene.PE.GetNumberOfCompoundChildren(LinksetRoot.PhysShape);
                        if (lsi.Index < numLinksetChildren)
                        {
                            BulletShape linksetChildShape = PhysicsScene.PE.GetChildShapeFromCompoundShapeIndex(LinksetRoot.PhysShape, lsi.Index);
                            if (linksetChildShape.HasPhysicalShape)
                            {
                                // Found the child shape within the compound shape
                                PhysicsScene.PE.UpdateChildTransform(LinksetRoot.PhysShape, lsi.Index,
                                                                            newLsi.OffsetFromCenterOfMass,
                                                                            newLsi.OffsetRot,
                                                                            true /* shouldRecalculateLocalAabb */);
                                updatedChild = true;
                                DetailLog("{0},BSLinksetCompound.UpdateProperties,changeChildPosRot,whichUpdated={1},newLsi={2}",
                                                                            updated.LocalID, whichUpdated, newLsi);
                            }
                            else    // DEBUG DEBUG
                            {       // DEBUG DEBUG
                                DetailLog("{0},BSLinksetCompound.UpdateProperties,couldNotUpdateChild,noChildShape,shape={1}",
                                                                            updated.LocalID, linksetChildShape);
                            }       // DEBUG DEBUG
                        }
                        else    // DEBUG DEBUG
                        {       // DEBUG DEBUG
                            // the child is not yet in the compound shape. This is non-fatal.
                            DetailLog("{0},BSLinksetCompound.UpdateProperties,couldNotUpdateChild,childNotInCompoundShape,numChildren={1},index={2}",
                                                                        updated.LocalID, numLinksetChildren, lsi.Index);
                        }       // DEBUG DEBUG
                    }
                    else    // DEBUG DEBUG
                    {       // DEBUG DEBUG
                        DetailLog("{0},BSLinksetCompound.UpdateProperties,couldNotUpdateChild,noBodyOrNotCompound", updated.LocalID);
                    }       // DEBUG DEBUG
                }
                else    // DEBUG DEBUG
                {       // DEBUG DEBUG
                    DetailLog("{0},BSLinksetCompound.UpdateProperties,couldNotUpdateChild,noLinkSetInfo,rootPhysShape={1}",
                                                    updated.LocalID, LinksetRoot.PhysShape);
                }       // DEBUG DEBUG

                if (!updatedChild)
                {
                    // If couldn't do the individual child, the linkset needs a rebuild to incorporate the new child info.
                    // Note: there are several ways through this code that will not update the child if
                    //    the linkset is being rebuilt. In this case, scheduling a rebuild is a NOOP since
                    //    there will already be a rebuild scheduled.
                    DetailLog("{0},BSLinksetCompound.UpdateProperties,couldNotUpdateChild.schedulingRebuild,whichUpdated={1}",
                                                                    updated.LocalID, whichUpdated);
                    updated.LinksetInfo = null; // setting to 'null' causes relative position to be recomputed.
                    ScheduleRebuild(updated);
                }
            }
        }
    }

    // Routine called when rebuilding the body of some member of the linkset.
    // Since we don't keep in world relationships, do nothing unless it's a child changing.
    // Returns 'true' of something was actually removed and would need restoring
    // Called at taint-time!!
    public override bool RemoveBodyDependencies(BSPrimLinkable child)
    {
        bool ret = false;

        DetailLog("{0},BSLinksetCompound.RemoveBodyDependencies,refreshIfChild,rID={1},rBody={2},isRoot={3}",
                        child.LocalID, LinksetRoot.LocalID, LinksetRoot.PhysBody, IsRoot(child));

        if (!IsRoot(child))
        {
            // Because it is a convenient time, recompute child world position and rotation based on
            //    its position in the linkset.
            RecomputeChildWorldPosition(child, true /* inTaintTime */);
            child.LinksetInfo = null;
        }

        // Cannot schedule a refresh/rebuild here because this routine is called when
        //     the linkset is being rebuilt.
        // InternalRefresh(LinksetRoot);

        return ret;
    }

    // When the linkset is built, the child shape is added to the compound shape relative to the
    //    root shape. The linkset then moves around but this does not move the actual child
    //    prim. The child prim's location must be recomputed based on the location of the root shape.
    private void RecomputeChildWorldPosition(BSPrimLinkable child, bool inTaintTime)
    {
        // For the moment (20130201), disable this computation (converting the child physical addr back to
        //    a region address) until we have a good handle on center-of-mass offsets and what the physics
        //    engine moving a child actually means.
        // The simulator keeps track of where children should be as the linkset moves. Setting
        //    the pos/rot here does not effect that knowledge as there is no good way for the
        //    physics engine to send the simulator an update for a child.

