[osg-users] Global draw callback

Robert Osfield robert.osfield at gmail.com
Tue May 26 10:29:35 PDT 2015

Hi Farshid,

Added a if call on an inner loop of the draw dispatch traversal just for
the purpose of niche debugging isn't something I feel is justifying as
there will be CPU cost for everyone, even though very few people will use
that feature.

This type of customization would be better done via a custom RenderBin that
overrides the RenderBin::drawImplementation(..); This way only those who
need this customization would pay the extra cost of it.


On 26 May 2015 at 18:24, Farshid Lashkari <flashk at gmail.com> wrote:

> Hi Robert,
> I've run into the situation multiple times where having a global draw
> callback would have been very convenient. It's mostly been for debugging
> scenarios, but I can also see other situations where being able to globally
> augment draw calls would also be useful.
> What are your thoughts on having a global draw callback part of the
> osg::State object? It doesn't seem like much code would need to be changed,
> and the performance impact should be minimal.
> Essentially, osgUtil::RenderLeaf would be modified to call:
> state.draw(_drawable, renderInfo);
> And osg::State::draw would look like:
> if(_drawCallback.valid()) _drawCallback->draw(_drawable, renderInfo);
> else _drawable->draw(renderInfo);
> Does this seem like a reasonable feature to add? I can work on a patch if
> you feel it's appropriate.
> Cheers,
> Farshid
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> osg-users at lists.openscenegraph.org
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