# SECTION in AutoCAD

> How AutoCAD's SECTION (SEC) makes a region where a plane cuts 3D solids, prompt by prompt: 3points, Object, Zaxis, View, XY, YZ, ZX. Try it free online.

SECTION makes a cross-section of 3D solids: a region where a plane cuts each one, and the solids stay as they were. It asks for the solids, until Enter: as in AutoCAD 2027, a set selected before it is dropped and asked for again, what is not a solid is passed over, and a set with none says `No Solids, Surfaces or Meshes selected.`. Then the plane: by default you give three points on it, and the options give it another way, as at [`SLICE`](https://mellowcad.com/docs/commands/slice.md).

Each solid the plane cuts gets its region, lying in the plane: a block with a hole through it gives the outline with the hole's gap, a cylinder cut along its axis a rectangle. A plane on one of a solid's faces gives that face. One the plane misses says `Sectioning plane does not intersect the selected solid.`. The regions take the current layer and properties, not the solid's; [`MOVE`](https://mellowcad.com/docs/commands/move.md) takes one out to see it, [`AREA`](https://mellowcad.com/docs/commands/area.md) and [`MASSPROP`](https://mellowcad.com/docs/commands/massprop.md) measure it, and [`EXTRUDE`](https://mellowcad.com/docs/commands/extrude.md) turns it into a solid. The whole command is one undo step. MellowCAD's 3D is solids only, and still partial.

- **Command:** `SECTION`
- **Aliases:** `SEC`
- **Panel:** [Draw](https://mellowcad.com/docs/commands.md#draw)
- **Try it:** [Open the editor](/draw), type `SEC` and press Enter.

## At the command line

The engine draws it and writes its history as you would type it: the prompts in AutoCAD 2027's order, with the same option letters.

A block with a hole through it, cut by the ZX plane through the hole's centre: SECTION makes the profile, moved out in front, two rectangles with the hole's gap between.

```text
Command: SECTION
Select objects: 1 found
Select objects:
Specify first point on Section plane by [Object/Zaxis/View/XY/YZ/ZX/3points] <3points>: ZX
Specify a point on the ZX-plane <0,0,0>: 0,20,0
Command: MOVE
Select objects: 1 found
Select objects:
Specify base point or [Displacement] <Displacement>: 0,-50
Specify second point or <use first point as displacement>:
Command: -VIEW
Enter an option [Orthographic]: SEI
Regenerating model.
Command: VSCURRENT
Enter an option [2dwireframe/Hidden/Conceptual] <2dwireframe>: H
Command: ZOOM
Specify corner of window, enter a scale factor (nX or nXP), or [All/Extents/Previous/Scale/Window/Object]: 0.85x
```

## Options

### `Object` (`O`)

Takes the plane of an object you pick: a circle, an ellipse, an arc, a 2D spline or a 2D polyline.

### `Zaxis` (`Z`)

Asks for a point on the plane, then a point on its Z axis, the line square to it.

### `View` (`V`)

The plane parallel to the screen, through a point you give.

### `XY`

The UCS's XY plane, through a point you give: a point at a height makes a level section there. Enter takes the UCS's origin.

### `YZ`

The UCS's YZ plane, through a point you give; Enter takes the UCS's origin.

### `ZX`

The UCS's ZX plane, through a point you give; Enter takes the UCS's origin. The session's section is this plane through the hole's centre.

### `3points` (`3`)

Three points on the plane, which may then tilt any way. It is the first prompt's default, so a point there is the first of the three.

## What it does not do yet

Surfaces and meshes, which MellowCAD does not have. A planar 3D polyline as the plane's object, which AutoCAD takes. The cuts MellowCAD has no exact form for yet, as at [`SLICE`](https://mellowcad.com/docs/commands/slice.md), which say that one boolean operation failed. SECTIONPLANE and live sectioning, which AutoCAD's ribbon offers in SECTION's place: here SECTION is typed.

[What it does and still lacks, in detail (in English)](https://github.com/ovelilla/mellowcad/blob/main/docs/coverage/draw.md#section--sec--es-seccion--sc--pt-br-corte--secao)

## Questions

### How do I make a section of a 3D solid in AutoCAD?

Run SECTION, select the solid and press Enter, then give the plane: `ZX` and a point through the middle cuts it front to back, `XY` and a point at a height cuts it level. The region lies inside the solid: [`MOVE`](https://mellowcad.com/docs/commands/move.md) it out to see it.

### What is the difference between SECTION and SLICE?

[`SLICE`](https://mellowcad.com/docs/commands/slice.md) cuts the solid in two and keeps one part or both. SECTION leaves the solid whole and draws a region where the plane cuts it.

### What is the shortcut for SECTION in AutoCAD?

`SEC`, then Enter or Space.

### Why does SECTION say the plane does not intersect the solid?

The plane misses it: check how you gave it. `XY`, `YZ` and `ZX` are the UCS's planes, so a point at the wrong height or side puts the plane outside the solid.

## Related commands

- [SLICE in AutoCAD](https://mellowcad.com/docs/commands/slice.md)
- [REGION in AutoCAD](https://mellowcad.com/docs/commands/region.md)
- [SUBTRACT in AutoCAD](https://mellowcad.com/docs/commands/subtract.md)
- [MASSPROP in AutoCAD](https://mellowcad.com/docs/commands/massprop.md)