Jul 22 2008

OpenSim – First LiDAR reflective DEM sculpties placed

OK, not everyone in the immersive modeling universe has been holding their breath on this one, but hey, I’m happy to say that the production line is fired up and creating 2560 sculptie bumpmaps to inflate the Open Berkurodam sim using LiDAR reflective digital elevation model (DEM). The registration with orthoimagery is not perfect, and small offsets are very distracting, but the first two have been placed, and should illustrate the concept. (Two rezzed, 2558 to go…)

Sather Tower as two reflective digital elevation model sculpties

The reflective DEM sculpties have 16 times greater resolution (that’s resolution as NURB point density) than the underlying terrain megaprims. This means that for the 40-region Open Berkurodam sim, there are 160 terrain megaprims, and 160 tiles of 10-cm orthoimagery. The reflective DEM sculpties number 2560 and will be textured using the same orthoimagery.

Reflective DEM surfaces ride over the tops of trees, rooftops, or any structure. They are defined by the first return of the LiDAR reflected signal. By contrast, the terrain megaprims are based on a model of the last return (in these data up to the seventh return signal) that represents the ground under and around all structures and trees.

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Apr 29 2008

Megaprim terrain ’til the cows come home

Published by under BART Station,OpenSim,Scale Issues

There has been a bit of head scratching as other distractions apparently clouded an obvious scale issue. The first terrain megaprim sculptie project done last month, had available imagery at 30cm.  For that, it only made sense to oversample to 25cm to make 512×512 textures.  That decision led to my adding a collar around the original 512’s until they clicked into the proper size without rescaling on a quarter-region megaprim. With Berkeley, the source imagery is almost 10cm (103mm pixels) and the challenge has been to size the resample so as to make best use of the 1024×1024 texture size limit per prim.

Where I took a wrong turn was trying to proportion the collar that was added to the 512’s, rather than going back to basic principles with sculpties. Bottom line: my efforts of the past week went astray as I allowed confusion to set in, casting about for the proper maximum texture dimensions working down from 1024. (and I’ve got the awkward attempts at 1008, 994, and 978 pixels to prove it).

In fact, the answer is very simple in reference to basic sculptie principles, as the maximum dimensions of the sculptie bumpmap are 32×32, and due to the need to wrap it around to an apex underneath, this can only represent a 30×30 terrain patch. Thus, the maximum imageable area is simply (30/32)*1024, or 960 pixels square, collared out to 1024 square to make each orthophoto tile. This means that an OpenSim 1.024:1 model can accomodate 130mm orthophoto imagery, and I now have 160 tiles ready to go with the bumpmaps.

So far I’ve configured twelve regions with their megaprims, and only one seems to have issues with the height of the sculptie to stay 30cm afloat the terrain surface. Nine of these reigons use the flattest setting, one uses the intermediate, and two use the steepest. Here’s some shots for update’s sake. The full set of orthophoto textures have been uploaded (450 MB of Targa files) and seem to show up reasonably well in inventory. I am using a local MySQL instance on the OpenSim machine for prim storage.

OpenSim Berkurodam 40-region sim More OpenSim 40-region Berkeley model OpenSim 40-region Berkeley model

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