plib-devel

[Plib-devel] SSG: Using the bitmap loaders for own texture classes?

[Jan R. <slo...@gm...>]

Hello,

I'm planning to create my own ssgTexture classes, because I need
some special handling not covered by the standard ssgTextures:

- subdivision of large bitmaps (1536x1536 or 2048x2048) into
  small textures suitable for the given OpenGL implementation
- no mipmapping
- GL_CLAMP_TO_EDGE, if supported by the implementation,
  GL_CLAMP otherwise

Creating the texture class wouldn't be a problem, but I'd
like to use SSG's bitmap loaders to get access to all
supported file types at once. The only problem is that the
loader routines automatically call ssgMakeMipmaps() to create
the textures which is, in my situation, not applicable.

Wouldn't it be a useful extension to SSG if the loaders could
be accessed separately if someone only needs the raw pixels?
What do you think?

Kind regards,
Jan R.

-- 
Jan Reucker
email: jan dot reucker at web dot de
web:   http://www.reucker-online.de

Re: [Plib-devel] SSG: Using the bitmap loaders for own texture classes?

[<p.l...@ci...>]

You could approach by overriding the default createTexture() method in the
ssgLoaderOptions class, which is then used by almost all 3D loaders. To do
that:

class LoaderOpts_CustomCreateTextures : public ssgLoaderOptions
{
public:
  virtual void createTexture( char* tfname, int wrapu, int wrapv, int mipmap )
  {
    // fill it with your code
    // refer to the default ssgLoaderOptions::createTexture in ssgLoad.cxx
  }
}

LoaderOpts_CustomCreateTextures loader_opts;

ssgSetCurrentOptions( &loader_opts );

// all further calls to ssgLoad() will call
LoaderOpts_CustomCreateTextures:createTexture()

Greetings -

Paolo



Scrive Jan Reucker <slo...@gm...>:

> Hello,
>
> I'm planning to create my own ssgTexture classes, because I need
> some special handling not covered by the standard ssgTextures:
>
> - subdivision of large bitmaps (1536x1536 or 2048x2048) into
>   small textures suitable for the given OpenGL implementation
> - no mipmapping
> - GL_CLAMP_TO_EDGE, if supported by the implementation,
>   GL_CLAMP otherwise
>
> Creating the texture class wouldn't be a problem, but I'd
> like to use SSG's bitmap loaders to get access to all
> supported file types at once. The only problem is that the
> loader routines automatically call ssgMakeMipmaps() to create
> the textures which is, in my situation, not applicable.
>
> Wouldn't it be a useful extension to SSG if the loaders could
> be accessed separately if someone only needs the raw pixels?
> What do you think?
>
> Kind regards,
> Jan R.
>
> --
> Jan Reucker
> email: jan dot reucker at web dot de
> web:   http://www.reucker-online.de
>
>
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>

Re: [Plib-devel] SSG: Using the bitmap loaders for own texture classes?

[Jan R. <slo...@gm...>]

Am Fri, 12 Aug 2005 16:36:43 +0200 schrieb p.l...@ci...:

> You could approach by overriding the default createTexture() method in the
> ssgLoaderOptions class, which is then used by almost all 3D loaders.

Hello Paolo,

thanks for your reply, but I think we're talking about different things.
My problem is the texture bitmap loading (loading a texture file into
memory so that I can access the pixel data), not the texture generation
itself. 

SSG encapsulates all those steps:

- allocate a texture handle
- call a loader function that matches the file extension
- the loader reads the pixel data into memory
- the loader function itself calls ssgMakeMipmaps() on the pixel data
  array for the actual texture generation

What I need:

- call the loader function directly
- manipulate the pixel data (split image into several tiles)
- generate textures from the tiles
- set the texture parameters the way I need them

Only step one is a problem, because I can't use the loader without
automatically invoking ssgMakeMipMaps. The rest is relatively easy.

Kind regards,
Jan R.

-- 
Jan Reucker
email: jan dot reucker at web dot de
web:   http://www.reucker-online.de