# How to model a frustum with specific radii?

I'm working on a maths assignment and I need to create a frustum (cone section). My first thought was to use a cylinder, but I'm unsure how to do it. So, could anyone explain, step by step, how to make such an object?

• By frustrum you mean this? I would recommend using a cube and scaling one face Commented May 28, 2015 at 1:42
• – user1853
Commented May 28, 2015 at 2:07

Press ShiftA and choose Add Cone:

Press T to show the Tool tab.

The Radius 2 will allow you to make the top flat.

Radius 1 is the base radius, and Depth will determine it's height.

Another option to access the tool's proerties is by pressing F6

You can also click the Add menu in 3D View, then click Mesh, then click Cone.

After you create the object the options to change the default appearance. However after you edit another object, you can't get back to those first settings.

Editing the mesh to change the radii would be one option.

• press the T key to show the panel or press F6
– user1853
Commented May 29, 2015 at 1:42
• this question should help blender.stackexchange.com/q/23037/2217 Commented May 29, 2015 at 1:46

It's probably better to use the cone primitive as a base, as you can have "more" control on the radii, but you can use a cylinder. Basically, you press Shift + A > Mesh > Cylinder and then in Edit Mode use Alt + RMB (or LMB, depending on which you use to select), while hovering over one of the edge loops on the base of the cylinder, to select it. Then you can use S to scale the selected vertices, followed by Enter to confirm.

If you want to control the radii numerically, you can: right after adding the cylinder, in the Toolbar (press T to toggle it) set the radius appropriately; then, while scaling one of the bases, when the scale transform is still active (i.e. after pressing S, but before confirming) you can enter numbers, in order to control the scaling - it multiplies what it was previously by what you entered.