Converting Lunar Reconnaissance Orbiter elevation data for usage in TG2

[Laskaris]

Hello everyone! I have just discovered TG2 and am trying to use it (the free version) to do renderings of the lunar surface, using real elevation data from NASA. Depending on the results, I might buy the full version of TG2.

This is the dataset I am trying to convert to some format TG2 can use:
http://wms.lroc.asu.edu/lroc/global_product/128_ppd_DEM

It is in PDS (Planetary Data System) image format, with a *.img file extension. I have read this thread and others with suggestions on how to make the files useable in TG2, and tried to put them into action.

First off, I converted the .img file to .png using img2png, a command line program. I can't load the .png in TG2, though. I get the error message: "Please convert image to SGI for non-standard bit depths." Presumably, this is because the .png is 16 bit, which TG2 can not handle?

Next, I converted the .png to a 16 bit .tif with Photoshop, but got the same error message. I thought TG2 can handle 16 bit .tif files? Is this correct? If so, there must be something about this particular file / type of .tif that prevents TG2 from being able to read it.

So, I reduced the 16 bit file and made an 8 bit .tif with Photoshop. That one loads up fine in TG2.

It's a pity, though, that I can't figure out how to use the 16 bit data in TG2. Does anyone have a solution for this? I know that other people have experimented with these lunar height maps, so maybe one of you can help.

Any other tricks and tips on how to make a good lunar scene would be appreciated as well.

[Tangled-Universe]

Welcome to the forums

It's not really clear to me either about how/which file formats support 16-bit in TG2.
If I have a 16-bit file, say TIFF, I always save it as .SGI in Photoshop and load that succesfully in TG2.

You can find the SGI plugin for Photoshop here:
http://www.telegraphics.com.au/sw/product/SGIFormat

The CS4/5 version works also in CS6 on my PC.

Cheers,
Martin

[Oshyan]

TG2 supports 32 bit (floating point) single-channel ("grayscale") TIFF in PC byte order, with no compression or layers. I don't think 16 bit TIFF is supported, which may be surprising, but I believe GeoTIFFs are generally 32 bit. Broader support for high bit depth formats will be available in the future. For now you can go into Photoshop, convert to 32bit/channel and grayscale, then save and make sure no compression is being applied.

- Oshyan

[Laskaris]

Thank you both for your replies.

I downloaded the SGI plugin for Photoshop and converted the 16 bit .png to a 16 bit .sgi with it. However, TG2 crashes when I try to load that .sgi file as a heightfield.

I notice that TG2 also crashes when I try to use the larger heightfield files (the 256pixels/degree and 100meters/pixel versions from the LRO site) as .tif files. I can only load the smallest version of the elevation maps, the 128 pixels/degree, as a .tif heightfield. I suppose that this could be a RAM issue?

Edit: When I cut out only a small part of the 100meters/pixel .tif, and try to load that one as a heightfield in TG2, it works. It really seems to be a size / RAM issue.

[Oshyan]

How much RAM do you have? Are you running on a 64 bit OS with the 64 bit version of Terragen? There really shouldn't be any memory issues on a 64 bit system unless you have a really limited amount of system memory (e.g. 4GB or less).

I will say that TG doesn't crash terribly often, and in my tests with various file formats, incorrect/incompatible ones did not cause crashes, however running out of memory is definitely one of those situations where crashes can happen.

- Oshyan

[Laskaris]

How much RAM do you have? Are you running on a 64 bit OS with the 64 bit version of Terragen? There really shouldn't be any memory issues on a 64 bit system unless you have a really limited amount of system memory (e.g. 4GB or less).

I will say that TG doesn't crash terribly often, and in my tests with various file formats, incorrect/incompatible ones did not cause crashes, however running out of memory is definitely one of those situations where crashes can happen.

- Oshyan

My PC has a 32 bit system and 4 GB or RAM. I take it that is not sufficient, then, to work with the large files we are talking about here in TG2?

[Oshyan]

Most likely you are correct, that's not a lot of RAM to be working with unfortunately. You could use lower resolution files though...

- Oshyan