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#1
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Celestial sphere image?
Hello, all!
As I've mentioned before, I'm making some animations to show Earth's rotation, orbit, precession, and all that other fun rotational stuff. Blame it on Oriel. I've got everything done save for a star field background. Yes, I know you can't really see the stars if the lighted portion of Earth is also in-frame, but I want them anyway. Artistic license and all that. Blender has a nifty utility that will generate a fairly good looking star field background, and I'll use that if I have to. I'd rather have an accurate celestial sphere, though. For this to work, I need a rectangular image that I can coordinate transform onto a sphere. In 3D modeling parlance, it's called UV mapping--because you coordinate transform Cartesian x and y coordinates into spherical coordinates u and v (with r assumed constant). Think of it as a Mercator projection in reverse... although it's not exatly the same thing. Does anyone know of an image suitable for UV mapping onto a sphere that would generate an accurate celestial sphere? I suppose my only other realistic option would be to obtain a star catalog and write a Mathematica routine to grab all stars below magnitude m and project them on to a plane, then export the whole shebang as a honkin' big jpeg or PNG that Blender can then wrap onto a sphere. Any other ideas on how I might approach this? Thanks! -- Dave |
#2
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Celestial sphere image?
Dave Typinski wrote in
news Does anyone know of an image suitable for UV mapping onto a sphere that would generate an accurate celestial sphere? I recently had the same need and I ran across the following: http://www.oera.net/How2/TextureMaps.htm The planetary textures are just fine, as long as you don't try a low altitude fly by. However, I found the star map to be of insufficient resolution at only 2500x1250. This resulted in big blurry blotches of stars when rendered at higher resolutions. But then again, it may be good enough for your needs. Or perhaps I'm just being nitpicky. I'd love to find a similar UV map at a resolution at 4 times that - 10000x5000. Or, figure out how to make one myself. hmmm...this reminds me... I never did finish that animation project. It had a similar purpose, to debunk a 'theory'. Brian -- http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html Quake "predictions": http://www.skywise711.com/quakes/EQDB/index.html Sed quis custodiet ipsos Custodes? |
#3
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Celestial sphere image?
Skywise wrote:
Dave Typinski wrote in news Does anyone know of an image suitable for UV mapping onto a sphere that would generate an accurate celestial sphere? I recently had the same need and I ran across the following: http://www.oera.net/How2/TextureMaps.htm That's great! Thank you! I like his Earth Texture Atmospherical, too... the colors look like they might actually work better than the one I got from this great place, which seems to specialize in super-high-resolution stuff: http://planetpixelemporium.com/earth.html The planetary textures are just fine, as long as you don't try a low altitude fly by. However, I found the star map to be of insufficient resolution at only 2500x1250. This resulted in big blurry blotches of stars when rendered at higher resolutions. I'm going to try it both ways: with this UV map and some fake ones I made using Blender's "stars" background feature. The celestial sphere would work fine for a view from L5, but it won't work for a view looking down on the Earth from above the N pole. As the Earth orbits in the model, the stars would seem to shift. It's a model-space thing: Blender really doesn't like it when you try to put something an infinite distance away, or even very large, for that matter. My setup doesn't want to render anything further than about 100 "Blender units" away from the camera. ....unless you parented the celestial sphere to the same empty that the Earth was parented to, but didn't make it rotate. That would work! Hm. I forsee more lilly-gilding to be done on this animation. Yessir, there is definitely more than one way to skin a cat. But then again, it may be good enough for your needs. Or perhaps I'm just being nitpicky. Not at all. It looks a bit dark, but some massaging with Photoshop oughtta bring things up a bit. Or not. Great resource either way. I'd love to find a similar UV map at a resolution at 4 times that - 10000x5000. Or, figure out how to make one myself. Well, if I ever get to it, I could write a Mathematica routine to do it. All I need is a star catalog listing RA, Dec, Mag, and spectral class. Still wouldn't grab any diffuse objects, though. Come to think of it, with Blender's Python scripting ability, you could probably parse the files and create the thing right in Blender. hmmm...this reminds me... I never did finish that animation project. It had a similar purpose, to debunk a 'theory'. Oh? What theory was that? -- Dave |
#4
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Celestial sphere image?
