Thanks, Nate. Sorry I didn't see it before.

On 8/11/06, Nate Koenig <nkoenig@robotics.usc.edu> wrote:
So, to answer Jordi's concerns first.

Collada is used to specify 3d meshes. This means their vertex
coordinates, texture coordinates, normals, etc, etc. Gazebo doesn't
care about any of that. Let a 3d modeler create the mesh. The gui that
we will use is not 3d modeler. It will only allow a person to load in
mesh, position it however they desire, connect joints, etc. The GUI
will not let the person edit the mesh itself.

Here are the core features of Collada:
   * Mesh geometry
   * Skinning
   * Morphing
   * Animation
   * Assets
   * Data validation
Gazebo needs none of them.


There are a couple goals I have in mind for gazebo, all of which I
have put on the wiki:
http://playerstage.sourceforge.net/wiki/Gazebo#Todo_List. If you have
more good ideas, please add them. If you want to take on a task, just
put down your name.

-nate

On 8/11/06, Douglas Thom < douglas.thom@gmail.com> wrote:
>
> Is there any statement anywhere about the goals or objectives, components
> and requirements of this project? I had a look around and don't see any. Is
> it worth doing or do the primaries on this project pretty much have the
> vision of the system. I'm just thinking that if we had a clear idea on what
> we need then it's a matter of seeing which tool out there comes closest
> (balanced with its apparent survivability and so on but you get the idea).
>
> Or are we using this discussion to ratify those requirements?
>
>
>
> On 8/11/06, Jordi <mumismo@gmail.com> wrote:
> >
> >
> >
> >
> >
> >
> > > Let's take a step back for a moment, and consider what gazebo really
> > > needs in a XML format. We will have two types of files, one that
> > > describes the world and one that describes a model. A model is
> > > collection of bodies connected via joints and zero or more sensors. A
> > > world is a collection of models along with some global parameters such
> > > as gravity.
> > >
> > > We don't need collada or X3D to specify the world. Our current format
> > > is pretty good.
> >
> > Agree
> >
> >
> > > For the model file, we may not need Collada or X3D. Ogre3d allows us
> > > to directly load meshes from file. So a body's geometry will now be
> > > specified by a mesh file. This mesh can be created from almost any 3d
> > > modeler, such as blender. So a model file will contain the following:
> > >   1) 1...N bodies, where each body contains a mesh file, and some
> > > simple properties such as scale, position, color, texture, mass, etc.
> > >   2) 0...M joints, where each joint connects two bodies together via a
> > > specific ODE joint type.
> > >   3) 0...K sensors, where each sensor contains a position on the model
> > > and a sensor type.
> >
> > Disagree.
> >
> > I guess that you are thinking in using external 3D tools to make meshes
> that
> > will be referenced from the XML to build the model. The XML file should be
> > easy enough to be done MANUALLY. It works well, in theory (or with really
> > really easy models).
> >
> > As we move to XML models, we lose a lot of interesting information. We
> lose
> > the C++ code. You may think this is ok, but let me  provide an example:
> >
> > >From the carchassis model (pretty simple, uh?)
> >
> > chassisSize = GzVectorSet(wheelBase, trackWidth - wheelDiam, 0.5);
> > chassisPos = GzVectorSet(0, 0, frameClear + chassisSize.z / 2);
> >
> > rearLeftPose = GzPoseSet(GzVectorSet(-wheelBase / 2,
> +trackWidth / 2,
> > wheelDiam / 2),
> >                           GzQuaternFromAxis(1, 0, 0,
> -M_PI / 2));
> > rearRightPose = GzPoseSet(GzVectorSet(-wheelBase / 2,
> -trackWidth / 2,
> > wheelDiam / 2),
> >                            GzQuaternFromAxis(1, 0, 0, +M_PI / 2));
> >
> > frontLeftPose = GzPoseSet(GzVectorSet(+wheelBase / 2,
> +trackWidth / 2,
> > wheelDiam / 2),
> >                            GzQuaternFromAxis(1, 0, 0, -M_PI / 2));
> > frontRightPose = GzPoseSet(GzVectorSet(+wheelBase / 2,
> -trackWidth / 2,
> > wheelDiam / 2),
> >                             GzQuaternFromAxis(1, 0, 0,
> +M_PI / 2));
> >
> >
> >
> > In a XML everything turns to numbers. Numbers like 0.254, 0.208, 1.560 ...
> >
> >
> > I have pretty bad imagination when it comes to put those positions,
> rotations,
> > scales, colors and shapes in a 3D world, so I CAN'T do those XML files by
> > hand.
> >
> > Too error prone.
> >
> >
> > So we need a GUI to make these files.
> >
> > And why not use COLLADA or X3D when they have widespread adoption in 3D
> > modelers?
> >
> >
> >
> > > Our application is specific to robotic
> > > simulation, we probably don't even have to mess around with a standard
> > > 3d Model data format - just let Ogre3d take care of loading meshes and
> > > 3d modelers creating them.
> >
> > Mostly agree.
> >
> > We don't have to mess with COLLADA (it's just a tool to help us), Ogre3D
> and
> > ODE automagically load it (loading the referred meshes IIRC). X3D should
> need
> > some more work if we choose that path.
> >
> > We will ALWAYS need our very specifics tags in any format we choose, as
> our
> > problem is very specific. My point is let other projects help us as much
> as
> > possible and focus our development in only those tags, not on the entire
> XML
> > format.
> >
> >
> > So just to repeat myself once more:
> > Loading one mesh, loads for instance a wheel of a robot, cool.
> > Loading a COLLADA file, loads every wheel of our robot (and everything
> else)
> > with their physical properties.
> > Loading any of them cost us the same effort, call the load method from
> Ogre3D.
> >
> >
> > --
> > Jordi Polo
> >
> >
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> >
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> >
>
>
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