If you're open to using BOSL2 library:
https://github.com/BelfrySCAD/BOSL2/wiki/partitions.scad

Dan

On Tue, Nov 19, 2024 at 1:57 PM Mark Erbaugh via Discuss <
discuss@lists.openscad.org> wrote:

On 11/19/2024 5:56 AM, Mark Erbaugh via Discuss wrote:

There is no cross-section view.  You can use difference or intersection
to achieve the same effect.

Caution:  in perspective mode, the previewer doesn't like it when the
camera is inside negative space for a difference.  This is often a
problem when you're differencing away large cubes to do cut-aways.  This
program demonstrates the problem:

difference() {
    sphere(10);
    cube(1000);
}

In perspective mode, rotate the view so that the camera is looking at
the sphere from the positive-XYZ octant; observe that the cut-away
portion is restored.

I thought there was a similar effect for intersection, but I'm not
duplicating it at the moment.

What about just moving the desired x-section to XY plane and use

projection(cut=true) on that ?

Jordan Brown via Discuss discuss@lists.openscad.org schrieb am Di., 19.
Nov. 2024, 17:01:

On 11/19/2024 8:07 AM, Guenther Sohler wrote:

Indeed, if what you want is a cross-section rather than a cut-away, that
will work.  Loses color, unfortunately.

On Tue, Nov 19, 2024 at 08:56:43AM -0500, Mark Erbaugh via Discuss wrote:

Yeah. That's what I always do.

Roger. 

--
** R.E.Wolff@BitWizard.nl ** https://www.BitWizard.nl/ ** +31-15-2049110 **
**    Delftechpark 11 2628 XJ  Delft, The Netherlands.  KVK: 27239233    **
f equals m times a. When your f is steady, and your m is going down
your a** is going up.  -- Chris Hadfield about flying up the space shuttle.
**  'a' for accelleration.

This is my !start here.scad file. I now start every project with this construction. I can add a cross section in any part of my project in a few seconds. I use my own crossSection() module, but the BOSL2 equivalents could also be used with a little modification. My crossSection code is in my library, but I show it below. The include also includes BOSL2 so a single include from my lib is sufficient for most things. Obviously I add various calls to “assembly" as I build.

include <BClib/common.4.scad>

showX = false;

ex = 0;

doCrossSection = "none"; // ["none", "x", "y", "z", "-x", "-y", "-z", "polar"]
radius = 0;
phi = 0;
theta = 0;

module Customizer_Limit () {}  // This actually works

CS();

module CS() {
if (doCrossSection == "none") {
d = echo("none");
assembly();
} else if (doCrossSection == "polar") {
d = echo("polar");
crossSection(r = radius, theta = theta, phi = phi)
assembly();
} else {
d = echo(doCrossSection);
crossSection(view = doCrossSection, r = radius)
assembly();
}
}

module assembly() {
if (showX) {
sphere(50);
}
}

From my library:

/*
crossSection(view = "x", r, theta, phi, right, fwd, up)

r    - distance from origin
theta - angle of rotation in XY from +X counter clockwise
phi  - Angle from +Z, 0 == straight up
*/

module crossSection(view = "", right = 0, fwd = 0, up = 0, r = 0, theta = -1000, phi = -1000) {
if (_Help(view)) {
echo("view  - axis to view from, or alternately, to remove");
echo("r    - distance from origin");
echo("theta - angle of rotation in XY from +X counter clockwise");
echo("phi  - Angle from +Z, 0 == straight up");
}
//d = echo("crossSection ", view, r, theta, phi);

th = theta > -360 && theta < 360 ? theta
  : view == "x" ? 0
  : view == "y" ? 90
  : view == "z" ? 0
  : view == "-x" ? 180
  : view == "-y" ? -90 
  : view == "-z" ? 0 
  : 0; 
  
ph = phi >= 0 && phi <= 180 ? phi
  : view == "x" ? 90
  : view == "y" ? 90
  : view == "z" ? 0
  : view == "-x" ? 90
  : view == "-y" ? 90 
  : view == "-z" ? 180 
  : 90; 

m = r     != 0 ? r
  : right != 0 ? right  
  : fwd   != 0 ? -fwd  
  : up    != 0 ? up 
  : 0; 

//d0 = echo("crossSection ", m, th, ph);

difference() {
    union() {
        children();
    }
    moveSP(r = m, theta = th, phi = ph)
    zrot(th)
    yrot(ph)
    cube(1000, anchor = BOTTOM);
}

}

/*
moveSP(r, theta, phi)

Move Spherical

r    - distance from origin
theta - angle of rotation in XY from +X couter clockwise
phi  - Angle from +Z, 0 == straight up
*/

module moveSP(r, theta, phi) {
move(spherical_to_xyz(r, theta, phi)) children();
}