View Full Version : Rail extrude

10-08-2003, 12:58 PM
I wish to make pipelines that curls and bend on the outside of a cylinder-shaped object. Im planning to do this by rail extruding a poly, but i dont know how to make the splines follow the surface of the cylinder on a even distance, turning right and left on it. Please help me!

10-08-2003, 07:40 PM
perhaps you can do it with "magic bevel"!

10-09-2003, 04:12 AM
if i understand your question, you mean something like this:

10-09-2003, 04:22 AM
and this is how i did it:

* create a cylinder in a layer (24 sides, 1 segment)
* create in another layer another cylinder with 12 sides and 10 segments. the number of sides & segments depends on the length of the 'target' cylinder and the complexity of the spline you want.
* killed the polygons of the second cylinder, keeping all the points (hit 'k')
* selected the points for the path of the spline
* inversed selection to select unneeded points and killed them

now you should have all points for the path of the spline

* now use the 'stretch' tool to move the points outside the original cylinder (you may want to select the first cylinder in the background to set the right distance)
* select the points (in correct order!)
* hit the 'make curve' button and select 'make OPEN curve'
* select a new (empty) layer and set the curve layer in the background. now create a flat disc (or whatever) at the start of the curve, and hit the 'rail extrude' button, use 'automatic' and 'oriented'.

the result is something like the image shown above... note: i made a mistake selecting the path, so you can see in the view from the right that there's the path doesn't go right... selecting the points for the path takes some time...

10-09-2003, 06:52 AM
Thanks, you're a lifesawer, i'll see if that's enough. but if I want to kind of make the splines flat and then "wrap" them around my cylinder, can it be done? I need lots of precision.
You see, it's not a real cylinder, it's a lated object, maybe i wasn't clear enough. sorry.

10-09-2003, 07:01 AM
here's a screengrab

10-09-2003, 07:27 AM
just to make life easier, i came up with a less complex idea :p

* copy your object to a new (empty) layer
* keep the poly's this time (tho i deleted the inner poly's for better side / front / top view)
* use the knife tool to get some extra points to lay the path
* select the points wich make the path in the perspective viewport, this is the easiest as you won't accidently select points at the other side of your object
* cut or copy the points (hit 'x')
* empty the layer (hit 'del')
* paste the points
* now select them again, in right order of the path
* create an open curve
* rail extrude a 2D shape along the path. a disc works best 'cause you will go round some corners, a box will always spin a bit around the wrong axis somehow...

the new image:

10-09-2003, 07:31 AM
note on the image:

* at the top you'll notice the rail to "sink" into the mesh a bit. this is because i didn't had enough points wich made up the path...
* if you want the rail to be "resting" on the object, don't use the stretch tool to move the points of the path outside, but keep them on their original position...

owh, btw, thnx for calling me a lifesaver, don't hear that every day :D

10-09-2003, 08:00 AM
thatt'll do it!

well you know sometimes being a lifesaver is alot easier than one think :p