[osg-users] Custom code in OSG core

Robert Osfield robert.osfield at gmail.com
Thu Nov 26 01:41:25 PST 2009


Hi Sukender,

So what you are after is a proxy Image class :-)

One possible tweak would be to enable th OSG to carry osg::Image which
have their FileName field set, but have their data set to null so they
contain no data.  This is the easy part as you can do this right now -
the next bit is getting the OSG to handle these osg::Image objects
gracefully.

The issue of proxy image is something that the osg::Texture's
UnrefImageAfterApply could do with as it currently discards the whole
osg::Image, so later on when you try to save the model there is no
Image to provide the FileName to use to write to file you want to
write out.

So... this type of feature I can see having multiple uses beyond this
particular plugin and worthy of support into the core OSG.

Robert.

On Wed, Nov 25, 2009 at 10:26 PM, Sukender <suky0001 at free.fr> wrote:
> 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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>
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