No stars beyond 16308.35 ly's from Sol

[chris]

There are actually two other limitations in Celestia related to stellar distances . . .

First of all, the size of the root node of the octree structure used for fast visibility processing is 15000 light years. That's an easy value to change, but the bigger problem of floating point precision comes into play . . .

Single precision floating point numbers have 23 bits in the mantissa. This is a precision of about 1 in 8,000,000. At a distance of 80,000 light years, one 'step' is 1/100 light year. Celestia does some special handling of stars closer than one light year to the camera, but outside of that range, it's all single precision arithmetic. At such great distances from the Sun, nearby stars would jump as you moved by them . . . There are several solutions to this that I'm considering. I could simply increase the range for special handling, but this has performance implications. The performance problems could be offset by increasing the special-handling range as the camera's distance from the Sun increased. This isn't very general, but it would work reasonably well with the existing database, where the star density increases toward the origin. The real long-term solution is to allow multiple star databases, each referred to a different center. This is analgous to the way that solar systems are handled now, with the coordinate system for planets 'rezeroed' to the location of central star.

--Chris

[Larre]

I am an not really an expert at the Celestia source code, but I did download it from the Source Forge repository.

This Octree structure that I've been looking at had a lot of nodes, but I did not see the root node, but that's because, I've just been skimming over the code.

I really need to take a closer look at the octree.cpp file. If I find any bugs in it, I will let everyone know on this forum.

I can see where Chris is coming from on this topic. The best thing to do is to create many octree structural files for the many star databases that would be rendered in Celestia.

These should have a center, in the center of every galaxy. The larger octree files would need to be expanded in larger galaxies, while the current size is perfect for the smaller galaxies and globular clusters.

Keeping in mind that larger galaxies, like M31, also known as Andromeda, are over 50,000 ly in diameter. These galaxies may need more than one star database per galaxy to be rendered.

The other option would be creating and octree file for every star, and that would take a very long time, since there are billions of stars out there in space, and would slow Celestia down significantly..

Hope this helps..

Peace, Larre..

[Chuft-Captain]

The real long-term solution is to allow multiple star databases, each referred to a different center. This is analgous to the way that solar systems are handled now, with the coordinate system for planets 'rezeroed' to the location of central star.

Code: Select all

"Sol" "MilkyWay"
{
    Class "Star"

    OrbitFrame {
        TwoVector {
            Center "MilkyWay"
            Primary {
                Axis "x"
                RelativePosition { Target "MilkyWay" }
            }
            Secondary {
                Axis "y"
                RelativeVelocity { Target "MilkyWay" }
            }
        }
    }

}


[Reiko]

The real long-term solution is to allow multiple star databases, each referred to a different center. This is analgous to the way that solar systems are handled now, with the coordinate system for planets 'rezeroed' to the location of central star.

Code: Select all

"Sol" "MilkyWay"
{
    Class "Star"

    OrbitFrame {
        TwoVector {
            Center "MilkyWay"
            Primary {
                Axis "x"
                RelativePosition { Target "MilkyWay" }
            }
            Secondary {
                Axis "y"
                RelativeVelocity { Target "MilkyWay" }
            }
        }
    }

}


Does that work??

[selden]

Reiko,

No, it doesn't work. Yet.

ChuftCaptain is teasing us!

[Chuft-Captain]

Not so much teasing,... as making a (slightly less than serious) suggestion in a language that I knew that Chris would understand.

Sorry if I got your hopes up Reiko. (I apologize for my obfuscation....damn it, I've done it again! )

For the same suggestion in English, see: http://shatters.net/forum/viewtopic.php ... axy+motion

[Reiko]

There goes my plans to form an evil empire based in the large magellanic cloud.

[barcajunior]

I'm waiting for your evil empire.

[Hungry4info]

I'm waiting for your evil empire.

And you'll be waiting for a long... long time.

[Reiko]

I'm waiting for your evil empire.

Like Hungry4info said, you will be waiting for a long looong time.

[kukareka]

I have bought today new computer Quad 9300 with 8Gb Ram and 512 Ati, I work so quickly, in a shock!!! Before was Celeron 2400 with 1Gb Ram...

[Reiko]

Well I have an evil empire in the Large Magellanic Cloud but it takes a long time to load the STC and SSC files.