opensim/OpenSim/Region/PhysicsModules/BulletS/BSActorLockAxis.cs

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using OMV = OpenMetaverse;

namespace OpenSim.Region.PhysicsModule.BulletS
{
public class BSActorLockAxis : BSActor
{
    private BSConstraint LockAxisConstraint = null;
    private bool HaveRegisteredForBeforeStepCallback = false;

    // The lock access flags (which axises were locked) when the contraint was built.
    // Used to see if locking has changed since when the constraint was built.
    OMV.Vector3 LockAxisLinearFlags;
    OMV.Vector3 LockAxisAngularFlags;

    public BSActorLockAxis(BSScene physicsScene, BSPhysObject pObj, string actorName)
        : base(physicsScene, pObj, actorName)
    {
        m_physicsScene.DetailLog("{0},BSActorLockAxis,constructor", m_controllingPrim.LocalID);
        LockAxisConstraint = null;
        HaveRegisteredForBeforeStepCallback = false;
    }

    // BSActor.isActive
    public override bool isActive
    {
        get { return Enabled && m_controllingPrim.IsPhysicallyActive; }
    }

    // Release any connections and resources used by the actor.
    // BSActor.Dispose()
    public override void Dispose()
    {
        Enabled = false;
        UnRegisterForBeforeStepCallback();
        RemoveAxisLockConstraint();
    }

    // Called when physical parameters (properties set in Bullet) need to be re-applied.
    // Called at taint-time.
    // BSActor.Refresh()
    public override void Refresh()
    {
        // Since the axis logging is done with a constraint, Refresh() time is good for
        //    changing parameters but this needs to wait until the prim/linkset is physically
        //    constructed. Therefore, the constraint itself is placed at pre-step time.

        // If all the axis are free, we don't need to exist
        // Refresh() only turns off. Enabling is done by InitializeAxisActor()
        //      whenever parameters are changed.
        //      This leaves 'enable' free to turn off an actor when it is not wanted to run.
        if (m_controllingPrim.LockedAngularAxis == m_controllingPrim.LockedAxisFree
                && m_controllingPrim.LockedLinearAxis == m_controllingPrim.LockedAxisFree)
        {
            Enabled = false;
        }

        if (isActive)
        {
            RegisterForBeforeStepCallback();
        }
        else
        {
            RemoveDependencies();
            UnRegisterForBeforeStepCallback();
        }
    }

    // The object's physical representation is being rebuilt so pick up any physical dependencies (constraints, ...).
    //     Register a prestep action to restore physical requirements before the next simulation step.
    // Called at taint-time.
    // BSActor.RemoveDependencies()
    public override void RemoveDependencies()
    {
        RemoveAxisLockConstraint();
    }

    private void RegisterForBeforeStepCallback()
    {
        if (!HaveRegisteredForBeforeStepCallback)
        {
            m_physicsScene.BeforeStep += PhysicsScene_BeforeStep;
            HaveRegisteredForBeforeStepCallback = true;
        }
    }

    private void UnRegisterForBeforeStepCallback()
    {
        if (HaveRegisteredForBeforeStepCallback)
        {
            m_physicsScene.BeforeStep -= PhysicsScene_BeforeStep;
            HaveRegisteredForBeforeStepCallback = false;
        }
    }

    private void PhysicsScene_BeforeStep(float timestep)
    {
        // If all the axis are free, we don't need to exist
        if (m_controllingPrim.LockedAngularAxis == m_controllingPrim.LockedAxisFree
                && m_controllingPrim.LockedLinearAxis == m_controllingPrim.LockedAxisFree)
        {
            Enabled = false;
        }

        // If the object is physically active, add the axis locking constraint
        if (isActive)
        {
            // Check to see if the locking parameters have changed
            if (m_controllingPrim.LockedLinearAxis != this.LockAxisLinearFlags
                || m_controllingPrim.LockedAngularAxis != this.LockAxisAngularFlags)
            {
                // The locking has changed. Remove the old constraint and build a new one
                RemoveAxisLockConstraint();
            }

            AddAxisLockConstraint();
        }
        else
        {
            RemoveAxisLockConstraint();
        }
    }

    // Note that this relies on being called at TaintTime
    private void AddAxisLockConstraint()
    {
        if (LockAxisConstraint == null)
        {
            // Lock that axis by creating a 6DOF constraint that has one end in the world and
            //    the other in the object.
            // http://www.bulletphysics.org/Bullet/phpBB3/viewtopic.php?p=20817
            // http://www.bulletphysics.org/Bullet/phpBB3/viewtopic.php?p=26380

            // Remove any existing axis constraint (just to be sure)
            RemoveAxisLockConstraint();

            BSConstraint6Dof axisConstrainer = new BSConstraint6Dof(m_physicsScene.World, m_controllingPrim.PhysBody,
                                OMV.Vector3.Zero, OMV.Quaternion.Identity,
                                false /* useLinearReferenceFrameB */, true /* disableCollisionsBetweenLinkedBodies */);
            LockAxisConstraint = axisConstrainer;
            m_physicsScene.Constraints.AddConstraint(LockAxisConstraint);

            // Remember the clocking being inforced so we can notice if they have changed
            LockAxisLinearFlags = m_controllingPrim.LockedLinearAxis;
            LockAxisAngularFlags = m_controllingPrim.LockedAngularAxis;

            // The constraint is tied to the world and oriented to the prim.

            if (!axisConstrainer.SetLinearLimits(m_controllingPrim.LockedLinearAxisLow, m_controllingPrim.LockedLinearAxisHigh))
            {
                m_physicsScene.DetailLog("{0},BSActorLockAxis.AddAxisLockConstraint,failedSetLinearLimits",
                        m_controllingPrim.LocalID);
            }

            if (!axisConstrainer.SetAngularLimits(m_controllingPrim.LockedAngularAxisLow, m_controllingPrim.LockedAngularAxisHigh))
            {
                m_physicsScene.DetailLog("{0},BSActorLockAxis.AddAxisLockConstraint,failedSetAngularLimits",
                        m_controllingPrim.LocalID);
            }

            m_physicsScene.DetailLog("{0},BSActorLockAxis.AddAxisLockConstraint,create,linLow={1},linHi={2},angLow={3},angHi={4}",
                                        m_controllingPrim.LocalID,
                                        m_controllingPrim.LockedLinearAxisLow,
                                        m_controllingPrim.LockedLinearAxisHigh,
                                        m_controllingPrim.LockedAngularAxisLow,
                                        m_controllingPrim.LockedAngularAxisHigh);

            // Constants from one of the posts mentioned above and used in Bullet's ConstraintDemo.
            axisConstrainer.TranslationalLimitMotor(true /* enable */, 5.0f, 0.1f);

            axisConstrainer.RecomputeConstraintVariables(m_controllingPrim.RawMass);

            RegisterForBeforeStepCallback();
        }
    }

    private void RemoveAxisLockConstraint()
    {
        UnRegisterForBeforeStepCallback();
        if (LockAxisConstraint != null)
        {
            m_physicsScene.Constraints.RemoveAndDestroyConstraint(LockAxisConstraint);
            LockAxisConstraint = null;
            m_physicsScene.DetailLog("{0},BSActorLockAxis.RemoveAxisLockConstraint,destroyingConstraint", m_controllingPrim.LocalID);
        }
    }
}
}