[Opensim-users] ubODE vs. Bullet (Ferd Frederix)
Rob Lindman
rob at roblindman.net
Tue May 2 07:08:35 UTC 2017
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
>
> To subscribe or unsubscribe via the World Wide Web, visit
> http://opensimulator.org/cgi-bin/mailman/listinfo/opensim-users
> or, via email, send a message with subject or body 'help' to
> opensim-users-request at opensimulator.org
>
> You can reach the person managing the list at
> opensim-users-owner at opensimulator.org
>
> When replying, please edit your Subject line so it is more specific
> than "Re: Contents of Opensim-users digest..."
>
>
> 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
> **********************************
>
>
> _______________________________________________
> Opensim-users mailing list
> Opensim-users at opensimulator.org
> http://opensimulator.org/cgi-bin/mailman/listinfo/opensim-users
>
> _______________________________________________
> Opensim-users mailing list
> Opensim-users at opensimulator.org
> http://opensimulator.org/cgi-bin/mailman/listinfo/opensim-users
>
> _______________________________________________
> Opensim-users mailing list
> Opensim-users at opensimulator.org
> http://opensimulator.org/cgi-bin/mailman/listinfo/opensim-users
More information about the Opensim-users
mailing list