HiRise data and WRL Conversion:

It has been a while since I last posted an article due to being busy with other projects. During some research activites, I came across a number of subjects that may be of interest, two of which I would like to share.

The first one is the HiRISE Digital Terrain data models on the University of Arizona website. The website contains datasets that are digital extractions of surface terrain scans of the planet Mars. The DTM datasets are publicly available for research and modeling of geological processes.

Naturally curious I decided to investigate the possibilities of modeling and rendering of these datasets from which I produced a few preliminary 3d terrain models using Blender and rendered in Keyshot…Gorgonum Chaos:

The technique I used is described in this video on Youtube, clearly explaining the process. To me, this is incredible stuff and thanks to the University of Arizona for all their dedicated work in developing these datasets. So have a look and check it out for yourselves.

The next subject is WRL. WRL is a file extension for a Virtual Reality Modeling Language (VRML) file format often used by browser plug-ins to display virtual reality environments. VRML files are known as “worlds,” which is what WRL stands for.

One of my many interests is Tensegrity, a structural form of tension and compression members first developed by a chap called Kenneth Snelson. The internet is full of examples of this structure concept inspiring many variations from fairly simple to very complex designs. I have developed a few of my own.

Many of the practitioners in this field make datasets available for personal use and one particular format they use is the VRML (WRL) so you can view the design in 3d.

For the simple structures similar to this image the design and construction are not that difficult, however when it comes to developing your own version of the more complex examples it can be a real headache. Although some datasets include actual point cloud data the process of matching pairs of points to reconstruct the design can be a nightmare.

The obvious solution would be to convert the WRL model into something usable that could be used as a guide for developing a 3d cad model. I tend to favor Meshlab for doing this as it is one of the few programs that will accurately convert the imported data.

The WRL model is converted into a series of mesh objects that we can export as an OBJ or STL file and then import into Inventor.

Once in Inventor, it is simply a case of selecting each of the compression struts and “Fit Mesh Face”. Select the “Auto Fit” option for each member and it will create a surface from each mesh representing the struts.

The tension wires are then created as a 3d sketch using the background mesh model as a guide. At this stage, the model is a workable composite but may require micro adjustment for the tension wires to ensure the finished item is properly constrained. I would reverse engineer this model and reconstruct as an assembly and apply the microdimensional adjustment to the groups of tension wires to ensure the absolute accuracy of the final design.

It is beyond the scope of this article to go into the detail of every step, but if you require information on any of the topics please feel free to drop me a line.

I hope you find this article interesting and have fun.