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URI's and filesystem access

Posted by Kimmi, in ZFX-Community-Engine 2, Realtime graphic, assimp 02 November 2011 · 567 views

  • first screen1

I finished the first approach to import assets in a separate loader task and I was able to see my first imported model. Currently any kind of texturing needs to be implemented. But how can you desribe the location of a resource like a texture or a shader in a elegant way?

So I added a class called Uri. This stands for unique resource identification ( see http://en.wikipedia....urce_Identifier to learn more about this ). This Uri is the new way to describe the place where you find your resources. For instance if you want to load a resource from your locale filesystem at
[source lang="cpp"][/size][/font][/size][/font][font="arial"][size="2"][font="arial, sans-serif"][size="2"]filename = "c:\models\spider.obj"[/size][/font][/size][/font][font="arial"][size="2"][font="arial, sans-serif"][size="2"][/source]

the URI format will be:

[source lang="cpp"]
uri = "file://c:/models/spider.obj" ( on a windows xp system )
[/source]

The interesting thing is the scheme of the URI ( here the attribute file:// ), which describes the type of filesystem we have to use to open this resource. I introduced a new class called IOServer, where you can get a filesystem instance to manage the requested file system. For instance if you have a URI like:
[source lang="cpp"][/size][/font][/size][/font][font="arial"][size="2"][font="arial, sans-serif"][size="2"]uri = "zip://texture.jpg";[/size][/font][/size][/font][font="arial"][size="2"][font="arial, sans-serif"][size="2"][/source]
You can get the mounted filesystem and get a stream to access the resource as following:
[source lang ="cpp"][/size][/font][/size][/font][font="arial"][size="2"][font="arial, sans-serif"][size="2"]Stream *pZipStream = NULL;[/size][/font][/size][/font][font="arial"][size="2"][font="arial, sans-serif"][size="2"]IFileSystem *pFS = IOServer::instance()->getFileSystem( "zip" );[/size][/font][/size][/font][font="arial"][size="2"][font="arial, sans-serif"][size="2"]if ( pFS )[/size][/font][font="arial, sans-serif"] [/font][/size][/font][font="arial"][size="2"][font="arial, sans-serif"][size="2"] pZipStream = pFS->open( uri, Stream::ReadAccess );[/size][/font][/size][/font][font="arial"][size="2"][font="arial, sans-serif"][size="2"][/source]

Currently I only have mounted the locale filesystem as the default one. If you want to use this you have to mount the zip-filesystem before:

[source lang="cpp"]
// Mount the zip file system.
IOServer::instance()->mountFileSystem( "zip", new ZipFileSystem( "c:\\archive.zip" );
...
// get the file system
IFileSystem *pFS = IOServer::instance()->getFileSystem( "zip" );
[/source]

I saw this approach first in the Nebula3 Device and I was amazed to see a really clean design for that kind of problems. Thanks guys!

But there is still some work to do. Currently you can only mount one Zip-Archive. If you want to switch to a different one you have to unmount the older one and remount the new. Here I want to be able to deal with multiple archives. But for a first proof of concept this should work. And I missed a simple search method as well. Currently you have to know where to look for your textures. And this is not comfortable in my eyes.





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