Producing data-driven holograms with Python/Blender/FBX
Reviewing the options for game development with Unity and Visual Studio was intimidating to say the least. It looked like I would need to learn C# while adjusting to the Unity → export to Visual Studio → compile to Hololens toolchain. Worse, while I could follow along the Unity introduction to make a ball roll around a plane, I wasn’t able to export this basic demo to Hololens after hours of re-installing various versions of software.
I started wondering if Blender might let me produce animations for hololens, knowing that it allows for python scripting, which might allow my pythonic-data-scientist-coworkers to jump into producing holograms much faster than writing our own video game without any game engine experience.
Now, there are many guides on how to design things in Blender, import the meshes and actions into Unity, which can then export the project to Visual Studio for compilation. I hate the idea of dealing with that toolchain, dealing with incompatibility and export quirks each step of the way. I want to write a python script that produces an animation for Hololens.
With a little googling, I discovered that Hololens can indeed display animations in the FBX file format which Blender is happy to export, so I started playing around with the following code to make some cubes dance around:
The FBX file produced by this code can be opened directly in the Hololens app 3D Viewer (I just move my fbx files into a folder sync’d to onedrive to make it easy to access them on Hololens).
How about something a little more interesting: arranging a subset of the collection in a line. From here I hope you can use some imagination on how you could tie this in with data retrieval and visualization.
For Annalect Lab’s minimum viable hologram, we’re interested in visualizations of populations, and talking about subsets. So I’ll adjust the previous code to use meshes representing people. There’s a million ways to make meshes, but there’s a tool perfectly suited for my task:
I won’t say much about MakeHuman cause I think it’s pretty intuitive. You can customize everything about your character and use some pre-loaded outfits and poses, and then export the mesh as a .obj. To make it easy on myself I saved these obj files (man.obj, woman.obj) in the same directory I’ll output my animations. Now, these objs are made up of multiple meshes, and are fairly high resolution so there’s a lot of code to work through modifying them and reducing the poly-count to get to an acceptable file size for the default FBX file viewer on hololens, but the result is a lot of fun:
The main flow of the program is like this:
Import an object, which will select all 4 meshes of that object and join them.
Decimate the mesh so it isn’t so high resolution.
Create copies of each mesh.
Create an array of x,y coordinates along a normal distribution.
Loop through an array of all the objects and set their location to the next random coordinate.
Select the first 5 objects in the shuffled array and set their keyframes to animate them as they move into a line elevated from the group.
Do the same with the next 5 objects, but to the other side of the plane.
Save a .blend file and a .fbx animation to move to Hololens.
This is my first few days using the python API to blender, so there’s surely a better way to make all the selections and de-selections, and if you know how please let me in on it! In any case, I hope this gives you a glimpse over the kind of scripted animations Blender can help you with, and there’s a million other things in the docs I haven’t touched yet. In the future I’ll have some examples of how to hook these animations up to pandas dataframes for dealing with data retrieved from SQL queries :D
Ready to get started?
Here’s a guide to setting up your blender and python environment: