Canvas 3d JS Library

As we are moving away from using points for now, it was time to make a demo using spheres again. Instead of just re-posting an old demo, it seemed like a good time to add in some of the features people have suggested, such as being able to move the camera (Andor had already put that in the library, I just had not taken advantage of it). Then, since the point-markers looked so nice in different colours, I thought I should keep that idea and make the sphere-markers coloured too (again, the code was already there, but I hadn’t used it), but rather than being random I decided it would be useful to group the markers into right side, left side and core (or other), much like Vicon does. It was also a good opportunity to take advantage of some of the new functionality Andor has been working on (like the gradient colours on lines).

Now, as Andor said in his previous post, spheres are much more complicated than points when it comes to rendering, so my first version of the new demo was noticeably slower than the version using points. The counter to this was to reduce the complexity of the sphere, turning it into something sphere-ish but much easier to render. Instead of the 200-odd faces in each of the original spheres, I dropped it to 64.

I experimented with some simpler spheroids, getting all the way down to 4 triangles to try to find one that is simple to render and still looks good. No, I guess a tetrahedron isn’t really a spheroid, but I thought I should try it anyway.

Here are some of the almost-spheres I put together in Google Sketchup:

64 triangles		48 triangles
24 triangles		18 triangles
4 triangles

The one with 48 triangles seems to look the most sphere-like overall (it doesn’t have the flat top of the 64 triangle object), so I decided to go with that for now.

Now to finish off the tool that creates the templates used to determine which markers should have lines drawn between them. It as almost working, but it is losing track of which marker is which somewhere. For example, while it might think it is putting a line between the left forearm and left elbow (which it should be), it is actually connecting the C7 vertebrae to the right knee (which I imagine would be rather painful).

UPDATE: I borrowed some more of Andor’s code to add better lighting to the scene and now the semi-spheres look much better.