DIY Hologram Pyramid: Build One with Just a Smartphone and Plastic
A hologram pyramid — sometimes called a Pepper's Ghost pyramid — is one of the most satisfying craft projects in the maker community. Built from nothing more than a piece of clear plastic and a smartphone, it transforms a flat screen into what appears to be a glowing three-dimensional figure floating in mid-air. The physics is a 19th-century stage illusion, but the effect is genuinely striking. This guide gives you everything you need to build one and set it up with HoloPath.
How It Works
The pyramid sits over your phone screen, which plays a specially formatted video with four copies of the same image arranged around a black centre. Each face of the pyramid is angled at roughly 45 degrees. Light from each quadrant of the screen bounces off the corresponding face toward the viewer's eye, and because the pyramid is clear, all four reflections overlap at the centre. The result is a reflected image that appears to float inside the pyramid with no visible screen behind it — particularly convincing in a dimly lit room.
Materials You Need
- Clear PET plastic sheet, 0.5 mm to 1 mm thick — the cover from a CD jewel case works perfectly, as does an overhead projector transparency sheet or a thin plastic folder
- A ruler and fine-tipped marker or scribe
- Sharp scissors or a craft knife and cutting mat
- Clear adhesive tape, superglue gel, or a hot glue gun
- Your smartphone
Avoid glass, which is hazardous to cut and too heavy. Avoid frosted or tinted plastic, which kills the reflection. CD case covers are ideal because they are perfectly flat, optically clear, and just the right weight to hold shape without warping.
Dimensions and Cutting
Each pyramid is made from four identical trapezoid panels. The trapezoid has a short parallel edge at the top (the apex of the pyramid), a longer parallel edge at the bottom (which rests on the phone screen), and two angled sides. The key relationship is that the bottom edge equals one quarter of your phone screen's short dimension, and the height of the trapezoid is derived from the geometry of a 45-degree reflection.
For a 5-Inch Screen (approximately 62 mm wide display area)
- Top edge (apex): 10 mm
- Bottom edge: 55 mm
- Height of trapezoid: 30 mm
- The angled sides will measure approximately 32 mm each
For a 6-Inch Screen (approximately 74 mm wide display area)
- Top edge (apex): 12 mm
- Bottom edge: 65 mm
- Height of trapezoid: 36 mm
- The angled sides will measure approximately 38 mm each
Draw the trapezoid on the plastic using a ruler and marker. Score along the lines with a craft knife and snap cleanly, or cut with sharp scissors in a single smooth stroke. Cut four identical pieces. The cleaner and more precise your cuts, the better the final image quality — mismatched panels create visible seams in the reflection.
Assembly
Assemble the four panels into a truncated pyramid shape with the small edges meeting at the top and the large edges forming a square base. Hold the first two panels together at their angled sides with a small strip of clear tape on the outside edge — tape on the inside face will be visible in the reflection. Continue adding panels until all four are joined. Run a thin bead of superglue along each interior joint for rigidity, or use a hot glue gun carefully to avoid drips inside the faces. Allow to cure completely before use.
Test the fit on your phone. The base should sit flat on the screen with the four bottom edges forming a neat square centred on the display. The pyramid should be stable and not rock.
Setting Up HoloPath for Pyramid Playback
In HoloPath, select the Pyramid (4-way) layout option. This arranges four copies of your holographic GIF around a black centre square, rotated so that each face of the pyramid receives the correct orientation. Use a pure black background — any ambient light from the screen area outside your subject will wash out the reflection. Set your phone to maximum brightness and disable auto-brightness.
Play the resulting GIF full-screen on your phone in landscape or portrait orientation depending on which matches your pyramid's base orientation. Dim the room lights as much as possible. Position the pyramid over the GIF and step back slightly — the sweet spot viewing distance is roughly 20 to 40 cm from the pyramid's apex, at eye level with the tip.
Troubleshooting
Image Is Too Dim
Check that your phone is at maximum brightness. Ensure the room is as dark as possible — even a small ambient light source behind the viewer will compete with the reflection. Thinner plastic transmits light better than thicker material; if your plastic is 2 mm or more, try sourcing a thinner sheet.
Reflection Visible from Wrong Angle
The pyramid panels must be at exactly 45 degrees to the screen. If panels are tilted inward or outward, the reflected image will shift angle and appear ghosted. Rebuild the joints and use a set square to verify the panel angle before the adhesive sets.
Image Appears Doubled or Ghosted
PET plastic produces two reflections: one from each surface. Using thinner plastic minimises the gap between them. Anti-reflection coating on one surface eliminates the secondary reflection entirely — some presentation-quality transparency sheets have this coating.
Visible Seams Between Panels
Score and cut more carefully, and sand the edges lightly with fine-grit sandpaper for a tighter joint. Tape only the very outer edge of the joint to keep the reflective inner face clear.