Tangents to Splines

[......... :-\)\)]

Hi All,

I have two splines that define cross sections of a body at different planes
(like the lines drawings of yacht or airplane). Each of the two splines
define a shape that are approximately elliptic (actually its a conic). The
two splines are approximately concentric (i.e. one is inside the other and
they don't overlap).

On the inner spline I have drawn a tangent to the spline at some arbitrary
point.

The problem I am I am trying to solve is how to find the point at which a
second tangent intersects the outer spline when the second tangent is
parallel to the first on the inner spline.

Anyone got any ideas ??

Thanks,

Steve
tdfsksHATESPAM@yahoo.com
Remove the HATESPAM to email direct ...

PS: I can send the ACAD file to anyone who needs it to visualise the
problem.

[......... :-\)\)]

I have had a number of suggestions my direct email to draw a line from the
point of tangency on the first curve as a perpendicular to the second curve.

This produces a tangent which is close but not exact. Unfortunately this is
not good enough in this case.

The exact tangent could be found by a slight variation of this approach but
unfortunately I cannot figure out how to do this.

A line passing through both tangents such that it is perpendicular to one
must also be perpendicular to the other (remember the tangents are
parallel). The suggested approach ends up with a line that is perpendicular
to only one tangent. In general such a line can only pass through one of the
points of tangency. A line joining both points of tangency will have an
angle to both tangents other than 90 deg.

However if I could draw a line with a deferred perpendicular from the first
tangent to a point on the second tangent that is perpendicular with the
spline then this would give the right point on the second spline. However I
cannot make this work .... perhaps the maths cannot be solved hence ACAD
does not give the option.

The second possibility is to draw a tangent to the second spline with a
deferred tangency condition. I then need to find a way to force this second
tangent to be parallel to the first. I cannot see a way to do this either
.......

Further suggestions are welcome ...

Thanks,

Steve


"......... :-))" <smjmitchellHATESPAM@yahoo.com> wrote in message
news:431cf4f9$0$17734$afc38c87@news.optusnet.com.au... Hi All, I have two splines that define cross sections of a body at different
planes (like the lines drawings of yacht or airplane). Each of the two splines define a shape that are approximately elliptic (actually its a conic). The two splines are approximately concentric (i.e. one is inside the other and they don't overlap). On the inner spline I have drawn a tangent to the spline at some arbitrary point. The problem I am I am trying to solve is how to find the point at which a second tangent intersects the outer spline when the second tangent is parallel to the first on the inner spline. Anyone got any ideas ?? Thanks, Steve tdfsksHATESPAM@yahoo.com Remove the HATESPAM to email direct ... PS: I can send the ACAD file to anyone who needs it to visualise the problem.