I'm working in the SageMath Cloud. The code block
x,y,t = var('x,y,t')
f = lambda x,y: x*abs(y)/sqrt(x^2+y^2) if (x,y)<>(0,0) else 0
a,b = 1,6
e = 0.1
parametric_plot3d( [b*t, -a*t, f(b*t,-a*t)], [t,-e,e], color="yellow", size=15 )
produces an error message:
error rendering 3d scene -- error downloading /blobs/682b952d-d577-45ce-98ff-4e7a06ddad32.sage3d?uuid=682b952d-d577-45ce-98ff-4e7a06ddad32
But if I change the fourth line to e = 1, then it works just fine.
A similar error was reported in http://ask.sagemath.org/question/27300/error-rending-3d-scene, but the fix there was easier.
