[Opensim-users] ubODE vs. Bullet

[AJLDuarte]

Hi,

                ubOde and bullet where created in parallel so naturally had different interpretations of details and implementation.

                Making them more identical is a slow and hard going on process.

                To check if ubode or bullet are more corret on a feature, one needs to compare to original reference.

                This does not mean we will not add Opensim extensions, but those will be flagged as such

                Old ODE has its very own idea of vehicles (should no longer be used on new regions)

                On this case ubOde seems correct…  but then  im biased on that ;)

Ubit

 

From: opensim-users-bounces at opensimulator.org [mailto:opensim-users-bounces at opensimulator.org] On Behalf Of tringate at gmail.com
Sent: Monday, May 01, 2017 04:28
To: OS-Opensim Users
Subject: [Opensim-users] ubODE vs. Bullet

 

I am working on a script for a submarine and am having issues with it working fine in ubode but will not dive or surface in Bullet physics.

 

Here are the primary items that are involved with the physics.

 

This is the initial settings the object is set with.

 

set_engine(){

    llSetVehicleType(VEHICLE_TYPE_BOAT);

    llSetVehicleFloatParam(VEHICLE_LINEAR_DEFLECTION_TIMESCALE, 0.5);

    llSetVehicleFloatParam(VEHICLE_LINEAR_MOTOR_TIMESCALE, 0.1);

    llSetVehicleFloatParam(VEHICLE_LINEAR_MOTOR_DECAY_TIMESCALE, 0.1);

    llSetVehicleFloatParam(VEHICLE_LINEAR_DEFLECTION_EFFICIENCY, 0.80);

    llSetVehicleVectorParam(VEHICLE_LINEAR_FRICTION_TIMESCALE, <1, 1, 1>);        

    llSetVehicleFloatParam(VEHICLE_ANGULAR_DEFLECTION_EFFICIENCY, 0.2);

    llSetVehicleFloatParam(VEHICLE_ANGULAR_DEFLECTION_TIMESCALE, 1.0);

    llSetVehicleFloatParam(VEHICLE_ANGULAR_MOTOR_TIMESCALE, 0.5);

    llSetVehicleFloatParam(VEHICLE_ANGULAR_MOTOR_DECAY_TIMESCALE, 0.2);

    llSetVehicleVectorParam(VEHICLE_ANGULAR_FRICTION_TIMESCALE, <0.1, 0.1, 0.1>);

    llSetVehicleFloatParam(VEHICLE_VERTICAL_ATTRACTION_EFFICIENCY, 0.5);

    llSetVehicleFloatParam(VEHICLE_VERTICAL_ATTRACTION_TIMESCALE, 1.0);

    llSetVehicleFloatParam( VEHICLE_HOVER_HEIGHT, 0.0); // set ball at water surface

    llSetVehicleFloatParam( VEHICLE_HOVER_EFFICIENCY, 0.5 );

    llSetVehicleFloatParam( VEHICLE_HOVER_TIMESCALE, 1.0 ); 

}

 

These are the controls and they work fine in ubODE, but CONTROL_UP and CONTROL_DOWN do nothing in Bullet.

 

control(key id, integer level, integer edge)

    {

        float    gForwardThrust; // variable for forward thrust 

        float    gReverseThrust = -1.5; // reverse thrust backup speed

        if(level & CONTROL_FWD)

        {

            Swimming();

            gForwardThrust = 3; // normal forward speed

            vTarget = llGetPos(); // get our current position

            // if near region edge, slow down

            if (vTarget.x > xlimit || vTarget.x < gGuard || vTarget.y > ylimit || vTarget.y < gGuard) 

            {

                if (vTarget.x > xlimit) vTarget.x = xlimit;

                if (vTarget.x < gGuard) vTarget.x = gGuard;

                if (vTarget.y > xlimit) vTarget.y = ylimit;

                if (vTarget.y < gGuard) vTarget.y = gGuard;

                gForwardThrust = .3; // slow us down

                llWhisper(0, "Approaching sim edge, drive away...");

            }

            if ( vTarget.z < (llGround ( ZERO_VECTOR ) + 0.35) )

            {    // too shallow and going to collide with land

                gForwardThrust = .05; // slow us down

                llWhisper(0, "Too shallow, drive away...");

            }

            llSetVehicleVectorParam(VEHICLE_LINEAR_MOTOR_DIRECTION, <gForwardThrust,0,0>);

        }

        if(level & CONTROL_BACK)

        {

            llSetVehicleVectorParam(VEHICLE_LINEAR_MOTOR_DIRECTION, <gReverseThrust,0,0>); // back us up

            return;

        }

        if(level & (CONTROL_UP))

        {

            HovHeightBase = HovHeightBase + 0.02;

            llSetVehicleFloatParam( VEHICLE_HOVER_HEIGHT, HovHeightBase);

        }

        if(level & (CONTROL_DOWN))

        {

            HovHeightBase = HovHeightBase - 0.02;

            llSetVehicleFloatParam( VEHICLE_HOVER_HEIGHT, HovHeightBase);

        }

        if(level & (CONTROL_RIGHT|CONTROL_ROT_RIGHT)) llSetVehicleVectorParam(VEHICLE_ANGULAR_MOTOR_DIRECTION, <0, 0,-5.0>);

        if(level & (CONTROL_LEFT|CONTROL_ROT_LEFT)) llSetVehicleVectorParam(VEHICLE_ANGULAR_MOTOR_DIRECTION, <0, 0, 5.0>);

        if(edge & ~level & (CONTROL_FWD|CONTROL_BACK)) Treading();

    }

 

I might add this is actually from my swim ball script which also works just fine in ubODE but fails in Bullet on the dive and surface actions.

 

In bullet nothing at all happens.

 

Is this a bug in opensim?  I know it is expected a script that works in one physics engine is suppose to work in the other physics engines as well.

 

Not being an expert at script writing, it is possible I stumbled into doing something wrong that ubODE can deal with and Bullet can’t.

 

Tom

 

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