Re: [Celestia-developers] SkyPlane reference frame
Real-time 3D visualization of space
Status: Beta
Brought to you by:
cjlaurel
From: Chris L. <cl...@gm...> - 2010-02-03 20:31:53
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Completely sensible. If you feel the code is ready, please check in your current implementation of SkyPlane. --Chris On Sat, Jan 30, 2010 at 5:44 AM, Andrew Tribick <ajt...@go...> wrote: > Well this is how I was originally thinking: if we want to add in more > parameters it should be possible to do this later if we have more of > the observer-friendly reference frames available (e.g. your proposed > EquatorMeanOfDate idea). Since most of the utility is in the choice of > defaults (SkyPlane is essentially a quick way of specifying a far more > verbose TwoVector definition), might as well leave it minimal for now > and if there's significant call to expand the functionality, do it > then. > > Andrew > > On 27 January 2010 23:55, Chris Laurel <cl...@gm...> wrote: >> Andrew, >> >> The SkyPlane frame is quite useful as you've implemented it. With the >> ability to specify an alternate origin and north vector, it's >> basically a TwoVector frame with some handy defaults. That's not a >> terrible thing, but it does mean that once you want to do something >> non-standard, you're going most of the way down the frames rabbit >> hole... >> >> SkyPlane >> { >> North { ConstantVector { Vector [ 0 0 1 ] Frame { EquatorMeanOfDate {} } } } >> } >> >> (The EquatorMeanOfDate frame doesn't currently exist, but it would be >> a useful addition...) >> >> A less flexible alternative would only let you specify the frame for >> the north vector: >> >> SkyPlane >> { >> NorthFrame { EquatorMeanOfDate {} } >> } >> >> Which (if any) seems like a better option? >> >> --Chris >> >> On Mon, Jan 25, 2010 at 1:06 PM, Andrew Tribick >> <ajt...@go...> wrote: >>> So it seems like a good idea to add a parameter to specify the North >>> vector, probably easiest to make this parameter interpreted in the >>> same way as the Primary and Secondary parameters in the TwoVector >>> frame. What about the ability to specify the origin - might it make >>> sense to be able to specify the Earth instead of the coordinate origin >>> for example? >>> >>> Andrew >>> >>> 2010/1/25 Selden E Ball Jr <se...@co...>: >>>> A google search did locate a handful of uses of the sky plane and >>>> the equator of date, primarily for measurements of the ring planes >>>> of Uranus and Neptune. >>>> >>>> s. >>>> >>>>> Andrew, >>>> >>>>> This patch looks good. I think that you made the right choice to use an >>>>> absolute position vector even though this is less general than an >>>>> implementation that would let you specify both an observer and target >>>>> object. The only suggestion I would make is to clarify what is meant by >>>>> 'celestial north.' From the code, it's clear that it's +z in the J2000 >>>>> equator frame (Earth mean equator and equinox of J2000), but we should make >>>>> sure that this is clearly documented. Does anyone every use the mean or true >>>>> equator *of date* as the basis for a sky plane coordinate system? It seems >>>>> like a bad idea, but perhaps some astronomer has a reason. >>>> >>>>> --Chris >>>> >>>>> On Sat, Jan 23, 2010 at 11:50 AM, Andrew Tribick >>>>> <ajt...@go...>wrote: >>>> >>>>> > Hello, >>>>> > >>>>> > The attached patch implements a SkyPlane reference frame that sets up >>>>> > the z-axis pointing towards the coordinate origin and the x-axis >>>>> > pointing towards Celestial north. This is the reference frame for >>>>> > which Grant's orbit transformation spreadsheet is used. >>>>> > >>>>> > The syntax is >>>>> > >>>>> > SkyPlane { >>>>> > Center <object> >>>>> > Target <object> >>>>> > } >>>>> > >>>>> > The reference frame is set up so that the z-axis points from the >>>>> > Target object to the coordinate origin. Target defaults to the >>>>> > highest-level ancestor which generally ends up as a fixed-position >>>>> > star or barycenter. This prevents slight orbital precession if this is >>>>> > used in combination with multiple star systems (for example). The >>>>> > default for Center is as per usual with reference frames. >>>>> > >>>>> > At present reference frames are only supported in .ssc files, however >>>>> > this particular reference frame is probably worth implementing for >>>>> > stars as well. Even without extending to .stc files, it should be >>>>> > useful for the exoplanets catalogue to have this frame available. >>>>> > >>>>> > Regards, >>>>> > Andrew >>>>> > >>>>> > >>>>> > ------------------------------------------------------------------------------ >>>>> > Throughout its 18-year history, RSA Conference consistently attracts the >>>>> > world's best and brightest in the field, creating opportunities for >>>>> > Conference >>>>> > attendees to learn about information security's most important issues >>>>> > through >>>>> > interactions with peers, luminaries and emerging and established companies. >>>>> > http://p.sf.net/sfu/rsaconf-dev2dev >>>>> > _______________________________________________ >>>>> > Celestia-developers mailing list >>>>> > Cel...@li... >>>>> > https://lists.sourceforge.net/lists/listinfo/celestia-developers >>>>> > >>>>> > >>>> >>>> ------------------------------------------------------------------------------ >>>> Throughout its 18-year history, RSA Conference consistently attracts the >>>> world's best and brightest in the field, creating opportunities for Conference >>>> attendees to learn about information security's most important issues through >>>> interactions with peers, luminaries and emerging and established companies. >>>> http://p.sf.net/sfu/rsaconf-dev2dev >>>> _______________________________________________ >>>> Celestia-developers mailing list >>>> Cel...@li... >>>> https://lists.sourceforge.net/lists/listinfo/celestia-developers >>>> >>> >>> ------------------------------------------------------------------------------ >>> The Planet: dedicated and managed hosting, cloud storage, colocation >>> Stay online with enterprise data centers and the best network in the business >>> Choose flexible plans and management services without long-term contracts >>> Personal 24x7 support from experience hosting pros just a phone call away. >>> http://p.sf.net/sfu/theplanet-com >>> _______________________________________________ >>> Celestia-developers mailing list >>> Cel...@li... >>> https://lists.sourceforge.net/lists/listinfo/celestia-developers >>> >> > |