The impossible triangle — also called the Penrose triangle — is one of the most mind-bending drawings you will ever make. It looks like a solid 3D triangular beam but physically could never exist in the real world. Once you understand the trick, you can draw a convincing impossible triangle in under five minutes. Parikshet breaks the method into clear steps anyone can follow.

🖍️ What You Need

  • Pencil and eraser
  • Ruler (essential — irregular spacing breaks the illusion)
  • Black pen or fine marker
  • Grey pencil or marker for shading the depth faces

How to Draw the Impossible Triangle Step by Step

  1. Draw an equilateral triangle guideline — use a ruler. All three sides must be equal length for the illusion to work properly.
  2. Draw a parallel inner triangle — inside the first, draw a second smaller triangle, pointing the same direction, about one-third the size of the outer triangle.
  3. Connect corresponding corners — draw a line from each corner of the outer triangle to the corresponding corner of the inner triangle. You now have three parallelogram-shaped beams.
  4. Identify the three square-section beams — each beam has a top face, a front face, and an inside face. Mentally trace each beam to understand the structure before continuing.
  5. Add the beam thickness lines — on each side, draw a line parallel to the outer edge and offset inward. This defines the top face of each beam.
  6. Create the impossible junction at each corner — at each corner, one beam appears to pass BEHIND another. Erase the hidden part of the beam that would be covered. This is the key step that creates the paradox.
  7. Shade the three faces — use three different tones for the three visible faces: light for the top face, medium for the front face, dark for the inside face. Consistent lighting makes the illusion fully convincing.
💡 Parikshet's Tip: The impossible junction at each corner is where the magic happens. At each of the three corners, carefully erase just the section of one beam that appears to pass behind the other. If you get all three corners right, the eye will try to follow the beams and get confused — that confusion is the illusion.

🌟 Did You Know?

The impossible triangle was created by Swedish artist Oscar Reutersvärd in 1934 and later independently by mathematician Roger Penrose in 1958. Penrose and his father published it in a psychology journal as an example of 'impossible objects'. The artist M.C. Escher then used it as inspiration for his famous impossible waterfall lithograph.

How the Illusion Works

Our brains interpret 2D drawings as 3D objects by reading visual cues — perspective lines, shading, overlapping shapes. The impossible triangle provides internally consistent cues at every local point (each corner looks physically possible on its own) but contradicts itself when you trace the whole figure. Your brain simultaneously tries to interpret it as 3D and fails, creating the sensation of impossibility.

Key insight: the illusion only works when viewed straight-on from a specific angle. A real physical model of the impossible triangle does exist — made from three separate bars aligned so that from exactly one viewpoint they appear to form a closed triangle.

🎯 Try This: Draw the Impossible Staircase

  1. Draw a square in the centre of your page.
  2. On each side of the square, draw a staircase going in the same clockwise direction.
  3. Connect the staircases at each corner so the stairs flow continuously.
  4. Shade alternate steps. The result: a staircase that descends forever with no beginning and no end — the Penrose stairs.