A hopper, a length of reducing duct, a pier that is wide at the base and narrow at the top. What they share is two ends with different cross sections, and a middle that has to change gradually from one to the other.
The loft command in AutoCAD produces exactly that middle. This article copies the prompt sequence verbatim, checks the volume of the solid against the formula for a frustum, and sets out the error message everybody meets on their first attempt. For the whole three-dimensional toolkit see our AutoCAD for Construction course.
Where to start it
Read straight out of the acad.cuix interface file of the 2027 release.
| Way in | What to use |
|---|---|
| Full command | LOFT |
| Alias | none |
| Ribbon | none |
| Classic menu | Draw → Modeling → Loft |
| Toolbar | Modeling → Loft |
Two empty rows explain why people can use AutoCAD for years without ever typing this one. It has no alias, and the ribbon of the default workspace carries no button for it. To get a button you have to switch on the Modeling toolbar or bring back the classic menus, which is covered in our article on the AutoCAD interface.
Three relatives, from the same file:
| Command | Alias | Menu |
|---|---|---|
EXTRUDE | EXT | Draw → Modeling → Extrude |
REVOLVE | REV | Draw → Modeling → Revolve |
SWEEP | none | Draw → Modeling → Sweep |
The steps on the command line
Copied verbatim from AutoCAD 2027.
Command: LOFT
Current wire frame density: ISOLINES=8, Closed profiles creation mode = Solid
Select cross sections in lofting order or [POint/Join multiple edges/MOde]: 1 found
Select cross sections in lofting order or [POint/Join multiple edges/MOde]: 1 found, 2 total
Select cross sections in lofting order or [POint/Join multiple edges/MOde]:
Enter an option [Guides/Path/Cross sections only/Settings] <Cross sections only>:| Step | What it asks | What you do |
|---|---|---|
| 1 | Select cross sections in lofting order or [POint/Join multiple edges/MOde]: | Pick the first cross section |
| 2 | the same prompt again | Pick the second, then Enter |
| 3 | Enter an option [Guides/Path/Cross sections only/Settings] <Cross sections only>: | Enter to take the default |
The two words that matter most are in step one: in lofting order. The program joins the sections in the order you pick them, not in the order they sit in space. Pick them out of order and the solid twists in a way that makes no sense at first sight — this is far and away the commonest cause of a model that looks wrung out.
The error everybody meets once
Pick one cross section and press Enter, and the program answers with a single line:
At least two profiles must be selected.The wording is plain enough: the command wants two cross sections as a minimum. If you only have one shape and want it to close down to a point — modelling a cone, say — use the POint option at step one and nominate the apex as the second section. Autodesk describes that option as "Specifies first or last point of the lofting operation. If you start with the Point option, you must next select a closed curve."
The volume matches the formula exactly
This is the surest way to know whether what you made is right.
Take two circles of radius 300 and 150 and set them 800 apart vertically. Joining them has to produce a frustum, and a frustum has a volume formula ready to hand:
| Value | |
|---|---|
| Volume read off the solid | 131,946,891.45 |
| By hand, π·h/3·(R² + R·r + r²) | 131,946,891.45 |
| Difference | 0.000000% |
Not one part in a million out. So the program is not drawing something that merely looks right: it builds the true straight transition between the two circles, and what it makes is a genuine solid rather than a hollow shell. A shell would have given a quite different figure.
The same check works on any model that arrives from elsewhere: select the solid, open the Properties palette, read the volume and compare it with your own sum. That palette is covered in our article on the Properties palette in AutoCAD.
Joining two cross sections in the right order
This is what decides whether the result is clean or ugly, and almost no tutorial covers it.
Besides the picking order there is a second thing governing the shape: the start point of each section. With circles it never bites, because a circle is symmetrical. But with two rectangles, two polylines or two arbitrary shapes the program has to pair up a vertex on one with a vertex on the other. Pair them one vertex out and the solid twists immediately.
