6.4. SUMA Clipping Planes


To utilize this functionality, your system’s AFNI version should be at least 21.1.13.


This page is a work in progress.

6.4.1. Introduction

Visualizing surface data is great. But sometimes, you might want to focus on just part of the data, or to look at nested layers. In these cases (and others), it can be useful to have clipping planes: these are geometrically flat planes that clip away data on one side. At present, you can have up to 6 planes, each of which is mobile (translate, rotate, flip, etc.).

One particularly useful application of clipping planes is here:

6.4.2. Clipping plane cheatsheet

Enter/exit clipping plane mode with Ctrl+Shift+c. The first time one enters this mode, 1 clipping plane appears. While in clipping plane mode is active, a “C” appears in the SUMA viewer panel.

There can be up to 6 clipping planes. They are numbered [1-6], and each has a unique color (in order):

1 - Red
2 - Green
3 - Blue
4 - Cyan
5 - Magenta
6 - Yellow

Clipping planes can be scrolled (= translated) along their normals and/or rotated around their tangent or cotangent axes, using the mouse or keypresses.


[1-6] means one of the clipping plane numbers, in range [1, 6].

An active clipping plane is clipping (whether visible or not), while an inactive plane is not clipping (whether visible or not).

A selected plane can be controlled with the action keys (scroll/translate, rotate, flip/invert, etc.).

The normal of a plane is a direction perpendicular its face. Scrolling/translation is motion along either the “inner” or “outer” normal direction. The “outer” normal is side of the plane that is originally clipping.

The rotation of a plane moves it around one of the coordinate axes. Each plane can rotate around two axes. If the plane’s normal is originally parallel to the y-axis, then it can rotate around either the x- or z-axis.

On a Mac, you would likely replace the Alt keystroke with Cmd or Opt.




Toggle in and out of clipping plane mode


Toggle the numbered clipping plane on/off


Toggle all active clipping planes on or off


Reset all clipping planes (to basic starting state)


Flip/invert the clipping direction of selected plane


Toggle view of all active clipping planes on/off (active clipping remain active)


Select a clipping plane, after which it can be flipped, rotated, scrolled/translated, etc.

Alt+[up/down arrow]

Rotate a selected clipping plane around one axis (perpendicular to its normal)

Alt+[left/right arrow]

Rotate a selected clipping plane around another axis (perpendicular to its normal)

Alt+[scroll wheel]

Translate a selected clipping plane along its normal


Scroll/translate a selected clipping plane “inwards”


Scroll/translate a selected clipping plane “outwards”


Double the current scroll/rotation stepsize; can be used repeatedly to increase further.


Halve the current scroll/rotation stepsize; can be used repeatedly to decrease further.


Reset the current scroll/rotation stepsize (current defaults: 1 mm scroll, 1 deg rotation).