Follow Me -- Profile Twisting

Just building a little model -- it's for a walk-through in a magazine -- and wanted to extrude a semi-circular-profile handrail on a spiral stair using Follow Me.

It starts out OK, but as the extrusion progresses, I notice that the profile twists through about 45 deg. as it goes.

Is there any way around this? (Other than using a circular handrail).

TIA,

Hi Tim

Sorry but !!

In a word NO!

You will have to build this sort of thing outside of SU.

No one here seems to be able to Ruby this twist bug yet.

Google SU should have fixed this as part of the sandbox.

A no-twist followMe would be a really usefull tool without a doubt.

TurboCad will do this easy, and you could find an old version 9-10 or such

that would be pretty cheap to buy.

dtr

Cheers, dtr.

Ah, bugger. Twisting handrails to add to my flickering shadows, OpenGL errors, spontaneously reversing faces...

In a 'trajectory' like helix, the 'z' coordinate of 'Origin' of actual 'Follow Me' process is maintaining the same level (constant 'z'). To have no a 'twist' distortion we have to have a vertical progresive (dynamic) origin (center), accompanying the face that is extruded!Once more "sorry"!

Tim,

You can build a segment of that rail (for one step) and replicate it... (See below, please)!

Hi Tim, hi folks.

In a word, YES.

See attached SU file for ideas.

Spiral_handrail2.skp

Hah! Trop cool, Jean. Trop, trop cool.

Unfortunately also trop difficile for the intended audience. We'll just have to fudge it and use a circular handrail.

Also, for give my ignorance, but how do you set the single construction point in the middle of the circle?

Usually I make components out of steps. if a rail is part of that component - all old problems are gone (new once come in but not as big)

Here's a method using multiple helices. It's similar to the method used to make a square handrail Helix + Follow Me.

If a mix of front/back faces appear with the above method, I have had good success using Orient Faces with Hidden Geometry - only need to point to a face with the right side and choose Orient Faces. All connecting geometry becomes the same side up.

To untwist a Follow Me profile, turn on hidden geometry if things have been soften. Select just the lines that make the edge of the segment/face breaks. Then use the rotate tool to untwist the selection.

EDIT: There is a new feature to the Space Design Plus plugin that does flat pattern extrusion - http://forums.renderplus.com/wiki/index.php?title=Flat_Path_Extrusion [dead link. plugins Follow Me and Keep and Eneroth Upright Extruder work.]

Try downloading any NURBS editor, they will be able to do a 1 rail sweep with no difficulty, then just export that object as a .3ds and import into sketchup.