That is what the Guides option is for. Autodesk describes it as "Specifies guide curves that control the shape of the lofted solid or surface." In practice: draw a few lines running straight from a vertex on the lower section to the matching vertex on the upper one, then nominate those as guide curves. The program follows them when pairing up, and the twist disappears.
Where the sections need to be closed polylines, join the loose linework first — covered in our article on polylines in AutoCAD.
The four options at the last step
Step three offers four. The descriptions below are taken from Autodesk's LOFT page.
| Option | What Autodesk says | When to use it |
|---|---|---|
Guides | "Specifies guide curves that control the shape of the lofted solid or surface." | Unsymmetrical sections, where the solid keeps twisting |
Path | "Specifies a single path for the lofted solid or surface." | When the solid must follow a curve you have drawn |
Cross sections only | "Creates lofted objects without using guides or paths." | The default, and enough for most work |
Settings | "Displays the Loft Settings dialog box." | To change how the surface transitions between sections |
The Path option carries a condition that is easy to forget: the path has to cut through the plane of every cross section. A curve drawn floating beside the stack of sections will not be accepted.
The dialog behind Settings is where the transition style lives: a surface pulled taut between sections, or one that curves smoothly. For hoppers, tapered ducts and piers, keep it straight; for hulls and thin shell roofs, let it curve.
Two more options sit at step one rather than step three, and both are worth knowing. Join multiple edges is described by Autodesk as handling "multiple, end-to-end edges as one cross section" — that is what you reach for when a section was drawn as several separate pieces and never joined into one object. MOde "Controls whether the lofted object is a solid or a surface." Left alone it follows the setting printed on the opening line, Closed profiles creation mode = Solid, which is why closed sections normally give a solid without anyone having to ask.
A solid model: loft, sweep or extrude
Four commands in the same family, and picking the wrong one makes work.
| Command | What it needs | What it makes |
|---|---|---|
EXTRUDE | a profile and a height | A straight solid of constant section |
REVOLVE | a profile and an axis | A solid of revolution |
SWEEP | a profile and a path | A solid following the path, constant section |
LOFT | several unlike sections | A solid changing gradually from one to the next |
One line to remember it by: a constant section is faster with the other three, and only a section that changes along the run needs the loft command in AutoCAD. Sweeping along a path is covered in our article on the sweep command in AutoCAD, and revolution in our article on the revolve command in AutoCAD.
Choosing carefully is not about tidiness. Each command writes a different kind of object into the drawing, and that governs how easy the model is to change later. A straight length of duct made with EXTRUDE can have its height edited in the Properties palette in seconds; the same duct built by lofting has to be rebuilt from scratch.
Four things people say that are not true
| What people say | What the 2027 release actually does |
|---|---|
| The command has a ribbon button | No button and no alias; only the menu and the Modeling toolbar |
| One section is enough | The program answers At least two profiles must be selected. |
| It sorts the sections out for you | The prompt says in lofting order — your picking order is the order |
| Open or closed, a section gives a solid | The first line reads Closed profiles creation mode = Solid; an open section gives a surface |
Frequently asked questions
Is there an alias?
No. Type the whole word LOFT, or use Draw → Modeling → Loft.
Why does it say "At least two profiles must be selected"?
Because only one section was picked. The command needs at least two. With a single shape that should close down to a point, use the POint option.
The solid came out twisted — how do I fix it?
Either the picking order was wrong or the start points of the two sections do not correspond. Draw lines joining the matching vertices and nominate them under Guides.
How do I model a frustum?
Run this command on two circles of different radius. The volume comes out exactly as π·h/3·(R² + R·r + r²) predicts.
How many sections can it take at once?
There is no upper limit, as long as there are at least two. Pick them in order from one end to the other, then press Enter.
What kinds of object work as sections?
Per Autodesk: 2D polyline, 2D solid, 3D spline, arc, circle, ellipse, elliptical arc, helix, line, region, a planar or non-planar face of a solid, and points — though a point may only be the first or last section.