[osg-users] questions about developing drivers for osg/osgEarth

speterson at idealaero.com speterson at idealaero.com
Mon Sep 23 12:37:22 PDT 2019

I took a step back and trying to figure this out using OGRFeature and osgEarth::Symbology::Geometry, I have no problem drawing shapes like I want and filling them in with color using the osgEarth::Symbology::Stlye etc.  But for the life of me can’t figure out how to apply my shader logic to my filled in geometry.  Every example I find online show osg::Geometry working with setOrCreateStateSet but I cannot find any such similar method in osgEarth::Symbology::Geometry.  I have tried to cast the osgEarth::Symbology::Geometry to osg::Geometry but that does not work.

I have gotten to this point before, before I went with the route I posted last week.  This leads me to dumping static geometry to the earth only, I don’t know how to work with the geometry to get it to do anything after displaying it on a layer.  I try to reset the size of the geometry etc via a thread with a loop in it but nothing changes.  I can remove the layer and add a layer but eventually same thing causes a crash, the same errors as before.

I am still stuck here trying to build a way to add an image to a layer, apply a shader to that image, and every once in a while change the image.  I am not making any progress alone here every approach I take leads to something that does not work for me.  I apparently am missing something that needs to be shared by someone to progress farther, I can’t find anything online that leads me to a solution of what I am trying to achieve.

Any help with code bits on what I am doing wrong is helpful, just saying stuff like: apply your layer update here doesn’t help that’s what I don’t know how to do.   Apply shader to your geometry doesn’t help that’s what I don’t know how to do.

I can apply shaders to textures just fine, I can apply shaders to images I place onto and image layer just fine.  I can’t figure out how update the layer without crashing and can’t figure out how to use osgEarth::Symbology::Geomerty with shaders or be able to update its position at all on the layer without removing and adding the layer again which eventually crashes osgEarth.

Thanks once again to anyone that can help.

From: osg-users [mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of Chris Hanson
Sent: Thursday, September 19, 2019 10:29 AM
To: OpenSceneGraph Users <osg-users at lists.openscenegraph.org>
Subject: Re: [osg-users] questions about developing drivers for osg/osgEarth

Ok. That helps a lot. Thanks.

So, I theorize that you are loading a 2d vector field as a data layer, that represents the 2D wind velocity vector at every data grid point covering the area, and then you use some kind of shader to display that as a colorfield and displays the moving flow lines? And then you update the 2d vector map periodically to represent the current data?

If that's the case, it sounds like you're just needing to load a conventional two-channel 2D image and do all the display work in shaders. That doesn't sound like how you're doing it though?

There's nothing at all that is file-specific about osgEarth, its drivers or its data sources. Many of the drivers talk to network-based data sources without accessing local files, so those shouldn't be an issue.

Glenn can probably comment better on how to best make a driver that updates itself periodically or on cue, but you ought to be able to just poll every 30 seconds or so and see if a data is available and refresh it somehow.

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