[x3d-public] Gravity Sensor?

Fri Apr 24 21:47:17 PDT 2015

Yes Christoph, I was speaking of our own experience with this at Office Towers, as we have several types of vehicles running. In our case, the vehicles themselves are the containers, but that doesn't keep the browser from seeing movements, thus triggering the "walk" gesture. Some field needs to be passed to the avatars, to override the browser action when inside moving vehicles, while still allowing said gesture within the vehicles themselves. 

As far as gravity and physics, we'd like to see a simple node that would allow any object to behave much like an avatar as defined by the browser, without having to deal with collision detection in every instance. Avatars fall to the highest elevation, don't go through walls, etc., and they do this automatically. We'd need the ability to have objects do the same as needed, so cars don't go through buildings and flying machines don't go below ground, unless we want to. Cheers, Lauren     

-----Original Message-----
From: x3d-public [mailto:x3d-public-bounces at web3d.org] On Behalf Of Christoph Valentin
Sent: Friday, April 24, 2015 4:22 PM
To: x3d-public at 3dnpvei.com
Cc: x3d-public at web3d.org
Subject: Re: [x3d-public] Gravity Sensor?

Hi Lauren,

I know the problem with the default "Walk" gesture of Avatars, when they enter the locomotive or the Boat in SrrTrains demo scene.

Imho, this is caused by the fact, that the pilot avatar is not "hung up" within some <Transform> node in the scene, but it is "hung up" directly at the Browser. I guess they do it to avoid the chitter when 3rd person view.

A similar effect: I scaled a module with "scale < 1" and bound a viewpoint within this module. The pilot avatar remains big, but the drone avatars are correctly scaled, because I hang them up in "Avatar Containers" at the correct place within the scene.

All the best 

Gesendet: Freitag, 24. April 2015 um 16:57 Uhr
Von: GLG <x3d-public at 3dnpvei.com>
An: "'Christoph Valentin'" <christoph.valentin at gmx.at>
Cc: x3d-public at web3d.org
Betreff: RE: [x3d-public] Gravity Sensor?
Another issue I experience with this is that, avatars begin the default 'Walk' gesture when inside moving subway trains (or other moving vehicles), which is obviously incorrect, they should stand or sit still. Avatars will need to know this, so the gesture is not triggered, but then again, they should be able to walk normally inside a boat, train, airplane or spaceship, independently of the vehicle's motion. A bit tricky to implement when factoring in a multiuser system. Cheers, Lauren

-----Original Message-----
From: x3d-public [mailto:x3d-public-bounces at web3d.org] On Behalf Of Christoph Valentin
Sent: Friday, April 24, 2015 10:17 AM
To: x3d-public at 3dnpvei.com; Roy Walmsley
Cc: x3d-public at web3d.org
Subject: Re: [x3d-public] Gravity Sensor?

Thanks Lauren and Roy,

My question was from a theoretical perspective (maybe I will do some trials with GeoSpatial component soon).

Thinking about railway cars, that contain scenery and avatar can enter. --> need superposition of gravity and inertial forces (from the acceleration of the railway car).

KR

Gesendet: Freitag, 24. April 2015 um 14:12 Uhr
Von: GLG <x3d-public at 3dnpvei.com>
An: x3d-public at web3d.org
Betreff: Re: [x3d-public] Gravity Sensor?
Yes there's ParticleSystems (thanks Roy), maybe the
X3DParticlePhysicsModelNode in particular is what you're looking for, or the
X3DParticlePhysicsModelNode. Cheers, Lauren

40.4.4 ForcePhysicsModel

GravityPhysicsModel : X3DParticlePhysicsModelNode {
SFBool [in,out] enabled TRUE
SFVec3f [in,out] force 0 -9.8 0 (∞,∞)
SFNode [in,out] metadata NULL [X3DMetadataObject]
}
The ForcePhysicsModel node specifies a physics model that applies a constant
force value to the particles. Force may act in any given direction vector at
any strength.

The force field is used to indicate the strength and direction of the force
(e.g., gravity) that should be applied. Force is specified in metres per
seconds-squared (m/s2). If the particles are defined to have zero mass by
the emitter, the ForcePhysicsModel node has no effect.

40.4.1 BoundedPhysicsModel

BoundedPhysicsModel : X3DParticlePhysicsModelNode {
SFBool [in,out] enabled TRUE
SFNode [in,out] geometry NULL [X3DGeometryNode]
SFNode [in,out] metadata NULL [X3DMetadataObject]
}
The BoundedPhysicsModel node specifies a physics model that applies a
user-defined set of geometrical bounds to the particles.

The geometry field specifies a piece of geometry that models the bounds that
constrain the location of the particles. When a particle touches the surface
of the bounds, it is reflected. The particles may be restricted to an inside
location or an outside location. All geometry defined by the bounds are
considered to be non-solid, regardless of the setting of the solid field. It
does not matter whether the particle impacts the front or back side of the
geometry. Particles are reflected at the same angle to the normal of the
surface to which they impact, continuing in the same direction. The
calculation of the correct normal is determined by the rules of the geometry
that forms the bounds.

EXAMPLE A particle can be made to bounce off an elevation grid representing
terrain.

http://www.web3d.org/documents/specifications/19775-1/V3.2/Part01/components
/particle_systems.html

-----Original Message-----
From: x3d-public [mailto:x3d-public-bounces at web3d.org] On Behalf Of Roy
Walmsley
Sent: Friday, April 24, 2015 5:31 AM
To: 'Christoph Valentin'; 'X3D Graphics public mailing list'
Subject: Re: [x3d-public] Gravity Sensor?

Christoph,

In X3D the only place where forces, including gravity, can be included is in
the Particle systems component.

There isn't anything like a "gravity sensor". You have to take care of it
yourself. This could be done using external code and interacting through the
SAI. Alternatively, you could use a Script node to keep everything internal
to the scene.

>From your reasoning point d) I am assuming you are working with the
GeoSpatial component. What sort of things do you want to apply gravity to?

Roy

-----Original Message-----
From: x3d-public [mailto:x3d-public-bounces at web3d.org] On Behalf Of
Christoph Valentin
Sent: 24 April 2015 10:04
To: X3D Graphics public mailing list
Subject: [x3d-public] Gravity Sensor?

A few questions to the community.

Is there something like a "gravity sensor" in X3D/VRML?

Reasoning:

a) The Web3D Browser cares for gravity and collision detection, when
controlling the movement of the avatar.
b) However, when controlling the dynamics of an arbitrary object, I have to
care for gravity and collision myself
c) In classical scenes, the gravity is 9.81 m.s^-2 in -y direction, no
problem
d) But how to calculate gravity in an X3D-Earth scene? Don't we need a kind
of "gravity sensor" here?

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