Distance to object

Description: General discussion about Celestia that doesn't fit into other forums.

zeugma
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zeugma
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#1by zeugma » 07.01.2017, 21:47

I am not sure if this is the correct place to put this, so please accept my apologies if it should be somewhere else.

I'd like to make a feature request that I think might be fairly easy to implement. Currently, the "?" key reports the distance to a given object at the speed of light. While this is a cool and useful metric, I think an additional option might be useful. What I'd like to see is the ability to display how long it would take you to reach a given object at your current speed towards it.

One of the really cool features of Celestia in my opinion is that it is a great tool for showing someone how incredibly vast the distances are in space. I'd really like to be able to show someone how far it would take you to reach some objects, be the solar or extra-solar at speeds other than just C, especially given that the actual science we know of indicates that even reaching that speed would be incredibly difficult, if not impossible. I'm thinking that implementation would be fairly straightforward, especially since the calculation at C is already available. You could take your current 'velocity' and express it as a percentage of C and divide the current time at C, then express the result as a time measurement. What is cool about this,is that the equation would work both at subluminal and superluminal speeds. If you're 'travelling' at, say 10,000 k/s, the time reported would be much greater, and if you're travelling at, say 1 AU/sec, it would be shorter. Obviously, the case of "0" speed would be a special case, handled most likely by reporting the distance at C.

Obviously, given the limitations of the software, the calculation would be essentially a best case scenario, as it wouldn't take into account any subsequent movement of the object.

One of the real benefits of this, is that it would make Celestia even better as an educational tool than it already is.

I'd like to agree with what I have seen in earlier posts about 64-bit compatibility being more important than new features, but this is something that I think should be looked at once you start focusing on enhancements.

BTW, It is fantastic that Celestia is under development again. Any efforts to keep this program going is a great thing in my opinion, and I thank everyone taking part for your efforts.

John Van Vliet
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#2by John Van Vliet » 08.01.2017, 06:36

64-bit compatibility

basically a Microsoft only issue
except for ram use, the 32 bit 4 gig max, but getting it to use even 3 gig is a bit hard

as to
display how long it would take you to reach a given object at your current speed towards it.
that could be done using lua
and might be in a old "spaceship" add on


you have seen the Educational Activities plugins for MS windows ED version
http://celestiamotherlode.net/catalog/educational.php

john71
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#3by john71 » 08.01.2017, 07:57

KInda offtopic (sorry): 32 bit Celestia under Windows 10 64 bit is always crashing after loading too many textures. This is annoying and severely limiting the use of the program. On the other hand the new GAIA star data would need approximately 20GB star.dat to work, so in my opinion RAM usage and 64 bit compatibility are
very important...

zeugma
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#4by zeugma » 08.01.2017, 16:13

basically a Microsoft only issue
except for ram use, the 32 bit 4 gig max, but getting it to use even 3 gig is a bit hard

I think I was unclear in my original post. I think I said "64-bit compatibility" when what I was really talking about was a desire to see a native 64-bit version of the program. To me, that would make it run even better on more modern computers. I'm pretty much linux only on my personal hardware. One of the things I like about celestia is that it works well on Linux, OSX, and MS-Windows.

John Van Vliet
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#5by John Van Vliet » 08.01.2017, 18:39

builds just fine on OpenSUSE 42.2 using gcc 4.8 ( x86_64 )

using a 64 bit qt4 ,and 64 bit lua and png
this just leaves the ram limit mostly


as to the other crashing on win10 from " loading too many textures."

i suspect that is a win 10 caused issue and or a 3d card/chip driver issue

john71
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#6by john71 » 08.01.2017, 18:55

I don't think it is a Windows 10 or graphic card/driver problem, because no other graphic 3d software produced this kind of problem, including Space Engine which uses 128k textures...

I can use Gimp to edit 32k texture files in the GB data range with no crashes.

It can only be the problem of the Windows version of Celestia.

It is kind of ridiculous that 20-40MB dds files are crashing a PC with 8GB RAM and 8GB graphic card...

John Van Vliet
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#7by John Van Vliet » 08.01.2017, 19:20

if i load my earth
64k texture
64k normal
64k night
64k spec
32k cloud

the virtual textures , use only 700 meg of ram
and almost 1 gig if time is speed up 1000 X

if dds images are causing a issue
look at the Microsoft driver these are Microsoft direct X images

john71
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#8by john71 » 08.01.2017, 19:27

Png texture produces the same problem. One 8k planet means that I load 8k 20mb dds surface texture + 8k specular texture + 8k 40mb png bump map texture.

After 5-6 planets (or maybe more) Celestia first cannot load some part of the new surface texture of a new planet and after that it crashes...

Added after 4 minutes 42 seconds:
"Cannot load some part of the new surface texture" means the planet is without surface texture and looks dark...

Added after 9 minutes 4 seconds:
John Van Vliet: please go to 350km from the Earth (64k) surface and look around with your mouse. The 32k clouds need time to fully load. After this please go to an other hires planet, look around as I described it and then go to another hires planet. Celestia crashes after a few planets (on my PC anyway).

selden
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#9by selden » 09.01.2017, 10:29

john71,

What is your computer's hardware configuration? What type of CPU? How much RAM? What graphics hardware? How much graphics memory? How big is its paging file?

Occupying all of the available graphics or main memory often will cause problems like what you describe. Celestia never frees up any graphics or main memory that has been occupied by surface textures.

You can use a utility like GPUShark to determine how much graphics memory is being used, while TaskManager displays main memory usage.
Selden

john71
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#10by john71 » 09.01.2017, 21:13

selden, thanks for your reply.

Intel Core i5 8GB RAM + AMD Radeon HD 7700 8GB.

Paging file is 3456 MB.

Celestia is crashing for example at 1437MB RAM. RAM data is building very slowly (with maybe 30s-1 minute "screen freezes"), but CPU usage is never above 50%.

selden
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#11by selden » 09.01.2017, 22:13

Crashing at 1.4 GB doesn't sound too unreasonable, although I would have expected it to get closer to 2GB. Have you applied the 4GB patch?
See http://www.ntcore.com/4gb_patch.php

CPU usage of 50% suggests to me that you have a dual core I5 and one of the cores is saturated. Celestia is single-threaded, so In almost all cases, it'll use 1 core all of the time (unless it's minimized to the taskbar). Celestia won't update its screen (i.e. it seems to hang) during the time that it's loading a file. File loading will take less time if you use an SSD (solid state disk) instead of an HDD (hard disk drive = "spinning rust").
Selden

john71
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#12by john71 » 10.01.2017, 17:39

Whoa, the patch is good, Celestia crashed approximately at 2000MB RAM, but it went to 2100MB at one point before the crash. By the way, is it possible to have a "Loading..." sign on the screen during the RAM loading? It would be nice...
Also RAM usage should be on the screen too, it would be a nice way to know the limits of Celestia before it crashes...

Added after 9 minutes 26 seconds:
Started a new topic: http://celestiaproject.net/forum/viewtopic.php?f=10&t=17592

selden
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#13by selden » 11.01.2017, 11:15

When using a Cel or CelX script, it's easy for the script to display a "loading" message just before it references an object and starts loading.
Selden


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