`On 3/21/07, Jiri Slaby <jirislaby@gmail.com> wrote:> STenyaK (Bruno González) napsal(a):> > On 3/14/07, Dmitry Torokhov <dmitry.torokhov@gmail.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.> >> > 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).>> So, the resolution is? Since I want no longer have out-of-kernel driver, I> need to know how to implement the phantom driver -- merge it `as is', i.e.> control through mmio or rewrite ff layer somehow, and in that case how?>> There seem to be only few possibilities:>> - new 3D effect, which will be problematic in any other future use, that may> need more than 3 axis. no matter if torques or vector is passed -- depending> on device and programmer (as I need to compute torques from forces in FP).> Maybe struct with 2x 3 axis is OK>> - "raw" effect, which may contain more axis, but this is ugly in Anssi's eyes>> - something else? (did I forget something)>I would suggest adding a new effect type (3d effect) and extending theunion in struct ff_effect.Let me know if I'm too vague, I already suggested that solution butgot no answer. I wonder if my mail got lost, nobody understood what Isaid, or if it's just a plain bad idea.For future devices with more than 3 FF-enabled axes, we can just dothe same, or develop a whole new API. There shouldn't be any worry.-- Johann-To unsubscribe from this list: send the line "unsubscribe linux-kernel" inthe body of a message to majordomo@vger.kernel.orgMore majordomo info at  http://vger.kernel.org/majordomo-info.htmlPlease read the FAQ at  http://www.tux.org/lkml/`