New Bathymetry

[simaddons]

Just resampled an ETOPO1 Bathymetric world cover.

Source is NOAA ETOPO1, convert to GeoTIFF, resample to .bgl



Elevation is correct, LOD 4 resolution.



Need some help how the Prepar3D Bathymetric works.

1. Submarine settings

2. How to go underwater (visual)

3. LOD minimum (to overwrite topo water '0')

[beatle]

Hey Ralph,



I believe the online SDK docs are going to be updated sometime in the next week with info on the Bathymetry data stuff.



Tim

[simaddons]

Have it - works!



Scenery is my Toronto CYTZ, Billy Bishop City Airport.

I have add a local DEM mesh below lake Ontario, LOD is 16

Mesh resolution is 100/1m/0.6m for good lake borders.



It works also with LOD 12 or 13. No lower resolution tested.



So as I understand, you need a Bathymetric mesh to go underwater.

[Beau Hollis]

Awesome,



There is a bathymetry data flag which can be set when creating a bgl (keep an eye out for this in a future SDK release), but we don't currently require it.



You have stumbled upon one of the positive side-effects of our latest bathymetry implementation. Before, we had to restrict bathymetry to oceans and coastal regions so that we could assume water surfaces were at sea level. Now, we use the pre-flattened dem elevation as bathymetry, while the surface is determined by flattening to the vector data. We hoped this change would support lakes and rivers above or below sea level, but it was an untested capability prior to your investigation. Thanks for testing it out. I'm really glad it worked.



Beau

[Beau Hollis]

Also, this should be in the SDK or learning center, but you can go underwater in slew mode.

[simaddons]

Thanks - was surprised too. Lake Ontario is 71m above sealevel.

Another sample works too, is in Halifax on sealevel.



Is there a minimum LOD? Or must it be same/higher than the land LOD?

I use at both places photo scenery.



Slew - yes, but if you have scenery data like extrusions you see it all.

Bathymetry is very fun and "mask" it perfect, but gives us developpers

a little bit more work to finish all scenery details underwater.

[Beau Hollis]

Right now, there is one dem used in the final scene which stores two elevation values per point. Thus, the runtime LOD is going to be the same for land, water, and bathymetry. Prepar3D interpolates/extrapolates values when the mesh LOD differs from the source data, so you should be able to create bathy source files at a different resolution than your land data. I will check the data guys to verify.

[simaddons]

Thanks for the feedback



I use different LOD's, as sample

- photo mesh is max. LOD15, include water mask

- bathymetry is max. LOD13, include mask for nothing = no problems with land DEM LOD 12



My world mesh is not working, LOD 4

[Orsor]

hey Simaddons,



I'm one of the data guys!



To get the world mesh to work, it has to be "up-sampled" to a resolution equal or higher than the default resolution of the DEM for each level 4 QMID scenery area.



In most cases this is 0.00083333 decimal degrees for areas outside the United States. US uses a 30m mesh - 0.000277777 decimal degrees.

[simaddons]

Thanks Orsor



Just "up-sample" an Atlantic area - huge files.



Also on work is Lake Ontario - perhaps we can upload it for other users.

Source is NOAA -> Great Lakes, grid cell 3 seconds.

[Orsor]

Yes, I realize that upsampling 2/3rds of the earths surface would take an enormous amount of space. imagine when we have real 30m elevation models for the entire worlds bathymetry!



If you have access to SRTM or NED Elevation models it would be possible to replace the default DEM .bgls in the scenery folders too.



Our DEM####.bgls in the scenery folders are resampled to 0 where we had "no data". So if you have the source you could replace it and this time resample no-data to actually be no-data. The drawback to this is that you would lose the airport edge smoothing.

[simaddons]

Success - here some data infos.



For the above area (Atlantic Canada) I must up-sample to LOD 11 = 0.000683974 (76m)

File size is 533 MByte. Works perfect, FPS > 100.

Will now adjust my offshore platform and upload some pictures tomorrow.



I use this for the resample.exe



[Source]

Type = GeoTIFF

Layer = Elevation

SourceDir = "."

SourceFile = "Atlantic.tif"



[Destination]

DestDir = "."

DestBaseFileName = "atlantic_bathymetry"

DestFileType = BGL

LOD = Auto,11

UseSourceDimensions = 1



Lake Ontario also runs with LOD 11 - file is 38MB - file is up.

Download here: http://www.prepar3d.com/downloads/



Yes - I have access to SRTM, DEM and more.



BTW: Is there a trick to adjust underwater texture?

Or simple use "Water Classification" = LC/WC file.

[Beau Hollis]

Right now, each runtime db tile only has one texture. We didn't have enough time to sort out the technical issues with introducing and managing a second texture - it sounds much easier than it is . Hopefully this will be addressed in a future release.

[Airtrooper]

I can't find the reference in the SDK for the usage of resample.exe with bathymetric data. In other words I don't know what the data flag is for bathymetry. Can anyone enlighten me? If it is in the SDK documentation can someone point me to the correct place please?

Many thanks

Andy