linux-kernel - Re: FF layer restrictions [Was: [PATCH 1/1] Input: add sensable phantom driver]

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Date:	Thu, 15 Mar 2007 21:51:07 +0100
From:	"johann deneux" <johann.deneux@...il.com>
To:	"STenyaK (Bruno González)" <stenyak@...il.com>
Cc:	"Dmitry Torokhov" <dmitry.torokhov@...il.com>,
	"Anssi Hannula" <anssi.hannula@...il.com>,
	"Jiri Slaby" <jirislaby@...il.com>,
	"Linux kernel mailing list" <linux-kernel@...r.kernel.org>,
	linux-input@...ey.karlin.mff.cuni.cz
Subject: Re: FF layer restrictions [Was: [PATCH 1/1] Input: add sensable phantom driver]

On 3/14/07, STenyaK (Bruno González) <stenyak@...il.com> wrote:
> On 3/14/07, Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
> > > I have a question: if the force is to be 3D, why only 3 possible values?
> > > What would they be, 3 torques or 3 forces? In the case of car sims (ff
> > > steering wheels), only one axis of torque is usually used (except for 6 dof
> > > platforms, as mentioned).
> > >
> >
> > I wonder if we could somehow extend or augment FF envelope se we could
> > specify a plane for the effect.. Then a vector could be represented by
> > a sum 3 constant effects in 3 separate planes and we could also use
> > spring and other effects as well.
>

I would think one plane and one axis is all that's needed for a 3d vector, or?
Do we understand eachother?

> Ideally, afaik we should use:
> -3 values for translation force (linear force): x,y,z components of
> the force vector.
> -4 values for rotation force (torque): x,y,z,w components of the
> quaternion. You can also use euler angles (and i think there are
> another one or two notations), which is just 3 values, but i'm not
> sure it will be a correct decision (due to the gimbal lock problem,
> which may or may not be present in ff devices, dunno).

Same remark here. A torque is a 3-dimensional thing, just like a
force. What for do you need 4 components?

-- 
Johann
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