Fourteen years ago I was on a quest. I knew that 3D altitude data of Mars was available online because I had seen it used in illustrations for National Geographic and other magazines. I wanted to figure out how to find the data and use it in my own 3D modeling software. This wound up being more complicated than I had anticipated and took several months of gradual tinkering, lots of e-mails, and some help from people who were doing it. Finally, I succeeded. I had to download the data as uncompressed .img files from the Mars MOLA data page at the NASA Planetary Data System Geosciences Node housed at the Washington University in St. Louis (WUSTL). Try saying that five times quickly . . . I then had to use some freeware software called 3DEM that could load the Mars .img files in directly, then export them as TIFFs or PNGs that I could crop in Adobe Photoshop, then load into my software of choice, Daz3D Bryce, as a grayscale heightmap.
One person that gave me valuable advice was Kees Veenenbos, whose Mars renderings appeared on the cover of National Geographic. He e-mailed me back and explained where to find the data and how to use Terragens to model it. Years later, when I met Artemis Westenberg as part of the Mars Education Challenge, I told her how I got started doing 3D Mars images and she told me she was good friends with Kees, and that she had some laminated posters of his images. Would I like them? Well – of course! They are hanging on the walls of my classrooms. Here is a link to a Huffington Post article about Kees’ work: http://www.huffingtonpost.com/2013/04/03/mars-renderings-kees-veenenbos-images_n_3000366.html
In the years since, system software changes have made 3DEM obsolete. I tried loading the data into Adobe Photoshop as a raw image, but ran into a problem. The Mars data uses an aeroid, or “sea level” measurement as a zero point, and the altitude data is measured up and down from that level. However, Photoshop can’t read negative data. It created two gradients, one for the positive elevation and one for the negative. I figured out a work around in Photoshop, but it left a kind of bathtub ring where the data had to be blurred at the aeroid. I was able to use this technique for our lunar animations, but it wasn’t ideal.
In the meantime, I had started using a program from the National Institutes of Health called Image J. It allowed me to turn numerical data into a grayscale image. After years of using it for other purposes, it occurred to me one morning last year that it might be able to read the Mars .img data. I tried loading it in using the Import-Raw menu and found it had a choice for 16-bit signed data import. That sounded promising. I chose one of the 16 Mars quadrangles from the MOLA data site, typed in the size of the images (11520 by 5632 pixels at 16 bits per pixel) and chose OK. Viola! There was the data, in all its detail!
Since then I have used Image J for Mars and lunar data. I recently recorded a video demonstrating the steps for using this data in Daz3D Bryce. Here is the link to the video in YouTube: https://youtu.be/kzdO9PANu_8
Once you get the image cropped and saved in a format such as a 16-bit PNG or PGM, most 3D modeling programs can load it in as a grayscale height map and create a terrain out of it. I find that and entire Mars quadrangle is rather large for most 3D software to handle, so once I save it as a PNG or PGM from Image J, I use Photoshop or other image manipulation software to crop smaller pieces from the data, which I build into terrains.
I have experimented with printing out these models with a 3D printer. I use Daz3D Carrara to load a cropped height map onto a terrain model, then build a frame around it, rotate the terrain and frame 45 degrees, then build a support underneath it. By rotating the model, I can use the maximum resolution of the printer and avoid printer-added supports so that no clean up is necessary. It’s taken some experimentation to get the size and structure of the frame right, but we have had a few successful prints.