Celestia Forums

Grant,

Another question for you...

I've just tried to use another 3ds model (Jestr's) for Amalthea. Just wanted to see what happened.

The whole locations MARKing and GOTOing functions got screwed. I rather expected this, but now I'm just curious. If someone wishes to make a model which WORKS with the new setup under Celestia 1.3.2 Pre1, then what are the requirments for the new 3ds model. Also, do the textures need some tweaking too?

I used the same Amalthea texture which now WORKS with your locations file and your Amalthea 3ds model, but the texture did NOT work with Jestr's model.

Can you set out the guidelines somewhere so that model makers everywhere will be AWARE of the new requirements?

Just another thought for you.

Take care, Bob

I was going to ask Grant,presumably all my moon models are the wrong way around for Celestia1.3.2pre1.I've corrected Phobos and Deimos and will start on the others today.

Bob Hegwood wrote:Can you set out the guidelines somewhere so that model makers everywhere will be AWARE of the new requirements?

It's on my list, Bob. But I'm a little hampered by the fact there doesn't seem to be any consistent terminology within even the small number of 3d editing tools I've used so far. In fact, it took me a long time to find a package that even did what I wanted in terms of rotating the model's coordinate system locally. Makes it difficult to describe the requirements to someone else using a different package.
And I've no desire to turn into the add-on police - a while back I briefly tried to explain that a particular model just wasn't aligned in a way that would allow it to behave properly in Celestia, but neither the author nor the users seemed at all interested. Some folk are just happy when things look nice, and after a bit of reflection I realised that that wasn't anything I should be interfering with.
But Jestr's keen to get his real-world models aligned nicely, and now that he has shifted to 1.3.2pre1 I'm happy to spend some time helping with that.

Grant

Bob ,I've just finished a correctly aligned version of Amalthea for Celestia 1.3.2 pre1 you can get it here
http://www.geocities.com/jestrjestr/extras
look for 'newamalthea.zip'.Hope this helps Jestr

Grant? Jestr?

Many thanks to you both for the information, and hopefully, an Amalthea model which is both functional within Celestia, and doesn't look so crappy. i.e. - The seams and lines on the current model tend to distract one from the real (beauty?) of the moon.

That's why I was trying to see if Jestr's model would suffice, the current Celestia model just has too many ugly features to be of much use.

I know, all I do is bitch... However, I have downloaded approximately four different 3d programs, and I intended to learn how to use them in order to repair/create models on my own.

Grant, are you SURE you can't outline the process for us somewhere? Would - hopefully - make the CORRECT information available to those who wish to contribute ACCURATE models to Celestia. Yes?

Thanks for the model, Mr. Jestr, sir...

I'll have a look at it shortly.

Take care, Bob

jestr wrote:Bob ,I've just finished a correctly aligned version of Amalthea for Celestia 1.3.2 pre1 you can get it here
http://www.geocities.com/jestrjestr/extras
look for 'newamalthea.zip'.Hope this helps Jestr

Mr. Jestr, sir...

The new model is EXTREMELY beautiful, and works flawlessly in terms of MARKing and GOTOing. Chris? Grant? Add this model to the distribution package willya?

I wasn't going to modify my Jupiter Tour anymore becuase I wanted to start working on Saturn.

However, I just HAVE TO add this model to the package. Again, it is beautiful work Jestr. No lines, no flaws... Just beautiful.

Thanks *very* much sir... I'll have it included with my Jupiter packages within the hour.

Take care, Bob

Jestr:
The texture of your Amalthea model is distorted - stretched at the poles and also around 90 and 270 degrees longitude. The problem is initially visible because some of the craters are stretched into ovals.
Try laying on the blank grid I sent you and using Goto Object to travel to a particular latitude and longitude (switch the marker on so that you can see where you end up). If you goto Latitude 30, Longitude -60, you'll find yourself above something like Latitude 35, Longitude -70 according to the applied texture. A visual comparison with the original model should make it clear this is a texture problem rather than anything else.
Another thing you may want to do is provide people with a MeshCenter setting to use with your model - this tells Celestia where the centre of the model should be, so that it rotates precisely on its axis and locations display at the exact latitude and longitude. The settings I give in solarsys.ssc are precise for the original models, but since you've changed the shape of the model while rebuilding it, you need new values. Does your modelling tool give you the coordinates of the mesh centre? If so, you just need to multiply each of those coordinates by -1 to get the MeshCenter settings for Celestia. I make the MeshCenter for your Amalthea model to be:

Grant

granthutchison wrote: Jestr:
The texture of your Amalthea model is distorted - stretched at the poles and also around 90 and 270 degrees longitude. Grant

If you don't mind my saying so, Grant, this model ain't NEARLY as distorted as the one which comes with Celestia. On THAT model, the lines which define the shape of the model are so clearly pronounced that you can't help but be distracted by them.

Of course, I don't know beans about the longitude, latitude, central mesh coordinates, etc...

All I know is that I now have a BEAUTIFUL model which does precisely what it should do within a script.

Love ya, Bob

Bob Hegwood wrote:If you don't mind my saying so, Grant, this model ain't NEARLY as distorted as the one which comes with Celestia.

