3D rendering in tplot (diagnostics part 7)

In previous posts of this series, I covered some diagnostics improvements I’ve made to help work on more advanced gaits for the mjbots quad A1 (1, 2, 3, 4, 5, 6).  This post will cover the last major new piece of diagnostics I added to tplot2, 3d rendering of telemetry data.

3D rendering

While it should be obvious, I’ll give a little exposition.  tplot2 in its state prior to this could show a “tree view” of all data logged in numeric form.  It had a “plot view” which let you plot any single floating point scalar vs time.  As of recently, it could also render video associated with a given point in time in the log.  However, as anyone who has ever tried to debug a 3d dimensional software application, much less a 3d dimensional robot, can attest, debugging with scalar numbers and time plots is only productive for a very limited range of problems.

I’ve been wanting to extend my plotting tools with 3d rendering for some time, and now have gotten around to a minimal first pass.  The logic itself isn’t terribly complicated.  A separate GL Framebuffer object is created in order to render into a texture, then pretty standard GL vertex and fragment shaders are used to render some triangles and lines.  Initially, I’m just doing the robot body, the commanded and actual feet positions, speeds, and forces, and an estimate of the ground underneath them.

20200515-tplot2-3drender

20200515-tplot2-3drender-video

While there is a lot of room for improvement here, both in terms of the visual quality of the existing renderings, and new features that could be rendered, this is already proving itself to be invaluable in diagnosing longstanding problems with the gait motion.

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