`curve.lengthAtT(t [, opt])`

Return the length of the curve up to the point specified by `t`

.

The curve is divided at `t`

and the length of the first subcurve is returned. For more information about curve length calculation refer to `curve.length()`

documentation.

The default value for `opt.precision`

is 3; this corresponds to maximum observed error of 0.1%.

This method does make use of the `opt.subdivisions`

property.