Mfnnurbscurve And Tangents

[eapgane]

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Hi,

I have a problem with getting the tangent vector on a curve in Maya using the Maya API. I have a point on the curve for which I get the param value using :

lStatus = lCurveFn.getParamAtPoint( lPointonCurve, lParam, lSpace );
This returns MStatus::kSuccess. lPointonCurve is the first point on the curve found out a distance of 0 from the curve's start.

I then try to get the tangent of that point by calling :
lTangent = lCurveFn.tangent(lParam, MSpace::kWorld, &lStatus );
This also returns MStatus::kSuccess.

But the tangent vector is nearly null ( 0, 0, 6 * 10 ^-13). I can't quite understand why that is.

That code seems to work on simple splines but not on the curves generated by our internal tools. I can't spot anything obvious that would make it break though.

Any ideas ?

Thanks,
Pascal.