[osg-users] osgEarth Feature multiple draw

[Michele Onnis]

Hi,

I'm using the osgEarth library and I'm trying to draw Time Space Position Information datasets with a playback functionality. I want to draw the whole trajectory and then draw a subrange of the SAME trajectory, with a different style, for playback purposes: the playback subrange is "translated" over time to achieve the animation playback.

In the first approach, I used two different node graphs based on osgEarth::Feature classes (Feature / Session / FeatureSource / FeatureModelGraph). I wanted to share the feature and specify two different draws of same feature (total range and partial range), but I could not find a way to do this. So, at every frame I add geometry to the playback feature and this action drops the framerate.

To solve the problem, I've tried to switch to a "lower level" implementation based on osg::Geometry. In this case, I share the vertex array between the whole trajectory and the playback trajectory, then I specified two DrawArrays with different ranges for the different renders. The performance of this solution is perfect, but the geometry shows jitter problems related to the single precision of the GPU (geometry is specified in world coordinates).

I know that in the second scenario I have to "localize" the geometry in a local origin to minimize the jitter, but I ask if there is a way to achieve the same results with the "higher level" approach (osgEarth::Feature classes), because I'd rather take advantage of all optimizations in this classes. So, how can I specify a single Feature and then specify multiple renders of the same Feature, with different ranges of the data and different styles?

Thank you!

Cheers,
Michele

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