Quick tutorial - How to make an helix or spiral curve

 From:  tyglik
277.34 In reply to 277.29 
No, Pilou.

Let's summarize...
We have discussed four basic method how to create helix using the Transform/Array-Circular command.

1) Bernard's method
input: one point
- create a points by Array-Circular command with vertical step option
- start the Through-Points command and make a helix by picking each point
result: one curve with slightly different curvature at the ends

2) Loft method
input: one line
- create a lines by Array-Circular command with vertical step option
- select the lines
- start the Loft command and make a surface
- extract edge of surface
result: one curve with slightly different curvature at the ends

3) Schbeurd-Shorty spiral..... ch ch
input: one point
- create a points for only one turn of helix by Array-Circular
command with vertical step option
- copy an extra points at the ends (see 277.13)
- start the Through-Points command and make a turn of the helix by picking each point
- make multiple copies of this curve, and align them "end to end to end..." (see again 277.13)
- select the curves
- run the Join command
result: one segmented curve (a polycurve with G1 continuity between segments)

4) Pilou's arc method
input: one point
- create three point by Array-Circular
- make an arc from this point
- start the Array-Circular command and create appropriate number of copies of arc
- select the arcs
- run the Join command
result: one segmented curve (a wobbled polycurve with G0 continuity between segments)

Let's assume that we want to make a spring for each one of the helix, so we draw a circle and sweep the circle along the helix using Sweep command to create a "pipeline".
result:
- one object - the pipeline - for 1) and 2) method
- a lot of objects - segments of pipeline - for 3) and 4) method;
moreover, the segmets can not be connected together by Join
command! (it strange for G1 continuity, though).

When we create a surface using two circles as profile curves, we get one object for 3) and 4) method as well. However, it is better to choose the "flat" mode of twist option when sweep this "type of helix". (Just try selecting a seam of pipeline and you understand why).


I hope that it is as clear as day now.

Petr