On May 11, 1:57*am, Dave Typinski wrote:
Hello, all! As I've mentioned before, I'm making some animations to show Earth's rotation, orbit, precession, and all that other fun rotational stuff. Blame it on Oriel. * That's right, you equate a rotating celestial sphere with a stationary Earth and its obverse, a rotating Earth to celestial sphere geometry and this subhuman ideology surfaces in something you 'celebrate' and consider as something actual - 1) There is no center of the universe, because expansion happens uniformly everywhere. 2) There is a center of the universe, because it has a bounding volume Six centuries after Archbishop Cusa recognized the need to discover the motions of the Earth or rather,to find suitable arguments to get rid of celestial sphere geometry,you and your colleagues can't get enough of the astrological framework - "And wherever anyone would be, he would believe himself to be at the center.Therefore, merge these different imaginative pictures so that the center is the zenith and vice versa. Thereupon you will see-- through the intellect..that the world and its motion and shape cannot be apprehended. For [the world] will appear as a wheel in a wheel and a sphere in a sphere-- having its center and circumference nowhere. . . " Nicolas of Cusa Any reader looking on would somehow know just how expensive this 'fun' celestial sphere reasoning now is with no possibility of putting the brakes on the reckless conclusion of carbon dioxide and global warming by virtue of predictions but it something more fundamental than that.How is it possible that in the 21st century that a person can knowingly and without the expectation of any objection can discuss celestial sphere things as actual instead of the horror that it is ?.I am sure some know by now. I've got everything done save for a star field background. *Yes, I know you can't really see the stars if the lighted portion of Earth is also in-frame, but I want them anyway. *Artistic license and all that. Blender has a nifty utility that will generate a fairly good looking star field background, and I'll use that if I have to. *I'd rather have an accurate celestial sphere, though. For this to work, I need a rectangular image that I can coordinate transform onto a sphere. *In 3D modeling parlance, it's called UV mapping--because you coordinate transform Cartesian x and y coordinates into spherical coordinates u and v (with r assumed constant). *Think of it as a Mercator projection in reverse... although it's not exatly the same thing. Does anyone know of an image suitable for UV mapping onto a sphere that would generate an accurate celestial sphere? I suppose my only other realistic option would be to obtain a star catalog and write a Mathematica routine to grab all stars below magnitude m and project them on to a plane, then export the whole shebang as a honkin' big jpeg or PNG that Blender can then wrap onto a sphere. Any other ideas on how I might approach this? Thanks! -- Dave |
#5
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Celestial sphere image?
Dave Typinski wrote in
: I recently had the same need and I ran across the following: http://www.oera.net/How2/TextureMaps.htm That's great! Thank you! I like his Earth Texture Atmospherical, too... the colors look like they might actually work better than the one I got from this great place, which seems to specialize in super-high-resolution stuff: http://planetpixelemporium.com/earth.html Thanks for that link. I'll check it out. But then again, it may be good enough for your needs. Or perhaps I'm just being nitpicky. Not at all. It looks a bit dark, but some massaging with Photoshop oughtta bring things up a bit. Or not. Great resource either way. Now that you mention it, I also had to brighten up the image to make it more useable. Had to be careful, though, or I started seeing artifacts. I'd love to find a similar UV map at a resolution at 4 times that - 10000x5000. Or, figure out how to make one myself. Just wanted to mention I just found the following at 8192x4096. I found it using google's image search on "starmap" and 'extra large' settings. http://local.wasp.uwa.edu.au/~pbourk...ous/starfield/ The page references POVRay, which I happen to use. However, I am using another program for the animation I'm doing. But hey, UV mapping is the easy part, right? This is a good one for our purposes as the stars at the top and bottom edges are properly distorted for use in spherical mappings of cylinders. I also found this one, which is only 2880x1440 and unrealistic, but really cool looking. It's also NOT properly distorted. http://bb.nightskylive.net/asterisk/...hp?f=1&p=88466 http://www.geckzilla.com/apod/tycho_cyl_glow.png Then I found this nice big 10000x5000 image. It happens to be properly distorted, but it also has constellation lines. Some time in an image editor could clear that up, but it's probably not worth it since it's not much bigger than the first one above. http://www.johnhpanos.com/starcal.htm http://www.johnhpanos.com/skymap.jpg hmmm...this reminds me... I never did finish that animation project. It had a similar purpose, to debunk a 'theory'. Oh? What theory was that? Something to do with the Earth's axis tilting. I'm just an amateur self taught CGI artist so I got kinda stuck on a few things. But I have since acquired more tools so I should be able to get around my problems now. If I can't render it right the first time, I should be able to fix it in post production! Brian -- http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html Quake "predictions": http://www.skywise711.com/quakes/EQDB/index.html Sed quis custodiet ipsos Custodes? |
#6
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Celestial sphere image?
