[osg-users] Custom code in OSG core

Sukender suky0001 at free.fr
Wed Nov 25 14:26:53 PST 2009


Hi Robert and Paul,

Oh, I'm sorry I shouldn't have written "core OSG": it's maybe more in osg plugins I guess...
I have to load huge models. By huge I mean a few thouthands triangles but GB of textures. Of course loading such a model simply leads to a std::bad_alloc. This is why I posted something about lazy textures/images on the mailing list: I must load the model but I don't want all the textures to be loaded at the same time. Depending on what I want to acheive I may need:
1. To leave textures unloaded, but I want writers plugins to do as if the texture was loaded (= the writer simply says "the texture is abcd.jpg").
2. To load low-res textures (or maybe not loaded at all), but I want hi-res ones to be switched when needed, especially when writing.

I don't expect solutions to be suited for "realtime" rendering. I only need those huge models to be loaded, then processed (= modifiy geometry without touching the texture or vice-versa, modify only a part of the scene...) and written to disk for future rendering.

I got a few ideas for these needs:
- Add a "noTexture" option to readers that stores somewhere the path of the texture file, and add an option to writers to do "as if" the texture was loaded (but only write to the file the path of the image). This is why I have custom code in reader/writers. But this is clearly an ugly solution as I need to modify each reader/writer.
- Create a "lazy image", which is loaded only when accessing pixel data. But I don't know if it's easy, and how to do it (as discussed in the corresponding post).

And a final note: all my code is given to osg-submissions once stable... I won't violate the OSGPL/LGPL :)

So... any idea? If I can acheive this without modifying OSG source code, then I'd be very happpy...

Thank you.

Sukender
PVLE - Lightweight cross-platform game engine - http://pvle.sourceforge.net/

----- Robert Osfield <robert.osfield at gmail.com> a écrit :
> Hi Sukender,
> 
> On Wed, Nov 25, 2009 at 2:26 PM, Sukender <suky0001 at free.fr> wrote:
> > I'm trying to add custom code in some osg plugins (especially 3DS and FBX). I often have to write things like:
> > ADD_DEFINITIONS(-DMY_CUSTOM_CODE) in CMakeLists.txt (or #define MY_CUSTOM_CODE)
> >
> > #ifdef MY_CUSTOM_CODE
> > ...
> > #endif
> >
> > - Can I submit such code (without the #define of course)?
> > - Do you think there could be a nicer way to isolate custom code?
> > - And finally, do you think this could be a good idea to have a CMake option such as "USER_DEFINES"? And then:
> > FOREACH(CUR_DEFINE ${USER_DEFINES})
> >    ADD_DEFINITIONS(-D${CUR_DEFINE})
> > ENDFOREACH()
> 
> The OSG isn't the place for custom code, both for a licensing issues,
> build issues and maintenance issues.  The question really should be
> how to avoid need for custom code in the core OSG.  The use of custom
> code embedded in the OSG code would suggest that the OSG doesn't
> support particular features, or isn't extensible enough, or just the
> that code is tackled in the wrong way.
> 
> Could you enumerate what custom code you are wanting to put it and
> why?  Perhaps we can figure a way to avoid the need for it completely.
> 
> Robert.
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> osg-users at lists.openscenegraph.org
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