Hi Chris - see this clip -
http://screencast.com/t/vn23MAB0
The vertical line is changed to degree 3 to give it more points with smooth transitions. This curve is then used as a control for CageEdit on the vertical spiral. You’ll need a second vertical line to loft to if you want to do the next step.
-Pascal
Ahh … very slick! So basically, you use the line as the cage-edit entity, and it’s nodes act as change points.
When stretching the spiral into a helix, I can’t figure out how to match the spiral revs to specific points on the control line. For example: Take a spiral w/4 revs. Take a line w/4 control points. The spiral begins at one end of the line, and ends on the other end of the line. The intermediate 2 revs get located sequentially on the 2 inbetween control points. How do I accomplish that?
Hi Chris - for four turns you get three intermediate turns, right? the spiral crosses the axis three times plus the top and bottom points - so change degree to 4 on the line and you’ll see there is a control point at each turn plus the ends, 5 total - that might be what you want, however moving the points on the control curve does not necessarily keep them lined up to the same ‘level’ on the spiral. Anyway see how that works for what you need.
-Pascal
For a linear change in patch use a degree line 2. Use Line to create a degree 1 center line. Then Rebuild as Degree 2 with 3 Points. This puts one point in the center. Use the line as the control in CageEdit and move the center control point along the line until you have the desired linear pitch distribution.
Yeah- that is nice - and if you add a couple of knots (InsertKnot, Automatic twice, or Rebuild degree 2/ five points) you can get a point per turn that tracks better than the degree 4 curve.
-Pascal
Thanx for all the verbal help.
I finally saw that Pascal posted a video for me to watch.
Thanx!
Let me watch it and see if I can duplicate it.
Then I’ll get back to you.
See attached what I did.
Is there a way to get the spiral to locate on the nodes of the control line (axis/cl)?
I want to be able to get absolute control over the geometry._Wireframe-CementMixerDrum1a.3dm (514.0 KB)
Hi Chris - maybe, by fiddling … try:
-Pascal
Thanx Pascal.
Good enough is not good enough (lol) for my needs. I need precision.
Question:
If the Rail 1 profiles are not exactly aligned w/the helix Guide Curve, what will be the change in geometry when the profiles are swept, per my 3dm file?
Check my model, and you will see that the profiles are exactly where I want them, but the spiral is ‘eye-balled’ to be where it should be.
How close will the profiles shapes be, compared to if they are precisely located (if that were possible)?
Thanx …
Hi Chris - a Sweep of the curves that hit the spiral with ‘Roadlike Front’ may be what you are looking for - you can Join the leg onto the long piece and sweep both at once. Or, looking at the curves on the Spiral layer - assuming those are the ones you want to use, a Sweep2 of a line joining the ends may be OK - trim the excess with the outer drum surface? Does the attached file have the right surfaces? Sweep2 for the wider surface, AddSlash used to true up according to your other placed profiles. The shorter surface is a Sweep1 on the edge of the larger one, then Joined. Are we coming at all close?
FlightPG.3dm (236.1 KB)
-Pascal
Pascal,
Thanx for your further input.
That’s close to what I did.
Basically, I used Rail 1 for the larger helix, then trimmed it’s od and id w/the revolved surfaces. Then I used IntersectionSurfaces to create the path for Rail 1 to make the inner helix. Thing that made it ‘clean’ is I made sure to put my profiles on construction planes that are perpendicular to the point where they join the helix.
What I’d like to nail-down is a precise way to locate the pitch changes.
Is there any way to do that?