## [Stellarium-pubdevel] Level of comet detail

 [Stellarium-pubdevel] Level of comet detail From: Kristen Aw - 2012-04-30 18:28:13 Attachments: Message as HTML ```Hi,   I was just wondering about the level of detail in comet rendering that Stellarium wants. Currently, from afar, the comets are balls of light, and when zoomed into, are rotating spheres with some crater-map. I understand that the plasma tail comes out cone-shaped, and appears at 1.5 AU, the dust tail appears at about 3 AU, and the coma is visible when it passes Jupiter (5 AU). And that the brightness of the coma/ length of tail increases as the comet approaches the Sun.   So, from afar, a comet would have a coma and tails. But what about when they are zoomed into? I guess it would have an irregular potato shape like Hartley, but as it releases gas/dust, should we be able the material coming out from vents, as the nucleus rotates...?   And also, should we be able to calculate if the observer sees an antitail (due to parallax), and whether the dust tail is viewed head on (it would be seen as a fan on a plane) or directly from the side (it would be seen as a straight line)?   I'm not sure how feasible the above is, so I'm just asking.   Thanks```

 [Stellarium-pubdevel] Level of comet detail From: Kristen Aw - 2012-04-30 18:28:13 Attachments: Message as HTML ```Hi,   I was just wondering about the level of detail in comet rendering that Stellarium wants. Currently, from afar, the comets are balls of light, and when zoomed into, are rotating spheres with some crater-map. I understand that the plasma tail comes out cone-shaped, and appears at 1.5 AU, the dust tail appears at about 3 AU, and the coma is visible when it passes Jupiter (5 AU). And that the brightness of the coma/ length of tail increases as the comet approaches the Sun.   So, from afar, a comet would have a coma and tails. But what about when they are zoomed into? I guess it would have an irregular potato shape like Hartley, but as it releases gas/dust, should we be able the material coming out from vents, as the nucleus rotates...?   And also, should we be able to calculate if the observer sees an antitail (due to parallax), and whether the dust tail is viewed head on (it would be seen as a fan on a plane) or directly from the side (it would be seen as a straight line)?   I'm not sure how feasible the above is, so I'm just asking.   Thanks```
 Re: [Stellarium-pubdevel] Level of comet detail From: Reaves, Timothy - 2012-05-01 01:30:20 Attachments: Message as HTML ```As a general rule, as accurate as possible. As you zoom in, the tail would still be visible. For the boy itself, there are some OBJ files available for some of the more major comets. For ones where these are not available, perhaps there is a library of OBJ files that could be sleected from based on composition, or some-such. As for seeing venting, that would definitely be nice. For the other questions, 'yes'. :) On Mon, Apr 30, 2012 at 2:28 PM, Kristen Aw wrote: > Hi, > > I was just wondering about the level of detail in comet rendering that > Stellarium wants. Currently, from afar, the comets are balls of light, and > when zoomed into, are rotating spheres with some crater-map. I understand > that the plasma tail comes out cone-shaped, and appears at 1.5 AU, the dust > tail appears at about 3 AU, and the coma is visible when it passes Jupiter > (5 AU). And that the brightness of the coma/ length of tail increases as > the comet approaches the Sun. > > So, from afar, a comet would have a coma and tails. But what about when > they are zoomed into? I guess it would have an irregular potato shape like > Hartley, but as it releases gas/dust, should we be able the material coming > out from vents, as the nucleus rotates...? > > And also, should we be able to calculate if the observer sees an antitail > (due to parallax), and whether the dust tail is viewed head on (it would be > seen as a fan on a plane) or directly from the side (it would be seen as a > straight line)? > > I'm not sure how feasible the above is, so I'm just asking. > > Thanks > > > ------------------------------------------------------------------------------ > Live Security Virtual Conference > Exclusive live event will cover all the ways today's security and > threat landscape has changed and how IT managers can respond. Discussions > will include endpoint security, mobile security and the latest in malware > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > _______________________________________________ > Stellarium-pubdevel mailing list > Stellarium-pubdevel@... > https://lists.sourceforge.net/lists/listinfo/stellarium-pubdevel > > ```
 Re: [Stellarium-pubdevel] Level of comet detail From: Alexander Wolf - 2012-05-01 08:40:57 ```2012/5/1 Reaves, Timothy : > As a general rule, as accurate as possible. I'm agree but without fanatism! > As you zoom in, the tail would still be visible. For the boy itself, there > are some OBJ files available for some of the more major comets.  For ones > where these are not available, perhaps there is a library of OBJ files that > could be sleected from based on composition, or some-such.  As for seeing > venting, that would definitely be nice. This is task not for current problem. More, this task is complicated and we not must it for include for comet tails. -- With best regards, Alexander ```