        /*
        BSLinksetCompoundInfo lci = child.LinksetInfo as BSLinksetCompoundInfo;
        if (lci != null)
        {
            if (inTaintTime)
            {
                OMV.Vector3 oldPos = child.RawPosition;
                child.ForcePosition = LinksetRoot.RawPosition + lci.OffsetFromRoot;
                child.ForceOrientation = LinksetRoot.RawOrientation * lci.OffsetRot;
                DetailLog("{0},BSLinksetCompound.RecomputeChildWorldPosition,oldPos={1},lci={2},newPos={3}",
                                            child.LocalID, oldPos, lci, child.RawPosition);
            }
            else
            {
                // TaintedObject is not used here so the raw position is set now and not at taint-time.
                child.Position = LinksetRoot.RawPosition + lci.OffsetFromRoot;
                child.Orientation = LinksetRoot.RawOrientation * lci.OffsetRot;
            }
        }
        else
        {
            // This happens when children have been added to the linkset but the linkset
            //     has not been constructed yet. So like, at taint time, adding children to a linkset
            //     and then changing properties of the children (makePhysical, for instance)
            //     but the post-print action of actually rebuilding the linkset has not yet happened.
            // PhysicsScene.Logger.WarnFormat("{0} Restoring linkset child position failed because of no relative position computed. ID={1}",
            //                                 LogHeader, child.LocalID);
            DetailLog("{0},BSLinksetCompound.recomputeChildWorldPosition,noRelativePositonInfo", child.LocalID);
        }
        */
    }

    // ================================================================

    // Add a new child to the linkset.
    // Called while LinkActivity is locked.
    protected override void AddChildToLinkset(BSPrimLinkable child)
    {
        if (!HasChild(child))
        {
            m_children.Add(child);

            DetailLog("{0},BSLinksetCompound.AddChildToLinkset,call,child={1}", LinksetRoot.LocalID, child.LocalID);

            // Rebuild the compound shape with the new child shape included
            ScheduleRebuild(child);
        }
        return;
    }

    // Remove the specified child from the linkset.
    // Safe to call even if the child is not really in the linkset.
    protected override void RemoveChildFromLinkset(BSPrimLinkable child)
    {
        if (m_children.Remove(child))
        {
            DetailLog("{0},BSLinksetCompound.RemoveChildFromLinkset,call,rID={1},rBody={2},cID={3},cBody={4}",
                            child.LocalID,
                            LinksetRoot.LocalID, LinksetRoot.PhysBody.AddrString,
                            child.LocalID, child.PhysBody.AddrString);

            // Cause the child's body to be rebuilt and thus restored to normal operation
            RecomputeChildWorldPosition(child, false);
            child.LinksetInfo = null;
            child.ForceBodyShapeRebuild(false);

            if (!HasAnyChildren)
            {
                // The linkset is now empty. The root needs rebuilding.
                LinksetRoot.ForceBodyShapeRebuild(false);
            }
            else
            {
                // Rebuild the compound shape with the child removed
                ScheduleRebuild(LinksetRoot);
            }
        }
        return;
    }

    // Called before the simulation step to make sure the compound based linkset
    //    is all initialized.
    // Constraint linksets are rebuilt every time.
    // Note that this works for rebuilding just the root after a linkset is taken apart.
    // Called at taint time!!
    private bool disableCOM = true;     // DEBUG DEBUG: disable until we get this debugged
    private void RecomputeLinksetCompound()
    {
        try
        {
            // Suppress rebuilding while rebuilding. (We know rebuilding is on only one thread.)
            Rebuilding = true;

            // Cause the root shape to be rebuilt as a compound object with just the root in it
            LinksetRoot.ForceBodyShapeRebuild(true /* inTaintTime */);

            // The center of mass for the linkset is the geometric center of the group.
            // Compute a displacement for each component so it is relative to the center-of-mass.
            // Bullet presumes an object's origin (relative <0,0,0>) is its center-of-mass
            OMV.Vector3 centerOfMass;
            OMV.Vector3 centerDisplacement = OMV.Vector3.Zero;
            if (disableCOM)                             // DEBUG DEBUG
            {                                           // DEBUG DEBUG
                centerOfMass = LinksetRoot.RawPosition; // DEBUG DEBUG
                // LinksetRoot.PositionDisplacement = OMV.Vector3.Zero;
            }                                           // DEBUG DEBUG
            else
            {
                centerOfMass = ComputeLinksetCenterOfMass();
                // 'centerDisplacement' is the value to *add* to all the shape offsets
                centerDisplacement = LinksetRoot.RawPosition - centerOfMass;

