[Opensim-users] ubODE vs. Bullet (Ferd Frederix)
Rob Lindman
rob at roblindman.net
Tue May 2 08:44:04 UTC 2017
Hi,
Thanks for doing it wrong in spite of knowing otherwise.
Regards.
On Tue, 2 May 2017 09:24:04 +0100
"AJLDuarte" <ajlduarte at sapo.pt> wrote:
> Hi,
> Thanks for telling things everyone already knows
> Regards,
> UBit
>
>
> -----Original Message-----
> From: opensim-users-bounces at opensimulator.org
> [mailto:opensim-users-bounces at opensimulator.org] On Behalf Of Rob
> Lindman Sent: Tuesday, May 02, 2017 08:09 To:
> opensim-users at opensimulator.org Subject: Re: [Opensim-users] ubODE
> vs. Bullet (Ferd Frederix)
>
> Hi,
>
> The user expectation will most likely be 'this script I wrote in
> Second Life should work in OpenSim' and if this is some 'reinvent the
> wheel by way of deformity' then my assessment is it is being done
> incorrectly.
>
> If there's some desire to make it 'work differently' then the
> recommendation is call it something else... rename all of the
> constants to UBODE_WHATNOT and all of the functions to
> osFunctionWhatever and then you will not be colliding with a
> pre-existing expectation.
>
> Otherwise, OpenSim becomes a wolf-in-sheep's-clothing... looking like
> a duck, walking like a duck, and barking like a bowl of oatmeal. It
> won't make sense to people.
>
> Me
>
>
> On Mon, 1 May 2017 21:52:06 -0400
> <tringate at gmail.com> wrote:
>
> > Ubit,
> >
> > I appreciate the information. It certainly helps me understand
> > what some of these functions do.
> >
> > I have been thinking about changing over to using ubOde now for
> > awhile. Many months ago when I tried doing that my residents went
> > nuts because so many things stopped working or worked differently.
> > I have been running it on my personal region now for maybe 6 months
> > and I have not noticed any strange problems, but then I don't have
> > a lot of the glitzy things some of my residents like to use.
> >
> >
> >
> > -----Original Message-----
> > From: AJLDuarte
> > Sent: Monday, May 1, 2017 12:51 PM
> > To: opensim-users at opensimulator.org
> > Subject: Re: [Opensim-users] ubODE vs. Bullet (Ferd Frederix)
> >
> > Hi just a few more notes about ubOde:
> >
> > VEHICLE_FLAG_HOVER_GLOBAL_HEIGHT is dominant, if present
> > VEHICLE_HOVER_HEIGHT is a region height Else it is a height
> > relative to water and or terrain according to:
> >
> > If VEHICLE_FLAG_HOVER_WATER_ONLY is present, water is the
> > reference, terrain is ignored Else if HOVER_TERRAIN_ONLY is present
> > terrain is used, water is ignored.
> > Else it none of this two are presence the higher height of terrain
> > or water is used
> >
> > VEHICLE_HOVER_HEIGHT can be a negative value but under the generic
> > constrain that objects can't go (much) underground.
> >
> > VEHICLE_HOVER is disabled by setting VEHICLE_HOVER_TIMESCALE higher
> > than 300, not height of zero.
> >
> > Regards,
> > Ubit
> >
> >
> > -----Original Message-----
> > From: opensim-users-bounces at opensimulator.org
> > [mailto:opensim-users-bounces at opensimulator.org] On Behalf Of
> > AJLDuarte Sent: Monday, May 01, 2017 16:16
> > To: opensim-users at opensimulator.org
> > Subject: Re: [Opensim-users] ubODE vs. Bullet (Ferd Frederix)
> >
> > Hi,
> > Sorry Fred, this is not correct
> > VEHICLE_HOVER_HEIGHT can work with terrain, water, higher of both,
> > or fixed value.