Umm, Bob?
Didn't you go crazy a while back because the location labels weren't next to the features they labelled? If the texture isn't applied to the model properly, that's precisely what happens. Jestr's model has latitude and longitude errors of close to 20 degrees in places, which is more than enough, even in a lo-res place like Amalthea, to shift the features out from under the labels. You should compare the apparent position of Lyctos Facula in the original and in Jestr's new version. A similar distortion in, say, Phobos, would have labels sitting well outside the craters they marked.
I'm not trying to detract in any way from Jestr's work - but because I know he's keen to get things right, I'm pointing out the problems so the end result can be even better. It's just a matter of reapplying the texture in a spherical mapping.

Grant

Grant,

All I know is that the Pan and Gaea Craters were marked and located in the same positions that they were using the original model. Now, you may have a point with the Lyctos Facula because I couldn't even SEE that feature using the original model. Sheesh!

It *may* be that I'm also not seeing any discrepancy because of my poor, Open-GL limited machine and the maximum 1024 x 512 texture size available to me.

At any rate, I *still* think the new model looks better than the old one. I can actually SEE features other than the joint lines now.

Take care, Bob

Okay Grant,

Just so's we can SEE the differences, have a look at the following:

From ORIGINAL Celestia model...







From Jestr's BEAUTIFUL model...







You're correct *I think* about the positions being off a bit, but - honestly - I can't tell any difference except that the NEW model is prettier and easier to locate the features on.

Just thought I'd make sure you saw what I'm seeing here.

Honestly, I'm not trying to be a pain, I just thought that the new model was better for everyone. Keep in mind, however, that I'm no rocket scientist. When you start talking about latitudes, longitudes and central meshes, I'm a bit behind in the learning curve.

Hope this helps.

Take care, Bob

Bob Hegwood wrote:You're correct *I think* about the positions being off a bit, but - honestly - I can't tell any difference except that the NEW model is prettier and easier to locate the features on.

Compare the greenish-yellow area which just fills Gaea crater in the original, but spills out all across the south polar region in the new model; notice the green smear along the rim of Pan crater in the original, which is now beyond the crater rim in the new model - these are huge differences, Bob!

Bob Hegwood wrote:Honestly, I'm not trying to be a pain, I just thought that the new model was better for everyone.

It's a nice model, for sure - but right now it's inaccurate. Soon it'll be accurate, and it'll be even nicer. That's all I'm saying, Bob, and I'm sorry if that has upset you in some way - it surely wasn't intended to.

Grant

Grant,

Not upset in any way, except that now I'll have to wait some more for the perfect model.

Do you see what I meant about the lines on the original model though?

I guess that I was just so happy to these lines gone that I neglected to check out the rest of the scheme as well as I should have.

Please remember too, that I personally have *no* idea what the moon SHOULD look like. All I knew was that the features seemed to line up according to where they should have been.

You are correct in pointing out the differences in the green shading though. However, I really just did not know where the green was supposed to be, and that explains - hopefully - why I didn't see anything wrong.

Sorry about that. I'll try to be a bit more discerning in the future.

Take care, Bob

Bob Hegwood wrote:Do you see what I meant about the lines on the original model though?

Sure. They're a result of the small number of mesh faces, and the tight curvature of the surface in that region. You'll see them in several places with tight curvature - like the sharp ends of Eros and Ida. I think placing a few more vertices in those specific regions would sort (or reduce) the problem without having a runaway in file size.
But I also don't know nearly enough about how Celestia handles 3ds objects - I wonder if the visible seam and the corners are inevitable in these 3ds models, or if some manipulation of the normals calcs in Celestia could sort the problem without having to alter the models at all.

Grant

But THAT is what I was trying to point out in Jestr's model...

I've looked at it from every angle using Celestia, and there's not one line or crease in the images that I've seen. Doesn't this mean that the models just need to constructed differently?

Mr. Jestr? Any thoughts? How did YOU get rid of all the ugly lines and creases?

Thanks, Bob

PS - I sure know how to get a topic up and running don't I?

Bob Hegwood wrote:I've looked at it from every angle using Celestia, and there's not one line or crease in the images that I've seen. Doesn't this mean that the models just need to constructed differently?

Jestr has added a very large number of faces, which has increased his file size more than fourfold. But the extra faces mean that the curvature at any given crease is very small, so the normal smoothing functions within Celestia can hide the creases. Smoother model, bigger file.
What I suggested above is that we should be able to achieve the same effect by only increasing the face number where the curvature is so large it's causing visible defects - we leave the rest unchanged because it already looks smooth. Smoother model, marginally bigger file.
There's just the simple matter of implementing this Cunning Plan ...

Grant

Okay Grant,

Jestr was kind enough to correct the apparent problems with the Amalthea model and he's made another one available on his site. I've now included the new, corrected model with the JupiterTour COMPLETE package.

I know you're going to hate me for this, but I *still* liked the un-corrected version of the model better. Now, we have another crease running from the Gaea Crater towards the end of the moon.

Sorry Jestr, I am *not* suggesting that you work on it some more. I'm gonna have to learn how to create these models myself, and then *do* something about it.

Thanks *very* much to both of you for all of your hard work.

Take care, Bob