Comet's coma

[ElChristou]

I have a problem with comets since yesterday build. Coronas are not displayed anymore. Someone can confirm?

[chris]

I have a problem with comets since yesterday build. Coronas are not displayed anymore. Someone can confirm?

I'm still seeing comet tails.

--Chris

[ajtribick]

I'm still seeing comet tails.

Me too.

[selden]

I just now downloaded 4455 and rebuilt it from scratch.
Comets still look the same as before.
When I set the date to 9 Feb 1986, Halley has both a coma and a tail, and Hale-Bopp has a coma (although it really shouldn't at 20 AU from the Sun).

Make sure you have comets enabled.

[ElChristou]

I see the tails but not the coronas... I'll try a new build to see...

[selden]

I think you mean "coma" not "corona".
The coma of a comet is the brightest part closest to the comet.
The corona is the outer layer of the Sun, visible during an eclipse.

[ElChristou]

Yep, sorry Selden. Here is what I have with a 2 minutes ago build:

bor.jpg

No coma at all...
How can I debug this?

[chris]

Yep, sorry Selden. Here is what I have with a 2 minutes ago build:

No coma at all...
How can I debug this?

Can you provide a cel URL?

--Chris

[ElChristou]

Can you provide a cel URL?

I have no comas at all whatever comet I visit. Anyway, here is one:

cel://Follow/Sol:Borrelly/2008-09-22T20 ... 2306&ver=2

[selden]

That url looks (almost) OK under Windows XP when running Celestia r4460.
It does have a dark region between the coma and the tail, but the coma is being drawn.

You might try deleting all of the .h and .cpp files and doing an svn update to make sure you have all of the correct files, then rebuild. Otherwise, it might be a Mac graphics driver problem

[t00fri]

Yep, sorry Selden. Here is what I have with a 2 minutes ago build:

bor.jpg

No coma at all...
How can I debug this?

Nope. everything fine under Celestia-KDE (build 4450)

Fridger

[ElChristou]

You might try deleting all of the .h and .cpp files and doing an svn update to make sure you have all of the correct files, then rebuild. Otherwise, it might be a Mac graphics driver problem

I'll try that...

[ElChristou]

Nope, I delete all src and update my source, same thing.
Must be something with the Xcode project, but I think I will wait the next changes by DW to rebuild with a fresh Xcode file...

[t00fri]

Christophe,

how about correcting the misleading title of your thread: corona -> coma?

Fridger

[Cham]

I don't have any problems with comets.

[chris]

Reposting from the dev list:

Here's a patch (and replacement render.cpp) that should fix the comet bug reported by Christophe:

http://www.celestiaproject.net/~claurel/celest ... /cometbug/

The calculation of comet tail normals was incorrect--for the front of the comet tail, it was taking the square root of a negative value. Eventually, a negative infinity was passed to the graphics hardware. The floating point units on all but the most recent graphics hardware is not IEEE754 compliant, so the handling of infinities and NaNs is essentially unpredictable. That's why the bug appeared on Christophe's system, but not on anyone elses.

The patched code also fixes the problem where the comet's coma was being rendered regardless of the distance from the Sun. The rather odd looking bright 'cap' is also gone.

--Chris

[ElChristou]

Reposting from the dev list:

Here's a patch (and replacement render.cpp) that should fix the comet bug reported by Christophe:

http://www.celestiaproject.net/~claurel/celest ... /cometbug/

The calculation of comet tail normals was incorrect--for the front of the comet tail, it was taking the square root of a negative value. Eventually, a negative infinity was passed to the graphics hardware. The floating point units on all but the most recent graphics hardware is not IEEE754 compliant, so the handling of infinities and NaNs is essentially unpredictable. That's why the bug appeared on Christophe's system, but not on anyone elses.

The patched code also fixes the problem where the comet's coma was being rendered regardless of the distance from the Sun. The rather odd looking bright 'cap' is also gone.

Do you mean Selden's previous image with the bright cap wasn't a wanted effect?
I've build upon 4466 and do have the coma, but it react now as the rest of the tail in transparency or brightness. The coma itself alone is no more visible... (is that what you wanted?)

[Dentarthurdent]

Where do the patch and replacement render.cpp files go? I've had this same problem with comets and their comas. Much appreciated.

[selden]

Dentarthurdent,

You need to build Celestia from scratch. It's not a patch that can be applied to v1.5.1. This bug is fixed in the current SVN revision of Celestia. I don't know if anyone is still providing a pre-compiled copy of that revision. For what it's worth, I'm feeling optimistic about the availability of v1.6. If things go well, a "release candidate" might be available within the next month or so.

There are notes elsewhere on this Forum and in the Celestia Wikibook describing how to get started compiling Celestia. http://en.wikibooks.org/wiki/Celestia#Development