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Planes & Slicing Tutorial

This tutorial shows how to add crystallographic planes to the 3D viewport and use them to reveal interior cross-sections of a crystal.

Prerequisites

  • CGAspects is open with an XYZ crystal loaded
  • Lattice parameters are set (if using Miller indices)

Part 1 — Adding a Plane by Miller Indices

  1. Open Crystallography → Set Lattice Parameters and enter your unit cell parameters if not already set
  2. Open Crystallography → Add Planes (Ctrl+Shift+L)
  3. In the dialog, select the Miller coordinate mode (top selector)
  4. Enter h=1, k=0, l=0 in the index fields
  5. Set Size to 1.5× for a plane slightly larger than the crystal
  6. Leave Opacity at 180 (semi-transparent)
  7. Click Add Plane

The (100) plane appears in the viewport as a semi-transparent coloured quad.

Tip

Use the Reduce button to simplify indices. For example, entering 2 0 0 and clicking Reduce gives 1 0 0.

Part 2 — Finding a Plane from Selected Points

You can fit a plane to three or more points that you Shift+Click in the viewport:

  1. In the Planes dialog, click Find Plane
  2. The dialog closes temporarily. Shift+Click on 3 or more points in the viewport that you know lie on the same crystallographic plane
  3. A small toolbar appears — click Confirm
  4. The fitted plane is added to the plane list

This is useful for identifying unknown planes or verifying that features lie on the expected crystallographic face.

Part 3 — Slicing the Crystal

Now enable slicing to reveal an interior cross-section:

  1. In the Planes dialog, select the (100) plane you added in Part 1
  2. In the Slicing section at the bottom, check Enable slice
  3. Make sure Two-sided slab is checked
  4. Set Thickness to 10 (Å or whatever unit your crystal uses)

The point cloud clips to a slab 10 units wide around the (100) plane, revealing the crystal interior.

Part 4 — Moving the Slice Through the Crystal

  1. With the (100) plane selected, click Move Along Normal…
  2. A slider dialog opens
  3. Drag the slider left and right — the plane (and its slice) moves through the crystal in real time
  4. Pause at any cross-section that reveals interesting interior structure

Part 5 — Half-Space Mode

To show only one side of the crystal (instead of a slab):

  1. Select the plane in the list
  2. Uncheck Two-sided slab
  3. Increase Thickness to a large value (e.g., 1000) to see everything on one side

The crystal is now clipped at the plane, showing only the positive-normal half.

Part 6 — Hiding the Plane Quad

If the plane polygon obscures the view of the slice:

  1. Select the plane in the list
  2. Click Hide Plane

The coloured quad disappears, but the slice remains active. Click Show Plane to restore it.

Part 7 — Multiple Simultaneous Slices

Add a second plane perpendicular to the first:

  1. In the Planes dialog, add a new plane with h=0, k=1, l=0 (the (010) plane)
  2. Enable slice on this plane too
  3. Set Thickness to 10

Now only points that are within 10 units of both planes are shown — a box-shaped cross-section at the intersection.

Summary

Action Result
Add plane (Miller) Semi-transparent quad at that crystallographic face
Enable slice Clips point cloud to plane region
Two-sided slab Shows ±thickness/2 around the plane
Half-space Shows only one side of the plane
Move Along Normal Sweep the slice through the crystal
Hide Plane Invisible plane, active slice
Multiple slices All slices applied simultaneously (AND logic)