I have a path for the outline of a gear shifter, and was wondering how I could ‘spin’ or ‘lathe’ it around its central axis to create a 3D object?
The answer is bevOb. You can use the profile as a bevel object of a curveCircle for instance. Search for additional information. You ought to be able to find some examples. The wiki can be useful as well.
Creating a circle and bevelling it with the outline gives me donut with the outilne as its cross-section, however I can scale the circle down to the smallest possible size and that problem is reduced to that size. 
(I consider that a bit of a hack, is there a better way?) I also had to remove one side of the outline so that I didn’t have two layers of mesh.
But all the normals of the resulting mesh are pointing inwards. How can I reverse them without converting it to a mesh?
Convert it to mesh. Go to object mode, select the path, then press spacebar>object> convert object type>mesh. Then, do a spin. Remember to set it smooth after, and click “rem doubl” So you don’t get a crease. I do that all the time. Hope that helps.
That works well, but if I convert it to a mesh I loose the ability to easily edit the original path. I have to select rings of verticies and translate/scale. Also with having it as a mesh, there is a pole at the top and bottom connected by 3 edged poles, and this doesn not subsurf very well. (makes a point/bumps at each of these poles)
However the final object will consist of different materials (or maybe one with a big specularity and color map?) so does the final object have to be a mesh in order to do this?
Hmm, never considered that before. It probably would need to be a mesh in the end to have vertex groups and stuff for texturing. As for the editing part, wouldn’t you do all the editing first, THEN convert it and spin it? If I had to guess, I would say you are making a light bulb, I doubt you will need to edit it again after spinning. Or is it not a light bulb?
LOL If you read my original post you’ll find it’s the top of a gear shift. It will look a little something like this. I could just have a single material with textures mapped to specularity, color and normals, to give the effect of there being different materials on different parts. Wouldn’t this allow me to not turn it into a mesh?
Ah, my mistake:p
Adding all those maps will be easy if you make them with vectors, and simply shift the colours to suit each map.
What do you mean? 
Schalken,
Set it up as follows. Create a single object that has a single edge, 2 verts connected. The edge in this object should represent the axis of interest. In object mode, click on Center New, so that the center of the object will lie on the axis.
In edit mode, (edge), select the edge that represents the axis. Still in edit mode, align the view to selected (either spacebar…view…align view…align view to selected, or numpad *).
Now, tab back to object mode and press shift s…cursor to selection. Now select the object that you want to spin, tab into edit mode and spin the selection.
Best of Luck!
In case you really want to use mesh, one option would be to use an array modifier on mesh profile. You also need an empty with rotation as the offset object.
Actually the answer is TaperOb, not BevOb 
Bevel controls the shape of the surface across the cross-section, taper controls the shape along its length.
See here for a demo file: http://mke3.net/blender/etc/lightbulb.blend
Nope, this doesn’t work. The array modifier just merges overlapping vertices, it doesn’t actually bridge faces between line segments. I keep wishing for someone to make a simple ‘Lathe’ modifier, it should be extremely easy for anyone who knows a little about rotation/matrices. I attempted it but I really don’t understand the maths behind it so I was just stabbing blind in the dark.
Yes, I could use TaperOb on a path that is the axis, or I could use BevOb on a path that is a circle around that axis (and set the width to compesate for the circle’s radius). Both work, and I have a nice shape done with the latter method, with normals pointing in the right direction, and holes in the top and bottom filled.
Now I just want to know if I can keep it as a path to do the materials (with different parts glass, metal and leather), without converting it to a mesh first.
Ah yes, you can indeed do it that way with BevOb, I stand corrected. Interesting, it’s not as immediately logical only works along straight axes, but it does allow concavity and caps the ends nicely.
As for multiple materials, I doubt it.
Nope, this doesn’t work. The array modifier just merges overlapping vertices, it doesn’t actually bridge faces between line segments. I keep wishing for someone to make a simple ‘Lathe’ modifier, it should be extremely easy for anyone who knows a little about rotation/matrices. I attempted it but I really don’t understand the maths behind it so I was just stabbing blind in the dark.
Lathe modifier is a really nice idea! I will keep that in mind. With the array modifier solution I was referring to something like this: http://wiki.blender.org/index.php/Manual/Array_Modifier#Cog .
1 Like