[osg-users] --tile-terrain-size in VPB

Martins Innus minnus at ccr.buffalo.edu
Tue Mar 24 12:14:06 PDT 2009


Robert,

	It seems that this issue is caused by the use of DrawElementsUShort and 
"unsigned short" indexes in "osg::Node* 
DestinationTile::createPolygonal()".  Such that each level can only have 
a maximum of 65536 vertexes.  And I do see that a terrain-tile size of 
256x256 works, yet 512x12 doesn't, which makes sense.

	Is this something you'd accept a change for to be included in VPB?  Not 
sure what the performance implications would be, or how extensive the 
changes would need to be.

Martins

Martins Innus wrote:
> Robert,
>     What fun would it be if people didn't abuse your code :)  I agree 
> that in general VPB does a great job with default settings, I've used it 
> several times to generate 100 GB databases over large areas.
> 
>     In this case though I'm trying to generate terrain at the resolution 
> of the source data for a very small area in as few tiles as possible. I 
> realize this is not the intended purpose, but I was trying to see if 
> anyone had done this successfully.
> 
>     It doesn't seem to be a display issue, becase I can generate the 
> model with default options and load all the highest resolution tiles 
> directly into osgviewer and it runs fine, about 4 million vertices.
> 
>     Going down to 512x512 causes the same problem.
> 
>     I'll keep digging if no one has run into this before.
> 
> Martins
> 
> Robert Osfield wrote:
>> Hi Martins,
>>
>> Jikes, some days I regret making osgdem quite so flexible...
>>
>> A 1024x1204 grid weights in at million vertices, and near two million 
>> triangles.  Normally graphics cards should be able to handle this, 
>> but... it would seem that your's doesn't, perhaps it just doesn't have 
>> the memory to handle such a big geometry.  The other chance might be 
>> that numerical precision is becoming an issue, although I'd be 
>> surprised by this one.
>>
>> I really would very strongly recommend that you stick to defaults 
>> unless you really know what you are doing, the defaults are chosen for 
>> a good performance and scalability.
>>
>> Robert.
>>
>> 2009/3/23 Martins Innus <minnus at ccr.buffalo.edu 
>> <mailto:minnus at ccr.buffalo.edu>>
>>
>>     Hello,
>>            I'm using the --tile-image-size and --tile-terrain-size
>>     options to tweak the generation of the dataset.  The image option
>>     works great, but when I try to use the terrain option I get the
>>     results attached.
>>
>>            If I zoom in, it seems like a lot of overlapping geometry
>>     like the y-coordinate is not being updated properly, but I dug
>>     through the code and could see any obvious causes.
>>
>>     I'm using the following command-line:
>>
>>     osgdem --tile-image-size 4096 --tile-terrain-size 1024 -t
>>     ../input_ims/ -d ../input_terrain/ -e 1065536 1043840 8192 8192 -o
>>     output/vpb_out.ive
>>
>>     I even added --no-terrain-simplification to see if that was the
>>     problem, but no help there.
>>
>>            I'm not using the --TERRAIN option, since I need to
>>     post-process the geometry using an existing tool.
>>
>>     Thanks
>>
>>     Martins
>>
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