Geometry

Kinegrams: Optical Animations from Static Images

Gianni Sarcone

Two monks stood outside a temple, watching its flag wave in the wind.
“The flag moves,” said one.
“No, the wind moves,” said the other.A third monk smiled:
“Neither moves. Your mind moves.”

Back in the early 2000s, I ran a few public art workshops exploring a deceptively simple idea: a printed image does not have to move to appear animated.

The trick is a kinegram—a static image transformed into a precise pattern of lines. Place a special acetate screen over it, and the hidden movement suddenly appears.

No electronics. No screen. No animation software. Just a carefully calculated pattern and a bit of moiré.

In these workshops, we experimented with:
• concentric circles
• simple radial patterns
• geometric textures

The resulting kinegrams produce seamless, looping animations from completely static printed images. If you’re interested in exploring the technique or collaborating, feel free to contact me.

☞ More on kinegrams.

Exploring Tessellations & Op Art: Hidden Arrows

Gianni Sarcone

This brief tutorial explores an Op Art tessellation that plays with bistable perception, figure–ground reversal and negative space. By combining modular geometric tiles with contrasting colors, the pattern creates a visual interplay in which arrows can be perceived as either foreground shapes or background forms, depending on how the pattern is interpreted.

Experiment 1:

· Preparation — Fig. A: Start with a 3 × 3 square. Divide it along its diagonals into four triangles, then add a 1 × 1 square to the outer side of each triangle, as shown. Color the resulting cross-shaped tile with two contrasting colors, ensuring that adjacent sections are different colors. The construction produces four inward-pointing arrows.

· Preparation — Fig. B: Following the construction shown, subdivide a 2 × 2 square to create five diamonds arranged in a staggered pattern. Use the same two contrasting colors. This produces a complementary tile containing four outward-pointing arrows.

· Assembly — Fig. C: The two tiles are complementary and fit together. Interlock the cross-shaped tiles with inward-pointing arrows and the square tiles containing the diamond pattern to create a continuous tessellation.

Visual result: The alternating geometric modules form a large geometric Op Art pattern in which arrows emerge through figure–ground reversal. And hidden within it are, believe it or not, 100 arrows. Yes, one hundred arrows!

This op art work is available as fine art prints and canvases from my online official gallery.

Experiment 2:

· Preparation — Fig. D: Build a four-armed pinwheel shape from a 4 × 4 square, as shown.

· Assembly — Fig. E: Interlock the four-armed pinwheel shape with the cross-shaped motifs containing the inward-pointing arrows.

· Assembly — Fig. F: As shown, these four-armed pinwheel shapes can be assembled in four or more different ways, producing different geometric configurations.

Visual Result: As seen in the example below, the contrasting colors make the bright blue arrows radiating around the pink central hubs—the pinwheel shapes—stand out, while the yellow arrows, matching the background color, virtually disappear from view.

pattern with pinwheel shapes

Experiment 3:

· Preparation & Assembly — Fig. G: Combine square tiles containing interior diamond arrangements with tiles featuring four inward- and four outward-pointing arrows formed by negative space. Arrange them alternately to create a checkerboard pattern.

The example below shows a 3 × 3 alternating checkerboard configuration that surprisingly reveals 52 arrows in total.

Variation: Here is a striking variation of the tile with four inward- and outward-pointing arrows. The inward arrows extend into continuous paths on a white background, creating the effect of interwoven arrowed ribbons.

Extra 3D Arrow Illusion

Let’s take a different direction from the experiments above and explore a 3D isometric illusion. This construction is inspired by classic impossible figures depicting ambiguous stacks of cubes, whose apparent number can change depending on how you interpret their spatial arrangement.

Start with a hexagonal boundary (Fig. 1) and overlay a triangular isometric grid (Fig. 2). Then draw six interlocking arrow shapes around a central point, folding their tails inward (Fig. 3).

Finally, use three colors to shade the isometric planes, or apply directional line hatching, to give the flat arrows a three-dimensional, interlocking appearance.

Curious about the mathematics behind these impossible 3D arrows? Math lovers can explore the geometry and construction 👉 here.

Deconstructing impossibility

Gianni Sarcone

A quick study of impossible interlocking cubes, taking the same paradoxical geometry from line drawing to watercolor and high-contrast digital collage.

The drawings use isometric projection to represent a three-dimensional cubic structure. The geometry appears consistent at first, but the planes intersect in ways that cannot exist in physical space. What functions as a back face seamlessly projects forward to become a front face, creating a continuous spatial contradiction.

The Geometry of Wonder

Gianni Sarcone
impossible objects: nested tribars

One of my finest sculptures: nested triangles, the central one in wood, the others in stainless steel…

nested tribars

Just kidding. It’s an impossible tribar composition — a sculpture that can exist only in the eye and the mind.

