Slow Elevation layer performance in 3.2 compared to 2.8

[tobiashermes]

We are migrating a scene from osgEarth 2.8 to 3.2 and noticed a performance decrease with 3.2 (rex) while loading TMS elevation data. In 3.2 it always takes a moment until the data pops up. In 2.8 we had a smooth loading terrain.

For testing we created a very basic setup and there is no other data involved than the Elevation layer. The data comes from a local hard drive and was created with osgearth_conv.

Video:
https://user-images.githubusercontent.com/6120647/164713945-2dd236a7-7e5c-4326-8c58-2d9c6d1b8cbd.mp4

Earth files and debug log:
comp_28_32_test.zip

Any ideas how to achieve a similar performance as in 2.8 with the mp-engine?

In the 3.2 debug output there are a lot of Replaced -340282346638528859811704183484516925440.000000 with NO_DATA_VALUE lines. - Could this be a problem? Or maybe some configuration settings for the rex engine I am missing?

Thanks!

[tobiashermes]

If I switch off normal_maps computation I get a good performance with the rex-engine (comparable to 2.8 + mp-engine):

<options>
    <terrain normal_maps = "false"/>
...

Vice versa: Enabling normal maps in the mp-engine slows down loading performance (comparable to 3.3 with default rex-engine settings).

So if you migrate and experience a similar performance loss this could be one thing worth trying.

[gwaldron]

You can also try progressive mode:

<options>
    <terrain progressive="true"/>

Some people notice a perceived faster loading time with this on.

[tobiashermes]

Yes! In progressive mode it loads faster. Now the overall performance is comparable to our old scene. Thanks!

[nebsar]

How can I apply "terrain progressive = true" programmatically without an earth file?

[tobiashermes]

I haven't tried but it looks like you could use:

osgearth/src/osgEarth/TerrainOptions

Line 198 in 0f589e5

void setProgressive(const bool& value);

if you build your map like this:

osgearth/src/applications/osgearth_minimap/osgearth_minimap.cpp

Line 52 in 22fe32d

TerrainOptions terrainOptions;

[nebsar]

Ok. I think "mapNode->getTerrainOptions().setProgressive(true);" works. Thank you.

[liu-do-program]

why is it still invalid ?