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Need help getting hightmap in correctly.

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Need help getting hightmap in correctly.

Postby Servo » Thu Nov 20, 2008 7:47 pm

I am trying to get in a gray scale hightmap of the world in and parts of the terrain import ok but I’m not sure what setting to correct to get it in ok since when importing it asks for max high and lows and so on..
This is the height map image reduced in size to be able to post it here.
Image

And this is the PNG file
http://www.interceptorshield.com/DEM/EarthDEM2160.png

Could someone maybe take a look and let me know what I need to do to get it in proper into L3DT. I could really use a little advice on this since I'm really new to useing L3DT.
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Postby Aaron » Thu Nov 20, 2008 9:48 pm

Hi Servo,

You should use these settings:
  • Horizontal scale: 9276 metres (determined by circumference of earth and number of pixels in image)
  • Min. alt: -10900 metres (depth of Challenger deep in Marianas Trench)
  • Max. alt: 8848 metres (height of Mt. Everest)

You'll also have to manually adjust the sea-level after you import the map. This is because the spatial resolution of the map is a little too coarse to accurately set the altitude range based on the extents above. To do this, go to 'Operations->Heightfield->Change vert. scale' in the menu, and setting the '% above sea-level' value to 31. These settings put the sea-level to within about 10 to 20 metres of where it should be (see below). If you're after super-accuracy, you can tweak it a little more by increasing or decreasing the 'average altitude' setting in the vertical scale dialog.

Image

I hope this helps.

Best regards,
Aaron.

PS: If the original source of this image was a DEM, it might be helpful to run it through VTBuilder to convert it to a BT file, which L3DT can read natively. If you do this, you won't have to mess around with horizontal/vertical scaling, because DEM and BT preserve this information correctly, whereas PNG does not.
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Postby Servo » Thu Nov 20, 2008 11:02 pm

aaron thanks for the quick reply I tried the setting you suggested but it did not turn out like how yours did this is what my one looks like

Image

As you can see more above not like how your one looks, when I go into 3D view the terrain is rather boxy.
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Postby Servo » Thu Nov 20, 2008 11:59 pm

I found out the problem I had show contoure lines on. I turned it off and it now looks like yours.

I have a texture file that is of the globe that goes with that dem file how do I apply it so the terrain uses the terrain file?
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Postby Servo » Fri Nov 21, 2008 2:12 am

I want to apply a world texture sorta like ths one but I have one that is so scale with the hightmap that can be overlayed. but I dont know how to set a texture for the terrain.

Image
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Postby Servo » Mon Nov 24, 2008 10:15 pm

inside VTbuilder how do I save to BT file format? I cant find that option
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Postby Aaron » Tue Nov 25, 2008 9:49 am

Hi Servo,

Use the 'Layer->Save layer as...' menu option. Note that this option won't be enabled unless you've imported your DEM using the 'Layer->Import data' menu option and then selected 'Elevation' in the Please indicate your layer type dialog box.

Please let me know if there are any problems.

Best regards,
Aaron.
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Postby Servo » Tue Nov 25, 2008 4:42 pm

ok I got it to save the hightmap DEM file to BT format in Vbuilder, but when I import the BT file into L3DT the terrain is just about praticly flat even mountin ranges that should have some noticeable hight.
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Postby Servo » Tue Nov 25, 2008 7:35 pm

This is what the terrain looks like its missing all the mountains and details that the DEM file had.

Image

This is the DEM file I am using
http://edc.usgs.gov/products/elevation/ ... 40n40.html
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Postby Aaron » Wed Nov 26, 2008 11:15 am

Hi Servo,

To see vertical relief I think you'll need to get closer to the terrain surface. That screenshot was taken from an altitude of 30,000ft. You can also increase the detail of the heightfield mesh in the viewer by pressing the '0' key*.

Can you tell me what the horizontal resolution of the DEM is? If you're not sure, go to the 'Operations->Heightfield->Change horiz. scale' menu item.

Best regards,
Aaron.

* Note this will reduce the frame rate. You can press '9' to reduce the detail and increase fps again.
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Postby Servo » Thu Nov 27, 2008 12:21 am

the scale on the dem when I load it says its set at 2911.


I have incressed the detail level and this is what it looks like at ground level.

Image
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Postby Servo » Thu Nov 27, 2008 6:42 pm

Ok I got it so the mountains are now showing as they should by reducing the horizon scaling.

Now here is the main question. I have a bunch of high maps that are not of even scaling. Is it possible to scale the hightmaps in L3DT so they can be exported to atlas terrain??

Basicly I want to combine 32 hightmaps of the world together to make one detailed hightmap that I can export into atlas but not loose scaling on details.
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Postby Aaron » Fri Nov 28, 2008 9:52 am

Hi Servo,

Servo wrote:the scale on the dem when I load it says its set at 2911.


Hmm...that's odd. The resolution of that GTOPO30 DEM should be 30 arcseconds, which works out as about 900 metres, or about 2900 feet (not 2900 metres!). This makes me think that either VTBuilder is incorrectly reporting the scale units, or more likely, that L3DT is not properly reading the BT horizontal scale. I'll download the DEM an have a poke around.

In any case, I should think the DEM resolution is rather poor for most types of games, since the smallest feature that can be represented in that DEM is a shade under a kilometre wide (or a bit over half a mile, if you prefer old-school units). For FPS/FP-RPG style games I normally recommend a horizontal scale of between 0.5m and 2m for best results, and for RTS and flight-sims no more than about 20m. Nine hundred metres is rather coarse indeed.

If you're after higher-resolution DEM data, you can freely download the 1 arcsecond (~30m) resolution Shuttle Radar Tomography Mission data from NASA's ftp server here. VTBuilder should read these files OK (or so says the FAQ).

Servo wrote:Now here is the main question. I have a bunch of high maps that are not of even scaling. Is it possible to scale the hightmaps in L3DT so they can be exported to atlas terrain??


It's possible, but somewhat difficult. If you have tiles of different horizontal scalings, you will first need to rescale and resize them to change the pixel density without changing the physical extents. After all your tiles have the same pixel density, you can import them into one big file by repeated use of the atMergeMap plugin, which is included by default with the more recent builds of L3DT. Please note that it may be advantageous to update to the most recent developmental build (see downloads page), as it supports 'undo' for the map merging operation, which may be useful as mistakes are easy to make with this interface.

Servo wrote:Basicly I want to combine 32 hightmaps of the world together to make one detailed hightmap that I can export into atlas but not loose scaling on details.


That sounds rather challenging. As I understand it, Atlas has an effective upper limit of 4096 x 4096 heightmap pixels per file at present. Furthermore, multiple Atlas files cannot currently be stitched together in TGEA without showing seams or gaps.

Cheerio,
Aaron.
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Postby Aaron » Fri Nov 28, 2008 10:36 am

Hello again,

aaron wrote:The resolution of that GTOPO30 DEM should be 30 arcseconds [...] This makes me think that either VTBuilder is incorrectly reporting the scale units, or more likely, that L3DT is not properly reading the BT horizontal scale. I'll download the DEM an have a poke around.


As expected, the bug was mine. L3DT's BT plugin was incorrectly calculating the horizontal scale when loading BTs encoded with latitude/longitude extents in degrees. It was off by a factor of pi. The fixed plugin will be included in the next developmental build. I apologise for the inconvenience caused.

Best regards,
Aaron.
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