> > This is controlled by flags:
> >
> > VEHICLE_FLAG_HOVER_GLOBAL_HEIGHT
> > VEHICLE_FLAG_HOVER_WATER_ONLY
> > VEHICLE_FLAG_HOVER_TERRAIN_ONLY
> >
> > Each vehicle sets defaults for this, and they be present at same
> > time, giving unpredictable results according to wiki I did added a
> > hierarchy on this flags in ubOde to reduce unpredictability, but
> > sure that’s not like the one on bullet, if any.
> > So we should use llRemoveVehicleFlags() to remove the ones we don't
> > want, before llSetVehicleFlags();
> >
> > We also have VEHICLE_FLAG_HOVER_UP_ONLY...
> >
> > See http://wiki.secondlife.com/wiki/Linden_Vehicle_Tutorial and
> > links on it for more information.
> >
> > ubOde will try to follow VEHICLE_HOVER_HEIGHT on the fly subject to
> > timescale and efficiency (ie how fast) In fact it will also follow
> > region water level changes on the fly subject to same parameters
> >
> > Also keep in mind that using llSetPos(), setvelocity, and similar
> > should be avoid on physics objects in active simulation, specially
> > vehicles.
> >
> > Ubit.
> >
> >
> > From: opensim-users-bounces at opensimulator.org
> > [mailto:opensim-users-bounces at opensimulator.org] On Behalf Of Fred
> > Beckhusen Sent: Monday, May 01, 2017 15:46
> > To: opensim-users at opensimulator.org
> > Subject: Re: [Opensim-users] ubODE vs. Bullet (Ferd Frederix)
> >
> > Tom, I think this is a difference in implementation details. To
> > me, Bullet actually gets it correct. Your script is setting Hover
> > height to go up and down. It is effectively llSetVehicleFloatParam(
> > VEHICLE_HOVER_HEIGHT, HovHeightBase += .02 ); each click Up and -=
> > 0.02 on Down, while starting from a negative
> > value. Zero is water height (typically 20 meters). Water height
> > can range from 0 to +100 in a sim.
> > The problem is that VEHICLE_HOVER_HEIGHT is for use only above
> > ground. It is not defined in LSL by Second Life for use with
> > negative numbers, with additional proof of this is that zero (water
> > height) disables it entirely. So it is implementation specific. I
> > would chalk this up as expected behavior in Bullet. Try adding a
> > float Z variable to your VEHICLE_LINEAR_MOTOR_DIRECTION and add or
> > subtract a small amount from the Z (up) axis. Your axis seems
> > suspicious. In vehicles, X is forward/back, Y is L-R, and Z is up.
> > Your script right and left controls are setting
> > VEHICLE_ANGULAR_MOTOR_DIRECTION, <0, 0, 5.0>, which is mucking
> > around with Z (Up). Sounds correct for a prim that rotates around
> > Z, but not for a vehicle. I could be wrong here. There may be a
> > VEHICLE_REFERENCE_FRAME set in your script elsewhere that is
> > overriding the reference axis, so be wary of it. Also, take a look
> > at the function llWater(), and think about doing this:
> >
> > vector water = llWater(ZERO_VECTOR);
> > HovHeightBase += water.z - 20;
> >
> > This will handle sims where water is at a different level.
> > regards and good luck:\
> > Ferd Frederix/Fred Beckhusen
> >
> > On 2017-05-01 5:20 AM, opensim-users-request at opensimulator.org
> > wrote: Send Opensim-users mailing list submissions to
> > opensim-users at opensimulator.org
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> >
> > Today's Topics:
> >
> > 1. ubODE vs. Bullet (tringate at gmail.com)
> > 2. Re: ubODE vs. Bullet (AJLDuarte)
> >
> >
> > ----------------------------------------------------------------------
> >
> > Message: 1
> > Date: Sun, 30 Apr 2017 23:27:37 -0400
> > From: <tringate at gmail.com>
> > To: "OS-Opensim Users" <opensim-users at opensimulator.org>
> > Subject: [Opensim-users] ubODE vs. Bullet
> > Message-ID: <65ED585961044A12B8C19EA5984238E3 at TomsDesktop>
> > Content-Type: text/plain; charset="utf-8"
> >
> > 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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