3D model of Mars for 3D printers
DEM (Digital Elevation Models) are files which contain maps of elevation of a territory. DEM files are sometimes found on google image search presented as greyscale images, with white at the high elevations of the map, and black at the low elevations.
If you search google for DEM elevation images you'll get image results a bit like this:
You should choose the ones which do not look like renderings and do not have colors. For example the last three on the top row are probably renderings of heightfields, they have shadowed hills, which means the image itself is not a true heightfield.
The images which look like medical images, with no 3D shadows but just strange 2D shapes are likely to be true heightfields.
In the example search above, all those with a gree rectangle around them are true heightfields which you can use with PhotoToMesh to produce a reproduction of the terrain.
This makes them perfect for creating heightfelds for 3D printer STL files.
But even more wonderfully there are DEM maps of whole planets. One which is easy to find is the Mars DEM grayscale image. Search for DEM maps of Mars :
Only the ones inside the green rectangles are suitable. The others either do not cover the whole of the planet, or they are in color, or they are renderings of DEM maps.
Now I could put this on a sphere in PhotoToMesh to print, but some printer's software fill in the sphere with plastic, even if the model is hollow. So I've tricked my XYZPrinting DaVinci software into printing a hollow sphere but really printing a bowl which almost occupies the whole of the sphere. If your printer's software respects the hollowness of closed STL models then you can use a sphere. My doesn't, I've had to use a bowl, as shown below:
Step 1: Make sure you have selected Show Front/Outer image as shown in the above screenshot at middle left.
Step 2: Open the image file and click on Next on all the wizard import options. What you'll see is probably not what you see above, because the other settings have not be done yet.
Step 3: Choose Bowl as the Solid Shape, and you may get an image like this:
It does not look like a planet yet, it looks like a, well, bowl.
Step 4: Click on the "Other Settings..." button and you'll get a dialog which allows you to change things about the bowl. Set the dialog to look like the one below...
...and click on OK:
In PhotoToMesh a bowl object is based on a sphere. When we set the "Bowl Height In %" as shown in the dialog above, we are telling PhotoToMesh to use 98% of the sphere's shape.
Step 5: Make sure the image placement is correct. WIth PhotoToMesh you can place the image in various positions of the model you are creating. To put a full globe Digital Elevation Model image on a sphere you need to make sure that the image is centered and covers 100% of height and width.
To do this click on the Image Placement... button an set the dialog to look like this:
Now, more on the other settings in the main dialog. (My setup works in millimeters, all you have to do is scale it to your own units if you work in Imperial measurements.)
X Samples (around the equator) is set to 700, as is Y samples (along longitude). This means that there will be roughly 700x700 triangles in the final object, which gives a decent resolution. You can do more or less according to your printer, how long you want to take printing the object, and so on.
The Diameter of equator (x), Diameter of equator (y) and the Height of the meridian are all set to the same value of 100. This, for my printer, means a sphere of 100mm size. PhotoToMesh allows you to have independent x y and z diameters (for oblate spheroids). But if you want a sphere (like I do in this case) keep it to a single value.
The "Height" of mesh is how far the image will move the surface off the perfect sphere. I've set it to 4mm, which is more than 10 times it's correct value of about 0.32mm (explained here). My printer is not so brilliant and I wanted a dramatic map of Mars where you could actually see the mountains and ravines.
The Wall Thickness is set to 1mm, which in essence sets the thickness of the thinnest part of the sphere/bowl. So the sphere will be between 1mm and 5mm (1mm + 4mm) thick.
I've set the Smoothing to 0. Again my printer's resolution is not brilliant and I did not want to smooth out any interesting features.
Make sure that Invert Mesh is not selected, else your mountains will become valleys and vice versa.
Now all you need to so is to save the STL file of your Mars globe and print it!
By the way, there are many DEM images out there, most are of rectangular areas on the Earth...
...and some of planets, asteroids, moons...
I've set my model to be a sphere of diameter 100. Now Mars has an average diameter of 6794 km. And the tallest mountain, (Olympus Mons), is 22.2km high. So if hmm is the height of mesh in mm...
100/6794 = hmm/22.2
hmm = 100*22.2/6794 = 0.33mm
But as I explained, I wanted more drama in my print, so set the height to 4mm! If you want a more realistic and larger 3D print and have a high quality printer you could set the diameters all to be 200 and the mesh height to be 0.66. That way you've only exaggerated 200%!
Olympus Mons, in our original image, is the white (hence high elevation) blob shown below:
You can try the demo PhotoToMesh free and gratis, download the program by clicking on the button below: