Hi
Trying to draw a snail cam crv with tangent crv´s to each other, but cant for the life of me figure it out.
Crv no2 should be tangent to the inner circle (no1), crv no3 should be tangent to no2, crv no4 should be tangent to crv no3, crv no5 should be tangent to crv no4 and the outer circle no6…
Is there a way to do this? The “Flat spiral” cmd dont get tangent to the inner circle (no1).
Any help would be nice!
Per
Ooops forgot to attach the image!
Nobody? Would really need some help with this! Tried to make it in Fusion but I cant say I like that software as much as I love Rhino. But there is nothing like Fusions constraints in Rhino is there?
Hi Per - it’s always best to post a file with the inputs and what you have so far.
-Pascal
Hi Pascal! Thought it was sufficient with the screendump, but here is the file also!
SnailCamCrv_2.3dm (196.0 KB)
And never mind the straight lines, its just guides…
What you are trying to make is not a true spiral. A spiral would not be tangent to the large and small circles (curves 1 and 6) at the start and end. So what you want will look something like a spiral that is distorted at the beginning and the end.
One way to do that would be to create the tangent lines at the 6 points and then use blend curve to make the 4 segments of the spiral. After making the first blend curve make the second using the end of the first and the next tangent line.
In the picture below the red lines are the tangent lines I created and the purple are the blend curves.
You can then turn on control points and curvature graph and use scale3d on the control points in the curves to make the curves match for curvature at the ends.
spiral.3dm (105.2 KB)
I made a 1 turn flat spiral, rebuilt the curve with 13 points, then adjusted the start and end tangents manually. It’s smooth and goes pretty closely through the points, but it is not tangent to the XY axes at the other quarter points… Otherwise, jim’s method with 4 blend curves and helper tangent lines is another way to do this.
SpiralCam.3dm (1.6 MB)
Jim and Mitch, thank you for input! I like both of your ideas! Mitch, I know that the crv wont be tangent to the x and y-axis but I had problems because I started with 3-point arcs and somehow thought that I could make the next arc tangent to the arc before. Arcs are not the way to go so thank you both of you for your solutions! I will try them both, but they are both nice curves and will fulfill my purpose!
Happy Easter to you!
Per
