Introduction: Gaia Horizon / 3d Machining With LIDAR Point Clouds
Gaia Horizon is a sculptural series that explores landscapes as an assembly of images, edits, and distortions, how various technologies have been used to image terrain on other planetary bodies, and how these tools and techniques have shaped the way we view our terrestrial horizon through dimensional satellite scans and crowd-sourced imagery.
While this work uses CNC machining, my interests here were heavily influenced by photography, specifically images produced over decades by NASA, stitched panoramas of the Moon’s surface sent back from Apollo missions, to the color shifted stereo photography of the Martian surface, to even staged photographs in extreme environments on our home planet to understand what terrain might be like elsewhere.
The purpose of this Instructable is to give an overview of a technique I used to produce this work, using LIDAR point clouds to 3D carve terrains into various materials using a CNC machine.
Image Credits:
1-2: Gaia Horizon, Gaiam yoga blocks CNC machined using a LIDAR scan of Death Valley, CA, courtesy Steve Gurysh, 2015. http://www.stevegurysh.com/plateau.html
3: Mosaic of surface images taken by Surveyor 1, pasted onto the inside of a hollow sphere to preserve the view geometry of the camera, 1966, courtesy of NASA and JPL. http://www.airspacemag.com/daily-planet/surveyor-1-americas-first-lunar-landing-180959289/
4: 'Payson' Panorama in False Color from Opportunity program, 2006, courtesy of NASA/JPL-Caltech/USGS/Cornell. http://mars.nasa.gov/mer/gallery/press/opportunity/20060307a.html
Step 1: Sourcing LIDAR Data Sets
There are many ways to access free digital elevation models, it really depends on the quality of the scan and the specific details of the geography itself that will dictate where you should start to source material. I’ve seen other tutorials that use Google Map data, however this usually produces very low resolution 3D terrains. While these might be perfectly fine as a digital asset in a screen-based application, these meshes are typically too low quality to be worth carving into material if you want a high level of detail.
For higher quality results, I’ve had a lot of success with is what is called a LIDAR point cloud. LIDAR is a remote sensing method that uses light in the form of a pulsed laser to measure ranges (variable distances) to the Earth. These are produced either on the ground with teams of people or via aircraft equipped with high quality laser scanners. While the collection of these scans is a highly specified skill using lots of expensive equipment, luckily there are a few repositories online that share LIDAR data sets for free.
One of my favorites is a site called OpenTopography (opentopo.sdsc.edu)
“OpenTopography harnesses cyberinfrastructure developed at the San Diego Supercomputer Center to allow users to access and process LIDAR point cloud data on the fly for an area of interest. The goal of the system is to provide a web-based toolset that can democratize access to massive and potentially computationally challenging community LIDAR topography datasets.”
For the purposes of this Instructable, you'll want to navigate to DATA > LIDAR POINT CLOUD and then scroll to select a region of interest.
On the next page, you'll be instructed to select a region within the data set for download. I would suggest that you start with a small selection before you end up with a file size that's too unwieldy to manage.
Make sure that you have selected *Point cloud data in LAS format
Then fill in the information at the bottom of the page to receive download instructions via email.
Step 2: Importing LIDAR Point Clouds
Once we have a data set saved as a .LAS, we’re going to want to convert this file into something we can use in our CAD/CAM software, something we can use natively to create a tool path for the CNC.
Luckily someone has already created a really great tutorial that uses a free open-source program called 3DEM (Windows application only)
Downloading DEMs
https://www.youtube.com/watch?v=8r4B231CddE
Converting to VRML in 3DEM
https://www.youtube.com/watch?v=uObN5AwIw8s
Importing into Rhino
https://www.youtube.com/watch?v=NUa_fJXFjLc
Once your file is prepared, it’s possible that you will want to reduce the resolution of the mesh to make it more workable as a smaller file in your CAD software. MeshLab is a great open source tool to use for this.
Step 3: Tool Pathing Terrain
Stock Material
There are a few things I’d like to cover when it comes to machining detailed 3D surfaces. The first consideration centers around our stock material. It's best to start out with low density materials like foam, just to get a sense of the process. You can run tests quickly and you won't need to worry much about breaking bits or wasting time with roughing passes. Of course, it's always ideal to start small, run some test samples before taking on larger areas. 3D machining can be incredibly time consuming and you'll want to be sure you have everything dialed in before you start a multi-hour long cut.
Once you feel comfortable to move on to higher density materials, hardwoods, plastics, aluminum, all machine beautifully with this technique.
Tooling Selection
Most 3D carving operations will require a roughing pass, followed by a finishing pass. Roughing passes are more critical when using dense materials. Not only will this technique extend the life of your finishing tooling, but it can often improve the surface finish of your part.
Generally speaking, in a roughing pass, you want to select a flat end mill that will provide the largest cutting area. Here, we are just trying to remove as much material as possible to prepare for the finishing pass.
While ball end mills are ideal for 3D machining, "tapered tooling" is a specific flavor of router bit that is really well suited for producing detailed textures at higher speeds. Of course the smaller the diameter of the bit, the higher detail you’ll be able to achieve. However with a taper tool you will be able to run at a much higher RPM and feed rate since the shaft is wider than the cutting edge on the tip of the tool. This can save hours of machine time.
I recommend experimenting with different tooling diameters and geometries before settling on a specific tool. Tool selection will greatly effect the aesthetic and quality of the final product. Do you want to see tooling marks? What size are the smallest details that you want to reveal?
Tool-Pathing
Once you have something to work with in Rhino or Fusion 360, there are many ways you can go about creating tool paths to begin 3D carving these surfaces. In most CAM software there will be several different 3D machining operations to choose from: radial, spiral, parallel finishing, adaptive clearing, etc. Selecting a preference for one or the other can create more efficient tool paths, saving machine time or simply produce a desired aesthetic result.
Of course the other major variable that effects levels of detail and machine time is the amount of step over in relation to the tool diameter. In RhinoCAM this is found in Cut Parameters. This will take a bit of experimentation to achieve desired results, but just for example, to produce Gaia Horizon, I used an Onsrud 77-114 1/4” Upcut Taper Tool, running 18,000 RPM @ 600 IPM and using a 5% step over. For this particular work, I was carving into yoga blocks, which is EVA foam, it carves really nicely. I've also used this technique in carving hardwoods like maple. For this I've used smaller diameter taper tools, but would recommend doing a roughing pass with at least a 1/2" ball end mill.