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 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