 Re: [Stellarium-pubdevel] Level of comet detail From: Georg Zotti - 2012-05-01 19:48:28 ```Both tails are not cones, rather thin paraboloids, with the nucleus in focus. The gas tail (bluish) should point straight away from the sun, the dust tail lags behind a bit, so you need to find not only position but speed (vector), and use this to push the tail from the direct antisolar direction. Anti-tails should be visible then just from observer/viewing geometry. The textures for those parabolas may be animated to move away from the coma and thin out. also, the ice/dust/gas "particles" coming from the vents should be pushed away from the sun. HTH, G. On Di, 1.05.2012, 03:30, Reaves, Timothy wrote: > As a general rule, as accurate as possible. > > As you zoom in, the tail would still be visible. For the boy itself, there > are some OBJ files available for some of the more major comets. For ones > where these are not available, perhaps there is a library of OBJ files > that > could be sleected from based on composition, or some-such. As for seeing > venting, that would definitely be nice. > > For the other questions, 'yes'. :) > > > > On Mon, Apr 30, 2012 at 2:28 PM, Kristen Aw wrote: > >> Hi, >> >> I was just wondering about the level of detail in comet rendering that >> Stellarium wants. Currently, from afar, the comets are balls of light, >> and >> when zoomed into, are rotating spheres with some crater-map. I >> understand >> that the plasma tail comes out cone-shaped, and appears at 1.5 AU, the >> dust >> tail appears at about 3 AU, and the coma is visible when it passes >> Jupiter >> (5 AU). And that the brightness of the coma/ length of tail increases as >> the comet approaches the Sun. >> >> So, from afar, a comet would have a coma and tails. But what about when >> they are zoomed into? I guess it would have an irregular potato shape >> like >> Hartley, but as it releases gas/dust, should we be able the material >> coming >> out from vents, as the nucleus rotates...? >> >> And also, should we be able to calculate if the observer sees an >> antitail >> (due to parallax), and whether the dust tail is viewed head on (it would >> be >> seen as a fan on a plane) or directly from the side (it would be seen as >> a >> straight line)? >> >> I'm not sure how feasible the above is, so I'm just asking. >> >> Thanks >> >> >> ```
 Re: [Stellarium-pubdevel] Level of comet detail From: Alexander Wolf - 2012-05-01 08:53:47 ```2012/5/1 Kristen Aw : > So, from afar, a comet would have a coma and tails. But what about when they > are zoomed into? I guess it would have an irregular potato shape like > Hartley, but as it releases gas/dust, should we be able the material coming > out from vents, as the nucleus rotates...? So, you need (since some level of zoom) render coma like current implementation for switch to textures for solar system objects. You can use spheroid as generic shape of comet core because 1) not for all comets have models with their shape and 2) renderer of OBJ files not very simple task and not this feature not in Stellarium's core. > And also, should we be able to calculate if the observer sees an antitail > (due to parallax), and whether the dust tail is viewed head on (it would be > seen as a fan on a plane) or directly from the side (it would be seen as a > straight line)? Yes, it must be calculated. -- With best regards, Alexander ```
 Re: [Stellarium-pubdevel] Level of comet detail From: Bogdan Marinov - 2012-05-02 12:28:09 ```On Mon, Apr 30, 2012 at 9:28 PM, Kristen Aw wrote: > Hi, > > I was just wondering about the level of detail in comet rendering that > Stellarium wants. Currently, from afar, the comets are balls of light, and > when zoomed into, are rotating spheres with some crater-map. I understand > that the plasma tail comes out cone-shaped, and appears at 1.5 AU, the dust > tail appears at about 3 AU, and the coma is visible when it passes Jupiter > (5 AU). And that the brightness of the coma/ length of tail increases as the > comet approaches the Sun. > > So, from afar, a comet would have a coma and tails. But what about when they > are zoomed into? I guess it would have an irregular potato shape like > Hartley, but as it releases gas/dust, should we be able the material coming > out from vents, as the nucleus rotates...? Getting right the coma and the tails has top priority. Things like venting and the shape of the nucleus are a finishing touch. Remember, Stellarium is supposed to be simulating mainly what can be seen with naked eyes, binoculars or an amateur telescope. Direct observations of a core is in the league of Hubble, space probes and programs like Celestia. ;) There are two major user groups of Stellarium - educators (including planetariums) and amateur astronomers. Try imagining that you are in each group and think about what would you want simulated and how much control on it would you like. "Everything" is not an useful answer. :) Regards, Bogdan Marinov ```