[osg-users] osg::Cylinder height change not shown in OSG 3.6.3

Robert Osfield robert.osfield at gmail.com
Tue Nov 27 00:32:00 PST 2018

Hi Stuart,

The new ShapeDrawable is written completely differently, and is now
subclassed from osg::Geometry and has ShapeDrawable::build() function that
computes all the appropriate vertex arrays etc,  So try just calling
shapedrawabl->build() when you update the shape.

I should however suggest that perhaps ShapeDrawable isn't the tool for the
job for this type of interactive updating, it's written as a create once,
use many times features.  If you are updating the height interactively then
it may be best to just use a shader to set the height within the vertex
shader.  For instance if you had a 1000 cyclinders that all had
independently varying heights then I'd write this as an instanced geometry
with a uniform arrays or 1D texture that stores the position and sizes then
have the vertex shader positing and scale the geometry accordingly.  This
way you'd just update the uniform/1D texture in a super lightweigth way and
everything would just render smoothly and efficiently.


On Mon, 26 Nov 2018 at 21:55, Stuart Mentzer <osgforum at tevs.eu> wrote:

> Hi,
> I have an osg::Cylinder in an osg::ShapeDrawable and I change its height
> in an UpdateCallback like this:
> Code:
> cylinder->setHeight( h );
> drawable->dirtyDisplayList();
> drawable->dirtyBound();
> This works in OSG 3.4.1 but with OSG 3.6.3 (at least on my Windows builds)
> the height change doesn't show up. Checking the value with getHeight shows
> that the cylinder height is updated so maybe the issue is that
> dirtyDisplayList is no longer sufficient to trigger the display update.
> I can try to put together a small self-contained example if this doesn't
> give anyone a clue what is going on.
> Any help will be much appreciated. And if this has exposed an OSG bug it
> would be good to fix for 3.6.4.
> Thanks!
> Cheers,
> Stuart
> ------------------
> Read this topic online here:
> http://forum.openscenegraph.org/viewtopic.php?p=75246#75246
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