Skywise wrote:
Just wanted to mention I just found the following at 8192x4096. I found it using google's image search on "starmap" and 'extra large' settings. http://local.wasp.uwa.edu.au/~pbourk...ous/starfield/ The page references POVRay, which I happen to use. However, I am using another program for the animation I'm doing. But hey, UV mapping is the easy part, right? This is a good one for our purposes as the stars at the top and bottom edges are properly distorted for use in spherical mappings of cylinders. Yes they are, and thanks a million! I also found this one, which is only 2880x1440 and unrealistic, but really cool looking. It's also NOT properly distorted. http://bb.nightskylive.net/asterisk/...hp?f=1&p=88466 http://www.geckzilla.com/apod/tycho_cyl_glow.png There's undoubtedly a way--PS plugin or standalone app--to transform a "square" image like that into the warped/stretched format needed for UV wrapping, although I haven't yet tried to find one. Then I found this nice big 10000x5000 image. It happens to be properly distorted, but it also has constellation lines. Some time in an image editor could clear that up, but it's probably not worth it since it's not much bigger than the first one above. http://www.johnhpanos.com/starcal.htm http://www.johnhpanos.com/skymap.jpg Those lines aren't all that thick; it'd make for a nice background--depending on the intent of the project, of course. I emailed the author to find out more about how he got the cyclindrical projection by stitching together a bunch of smaller images. If and when that process becomes understandable, I'll post it here. hmmm...this reminds me... I never did finish that animation project. It had a similar purpose, to debunk a 'theory'. Oh? What theory was that? Something to do with the Earth's axis tilting. Seems we're doing the same thing. ;-) I'm just an amateur self taught CGI artist so I got kinda stuck on a few things. But I have since acquired more tools so I should be able to get around my problems now. If I can't render it right the first time, I should be able to fix it in post production! Or just re-render it--which, unfortuantely, takes a while. I'm not even a CGI artist, just self taught and stubborn enough to wade through it all. I'm doing four animations, each one is 312 seconds long at 60 fps. I'll then use Vegas to make the final composition. The down side is that I've 74,880 frames to render--and each one takes about 35 seconds on this dual core Opteron box. That's about a CPU-month of rendering out of Blender. -- Dave |
#7
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Celestial sphere image?
On May 11, 3:42*pm, Dave Typinski wrote:
Skywise wrote: Something to do with the Earth's axis tilting. Seems we're doing the same thing. *;-) How intelligent does a person need to be to see that extending the Earth's spherical geometry into the celestial arena via a calendar driven Ra/Dec convention and without any qualifiers whatsoever will produce a celestial sphere geometry ?. Whatever drives people to believe that daily rotation to a stationary celestial sphere does not retain the architecture of the apparent motion about Polaris I do not know, but using a celestial sphere to justify daily rotation has consequences which close to being a dishonorable to human intelligence as it is possible to get - http://www.youtube.com/watch?v=XTTDWhky9HY In order to retain daily rotation to a rotating celestial sphere as the reference for everything in the Universe and subsequently rotational orientation to Polaris,they had to introduce a wandering analemma Sun to blur the original distinction between daily rotation and its true reference - natural noon. Call it what you will,a nightmare or a crisis,the every-point-is-the- valid-center basis for the so-called 'big bang' is simply Flamsteed's horror come to life,don't take my word for it,try 600 years ago when they tried to discover the exact arguments for planetary dynamics to obviate the need for celestial sphere observations and conclusions drawn directly from these observations - "Suppose person A were on the earth somewhere below the north pole of the heavens and person B were at the north pole of the heavens. In that case, to A the pole would appear to be at the zenith, and A would believe himself to be at the center; to B the earth would appear to be at the zenith, and B would believe himself to be at the center. Thus, A's zenith would be B's center, and B's zenith would be A's And wherever anyone would be, he would believe himself to be at the center.Therefore, merge these different imaginative pictures so that the center is the zenith and vice versa. Thereupon you will see-- through the intellect..that the world and its motion and shape cannot be apprehended. For [the world] will appear as a wheel in a wheel and a sphere in a sphere-- having its center and circumference nowhere. . . " Nicolas of Cusa |
#8
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Celestial sphere image?
On May 11, 8:34*am, oriel36 wrote:
....don't take my word for it... ***************** Feckwit, I don't think that will be much of a problem... |
#9
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Celestial sphere image?
Dave Typinski wrote in
news Something to do with the Earth's axis tilting. Seems we're doing the same thing. ;-) Well then. Seems I'll have ot finish up my work and then we can compare notes. I'm not even a CGI artist, I should qualify that and say I use the term "artist" loosely. A more accurate description might be CGI simulation. just self taught and stubborn enough to wade through it all. I'm doing four animations, each one is 312 seconds long at 60 fps. I'll then use Vegas to make the final composition. The down side is that I've 74,880 frames to render--and each one takes about 35 seconds on this dual core Opteron box. That's about a CPU-month of rendering out of Blender. At what resolution? My goal is HDTV 1920x1080, which take about 30 or so seconds per frame, but I do test runs at much lower resolutions so it only takes me a few minutes to check a scene for results. But, that's on a Core2 duo 3Ghz. I also have a quad and when I'm ready for the final render I'll be doing a network render job. If you want long rendering times, do a full raytrace with caustics and index of refraction through complex glass objects. snooooooze Brian -- http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html Quake "predictions": http://www.skywise711.com/quakes/EQDB/index.html Sed quis custodiet ipsos Custodes? |
#10
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Celestial sphere image?
On May 10, 10:50*pm, oriel36 wrote:
How is it possible that in the 21st century that a person can knowingly and without the expectation of any objection can discuss celestial sphere things as actual instead of the horror that it is ?.I am sure some know by now ******************* And I am just as sure that you are just about the only person on the planet who thinks this way. It must be lonely at the top... very lonely... |
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