From: throopw@sheol.org (Wayne Throop) Newsgroups: rec.arts.sf.tv.babylon5.moderated Subject: Re: C&C starfield (Q&A) Distribution: world Organization: sheol Message-ID: <841846108@sheol.org> Date: Wed, 04 Sep 1996 14:08:28 GMT References: <3224FE4A.2533@moon.jic.com> <503clo$ud@newsbf02.news.aol.com> <841373518@sheol.org> <322D2290.749C@rconnect.com> ::: jmsatb5@aol.com (Jms at B5) ::: C&C rotates *below* the center of the station [...] ::: So the rotation wouldn't be at the center of the window, ::: but rather above it [...] ::: you'd have to build a *round* starfield about 30 feet high :: throopw@sheol.org (Wayne Throop) :: This seems to be a mistake of some sort. :: stars would rotate around the line of sight parallel to the station axis : Chris Abbey : Only if the viewer's eye was aligned with the rotational axis; IOW the : rotational axis passed directly throught the pupil of the eye and : parralleled the line of sight. (already impossible for the normal : bi-nocular human) Hmmmm. I'm a binocular human, and when I look at 45-ish degrees into the north sky (parallel to earth's spin axis), the sky spins around my viewpoint, and I'm looking at the same star as somebody looking straight up from the pole, even though I'm 4000-ish kilometers off to the side. To simulate this for me, you don't have to make a 4000-kilometer wheel above my head. For the C&C staff, their level-line-of-sight out the window is parallel to the spin (because level-in-C&C-gravity is actually a cylinder about the spin axis, and the window is about eye height). If they stand square in front of the window (that is, if their line of sight out the window is perpendicular to the plane of an ideal endcap of the station), the starfield will spin about the center of the window. It will not be swooping past the window. You don't need a 30-foot wheel because of the axial offset of the window, any more than you'd need a 4000-kilometer wheel because of my offset from the north pole. I'm quite certain of this. Thanks to Chris for providing a reasonable and even-toned counterargument/explanation, but it doesn't convince me. :: Perhaps the 30 foot high wheel was needed to get sufficient angular coverage : Doubtfully, it's a fairly small window and I'm sure they pre-plan : they're camera angels well enough to re-position any "scenery" behind : the window so as to use something only slightly larger than the window. Right, right, in terms of the *size* of any one bit of scenery. But if that bit of scenery is motionless WRT the "fixed stars" (or *consists* of a field of "fixed stars"), then somebody standing several feet off to one side or another of C&C will have a line-of-sight out the window which will not include the intersection of the station axis with the fixed background stars. Thus, they would "swoop" or "sweep" instead of "spin". My suggestion was, you'd need a 30 foot wheel to get this "sweep" to be accurate for camera viewpoints "off to the side" in C&C; to get adequate "angular coverage" of camera placement, not "angular coverage" of what's seen out the window. Note that, the 30 foot wheel would *still* need to be spinning about a point directly outside the C&C window, not "above" it centered on a notional station spin axis. Again, I'm not particularly questioning that the effect is impractical, or that a 30-foot wheel might be needed. I'm just still not convinced that it's needed *because* *of* C&C's offset from station spin axis. :: I think the views out the observation rooms in the first season, with :: G'Kar leading the ceremony, and a couple other shots, [were] done quite :: correctly : IIRC this was CGI, too expensive for your daily C&C shots. Agreed. I merely was refering to my memory of the placement of spin axis in the visual field. I'll have to recheck those scenes... I can remember thinking they weren't right at first, but then noting the viewing angle was from a doorway above the scene. As I say; I'll have to check again. -- Wayne Throop throopw@sheol.org http://sheol.org/throopw throopw@cisco.com