Celestia Forums

In the ChangeLog from celestia cvs I found this new entry:

Implemented virtual textures, for ultra-high resolution texture mapping of planets.

This definitely sounds interesting, but what does that mean and how can we use it? Please excuse me if that feature was announced on forum before, but I could not find anything relevant by searching it and I have been away for about a week.

steffens

See: http://ennui.shatters.net/forum/viewtopic.php?t=3041
for Chris's initial post about this.

i think he wanted a simplified version of it, and i know i would too, what a headache it was to read through it.

Hmmmm, well, if _I_ understand it correctly, and if I don't I'm sure someone will correct me ...

As you get closer to an object, Virtual Textures will allow the texture of the object to change automatically, "on-the-fly", by Celestia (if you have some installed) to a texture with more detail in it. For example, when you hit the zoom-in button, a better texture will be loaded for your new, closer altitude.

Someone could create a set of virtual textures for the Niagra Falls area. Then, when loaded, a user might see texture 1 at 1000 km altitude, texture 2 at 500 km, etc. Virtual Textures can also be "tiled", like a checker board -- with other textures of the same "clarity" to the left, right, up, and down (all horizontal) to the one you are currently viewing. Sounds like it's gonna be a LOT of work to put together a multi-altitude virtual texture!

This new feature is going to be driven solely by the folks who create textures, and it may take a while before everything is working just right, from everyone's perspective (texture creators, developers, users, etc.). It's gonna be beautiful to see some of the creations folks come up with!

As I understand it:

Currently in Celestia, a single texture file must cover the entire surface of the planet. The full texture file has to be loaded, even if only part of the surface is visible, or if the surface is being viewed at a distance where the full resolution is not needed. This takes time and texture memory.

Virtual textures allow the texture to be divided into multiple pieces (tiles), each of which covers only a part of the surface. Also, tiles are defined at multiple levels of resolution. Instead of loading a single high-resolution texture for the entire surface, Celestia need only load the tiles for the part of the surface which is currently visible, at the resolution appropriate for the current viewing distance.

This approach should significantly reduce the time required for texture loading and also reduce the texture memory requirements, so that large textures can be used on more systems. Celestia should no longer come to a halt as you approach a planet with a high resolution texture.

In addition, it will be possible to define extremely (arbitrarily) high resolution textures, limited only by available disk space and data sources. This is likely to be available only for limited areas. In my opinion, while this should be a lot of fun, it is a secondary benefit. The main benefit is in making large (e.g. 32K) whole planet textures more usable.

- Hank

Ahhhh, now THAT makes good sense!

Thank you Hank.

billybob884 wrote:i think he wanted a simplified version of it, and i know i would too, what a headache it was to read through it.

Well, if you look closely at the timestamp of my post, then you will know that i wrote it before chris anounced his new feature.
Now I'm happy to see that this feature is really what I hoped it to be - a chance for my quite old computer to render hires planets...

steffens

steffens wrote:Well, if you look closely at the timestamp of my post, then you will know that i wrote it before chris anounced his new feature.

No you did not.

YAY! Now we can zoom to see the high res version of the face on mars!

marc wrote:

steffens wrote:Well, if you look closely at the timestamp of my post, then you will know that i wrote it before chris anounced his new feature.

No you did not.

Yeah he did, Chris's post was around 11:20 AM, and his post was around 10 AM on the same day.