# How to define the diameter to a certain size

I have made a 3d curved cylinder in blender, Inlet diameter of cylinder is certain size, say: 25 meters and outlet diameter of cylinder is say: 7 meters, I want resize or define inlet dia to 0.95 mm and outlet diameter to 0.75 mm, is it possible to do it in Blender?

• Could you add an example of what you want to achieve
– VRM
Mar 17 '15 at 21:16
• you can't, your best bet is the proportional editing which result will depend on the cylinder shape, it would be better if you create it with a curve modifier ( you could easily edit the original then apply the modifier ) Mar 17 '15 at 22:49

Using curve objects in blender you can set the size of the extruded shell that follows the curve and also adjust it along the path as desired.

There are two ways to turn a curve into a tube. For a quick circular bevel, just set the bevel depth and resolution for the curve, you will also want the fill to be set to full. The other way is to use another curve object to define the outer shape of the bevel.

The bevel depth is radius in blender units of the extrusion. If you use a bevel object then the size of the object used will determine the size of the extrusion.

Each point on a curve has a Radius property. At 1.0 the extrusion will match the bevel size set at that point. Other values will reduce or increase the size, so a point having a radius of 0.25 will be 1/4 the size of the main "pipe".

You can find the radius property in the properties sidebar T under Transform while editing a curve. You can also use ⎇ AltS to change the size interactively. A linear falloff is used between each points radius.

So once you set the main size in the bevel size, to adjust the size of specific points you will need to do a little calculation which can be done while entering the value to use. For example if you have the main bevel set to 0.95 and want 0.75 at a given point, in the radius enter .75/.95 and it will calculate the radius of .789 that you want.

• Thanks for this answer, do you know how to get back to this panel after I've already applied and deselected the path? Dec 22 '16 at 21:49
• Nevermind, I found it under the NurbsPath data tab of the inspector. Dec 23 '16 at 2:17