I wish I knew anatomy as well as Mauricio Antón, but I don’t. Apparently, neither does National Geographic – a source of information that I would like to think of as knowing things I don’t. Alas… in an illustration specifically about the skeletal anatomy of the cheetah, they manage no less than 4 fairly major errors. The erosion of media authority continues. Mauricio Antón is the goto guy… clikc the cheetah.
At last year’s DigitalFossil – organized by Heinrich Mallison and populated by all sorts of innovative specialists – motivated me to share some modeling / shading techniques from the workings of vfx. In particularly, I’m motivated by Julia Molnar’s talk about modeling abstracted bone volumes – not because one technique is better or worse, but because they are different. Julia presented a cool remodeling method for quickly reducing resolution of a scanned bone while roughly maintaining volume. She relied on lofting profile curves and it worked wonderfully. In Vfx, volume maintenance isn’t the goal of remodeling… you get it as a side-effect of creating models that render efficiently at various levels of detail. The most-common method relies on a combination of subdivision surfaces and image-based displacement. Subdivision surfaces (sub-d’s) means a mesh (points in 3D space forming faces) but which are subdivided according to a smoothing algorithm that makes them behave at least a bit like nurb surfaces, which are not defined by points but by mathematical equations. Sub-d’s are really powerful because they can be deformed in the low-res version and then further subdivided and displaced according to pixel or procedural textures.
I’m going to walk through this process, taking a crocodile skull from the University of Texas from scanned mesh to a sub-d mesh with pixel-based displacement. I’m writing this for scientists, but I hope it’s generally of use. Also, keep in mind that there are many possible methods to get from A to B, and also that the technologies are constantly evolving – so methods have to be assessed according to the intended use and available time.
First, get your crocodile skull. It’s downloadable as a stl file – a bunch of points in 3D space connected by faces to represent a surface. you can get it into your 3D software (like Blender) by importing or loading. You may have to convert it to a compatible format – I had to convert it to a dae (collada exchange format) to get it into modo. Blender is great for these things… it’s likely the best format converter out there, with the exception of license required max files and full scene formats. I’ll be working with modo from here on in, but all the steps can be replicated using whatever software you choose.
That’s as far as I’ll get today, which is already enough to 3D print! Well, okay, cleanup required, as this cool tutorial for maker bot shows.