                // Since we're displacing the center of the shape, we need to move the body in the world
                // LinksetRoot.PositionDisplacement = centerDisplacement;

                // This causes the root prim position to be set properly based on the new PositionDisplacement
                LinksetRoot.ForcePosition = LinksetRoot.RawPosition;
                // Update the local transform for the root child shape so it is offset from the <0,0,0> which is COM
                PhysicsScene.PE.UpdateChildTransform(LinksetRoot.PhysShape, 0, -centerDisplacement, OMV.Quaternion.Identity, false);
                DetailLog("{0},BSLinksetCompound.RecomputeLinksetCompound,COM,com={1},rootPos={2},centerDisp={3}",
                                        LinksetRoot.LocalID, centerOfMass, LinksetRoot.RawPosition, centerDisplacement);
            }

            DetailLog("{0},BSLinksetCompound.RecomputeLinksetCompound,start,rBody={1},rShape={2},numChildren={3}",
                            LinksetRoot.LocalID, LinksetRoot.PhysBody, LinksetRoot.PhysShape, NumberOfChildren);

            // Add a shape for each of the other children in the linkset
            int memberIndex = 1;
            ForEachMember(delegate(BSPrimLinkable cPrim)
            {
                if (!IsRoot(cPrim))
                {
                    // Compute the displacement of the child from the root of the linkset.
                    // This info is saved in the child prim so the relationship does not
                    //    change over time and the new child position can be computed
                    //    when the linkset is being disassembled (the linkset may have moved).
                    BSLinksetCompoundInfo lci = cPrim.LinksetInfo as BSLinksetCompoundInfo;
                    if (lci == null)
                    {
                        lci = new BSLinksetCompoundInfo(memberIndex, LinksetRoot, cPrim, centerDisplacement);
                        cPrim.LinksetInfo = lci;
                        DetailLog("{0},BSLinksetCompound.RecomputeLinksetCompound,creatingRelPos,lci={1}", cPrim.LocalID, lci);
                    }

                    DetailLog("{0},BSLinksetCompound.RecomputeLinksetCompound,addMemberToShape,mID={1},mShape={2},lci={3}",
                                                LinksetRoot.LocalID, cPrim.LocalID, cPrim.PhysShape, lci);

                    if (cPrim.PhysShape.isNativeShape)
                    {
                        // A native shape is turned into a hull collision shape because native
                        //    shapes are not shared so we have to hullify it so it will be tracked
                        //    and freed at the correct time. This also solves the scaling problem
                        //    (native shapes scaled but hull/meshes are assumed to not be).
                        // TODO: decide of the native shape can just be used in the compound shape.
                        //    Use call to CreateGeomNonSpecial().
                        BulletShape saveShape = cPrim.PhysShape;
                        cPrim.PhysShape.Clear();        // Don't let the create free the child's shape
                        // PhysicsScene.Shapes.CreateGeomNonSpecial(true, cPrim, null);
                        PhysicsScene.Shapes.CreateGeomMeshOrHull(cPrim, null);
                        BulletShape newShape = cPrim.PhysShape;
                        cPrim.PhysShape = saveShape;
                        PhysicsScene.PE.AddChildShapeToCompoundShape(LinksetRoot.PhysShape, newShape, lci.OffsetFromCenterOfMass, lci.OffsetRot);
                    }
                    else
                    {
                        // For the shared shapes (meshes and hulls), just use the shape in the child.
                        // The reference count added here will be decremented when the compound shape
                        //     is destroyed in BSShapeCollection (the child shapes are looped over and dereferenced).
                        if (PhysicsScene.Shapes.ReferenceShape(cPrim.PhysShape))
                        {
                            PhysicsScene.Logger.ErrorFormat("{0} Rebuilt sharable shape when building linkset! Region={1}, primID={2}, shape={3}",
                                                LogHeader, PhysicsScene.RegionName, cPrim.LocalID, cPrim.PhysShape);
                        }
                        PhysicsScene.PE.AddChildShapeToCompoundShape(LinksetRoot.PhysShape, cPrim.PhysShape, lci.OffsetFromCenterOfMass, lci.OffsetRot);
                    }
                    lci.Index = memberIndex;
                    memberIndex++;
                }
                return false;   // 'false' says to move onto the next child in the list
            });

            // With all of the linkset packed into the root prim, it has the mass of everyone.
            LinksetMass = ComputeLinksetMass();
            LinksetRoot.UpdatePhysicalMassProperties(LinksetMass, true);
        }
        finally
        {
            Rebuilding = false;
        }

        PhysicsScene.PE.RecalculateCompoundShapeLocalAabb(LinksetRoot.PhysShape);
    }
}
}