The Penrose triangle (or Penrose tribar) is generally credited to Roger Penrose, who, together with his father Lionel Penrose, published it in 1958 as an “impossible object.” However, the visual idea of creating paradoxical triangular forms and impossible geometries has older precedents.

Japanese visual culture is often mentioned in discussions of geometric illusion because Edo-period (1603–1868) art, decorative motifs, and craft traditions reveal a deep fascination with complex patterns, ambiguous spaces, and unconventional perspectives. Elements found in traditions such as sankaku mokkō (triangular motifs), karakusa patterns, architectural ornamentation, and woodworking designs show how Japanese artists and craftsmen explored visual structures that challenge perception. While no confirmed direct predecessor of the Penrose tribar has been identified in Japanese art, these examples belong to a broader historical tradition of creating forms that play with geometry and the limits of visual interpretation.

Japanese tribar

A glimpse below into traditional Japanese fabric patterns, where triangular designs reveal how interlaced geometry can create the sensation of impossible structures.

Kagome patterns

To round things off, it’s worth mentioning the Valknut, a Scandinavian symbol dating back to around the 7th century whose interlocking triangles closely resemble the tribar.

valknut

Triple Klein Bottle

Gianni Sarcone

Τριαλάβαστρον (Trialábastron), a triple Klein bottle, is an artistic exploration of Klein bottle geometry. In topology, the Klein bottle is a non-orientable surface that cannot be embedded in three-dimensional Euclidean space without self-intersection, though it can be smoothly realized in four dimensions.

A close relative is the Möbius strip, another non-orientable surface in three-dimensional space. On such surfaces, a continuous path can return to its origin with reversed orientation, revealing how geometry can twist the notion of inside and outside.

a triple Klein bottle

Here is another representation of a triple Klein bottle—UK sculptor Alan Bennett’s striking construction of three Klein bottles nested within one another. Of course, “inside” only applies in the sense of their embedding in physical space; from a topological standpoint, they remain entirely separate, non-interacting surfaces.

recursive Klein bottle

Your Brain vs. Geometry: Rooftop illusion

Gianni Sarcone

Believe it or not, the green and purple rooftops are congruent—identical in shape, size, and angles. What changes is not the geometry, but your perception of it. Perspective, orientation, and contextual cues lead your visual system to interpret the same form as two different structures.

rooftop illusion, related to shepard tables

This effect is closely related to Shepard’s tabletop illusion and earlier studies in which identical parallelograms (A and B), when rotated (and superimposed), are perceived as different shapes, as the brain prioritizes interpretation over measurement.

Since some still insist these roofs are not congruent, I’ve put together a short animation that shows otherwise.

animated rooftop illusion

The Borromean Tribar

Gianni Sarcone

This form belongs to the family of impossible figures, more specifically to the Penrose triangle, or tribar.

impossible figure

At first glance, it looks entirely manufacturable. The structure appears to be made from three identical square rings (Fig. 1), each pierced by a circular opening and arranged in three mutually perpendicular planes (Fig. 2). Together, they seem to interlock seamlessly, forming an impossible three-dimensional tribar that evokes a trefoil knot and its endless over-under weaving.

If this sculpture looks physically realizable to you, congratulations: your visual system has just accepted a geometric impossibility.

the making of the borromean tribar

Could such an object be built? Not exactly. One solution would be to twist one of the junctions slightly, but that trick would be immediately noticeable here because some of the angles would no longer appear perfectly square (90°), as shown in the picture below. Another possibility would be to leave a small gap at one junction and view the sculpture from a carefully chosen angle, allowing perspective to hide the discontinuity.

This is how a real 3D Borromean Tribar would appear…

How a Human Bone Inspired the Eiffel Tower

Gianni Sarcone

Few people know that the human femur—the body’s largest and strongest bone—played an indirect role in the thinking behind the design of the Eiffel Tower.

Part of the tower’s structural logic can be traced to Swiss engineer Maurice Koechlin, chief engineer in the firm of Gustave Eiffel. While determining how forces would travel through the iron frame, Koechlin applied a principle that places material along the natural paths of tension and compression.

A comparable pattern had been described earlier by Zurich anatomist Hermann von Meyer. His research revealed that the femur’s internal structure forms a network of delicate struts known as “trabeculae.” These tiny elements follow the directions of mechanical stress inside the bone, creating a highly efficient system of support—even though the femoral head sits off-center from the shaft.

The mathematician Karl Culmann later showed that these trabecular patterns correspond closely to the principal stress lines calculated in engineering. His method, called graphic statics, provided a visual way to map how forces move through structures.

This link between anatomy and engineering influenced nineteenth-century structural thinking. The same principle—placing material only where forces demand it—guided the development of lighter, more efficient frameworks in bridges, cranes, and reinforced-concrete designs.

Beyond Constructible Forms: The Undecidable Bars

Gianni Sarcone

In 1934, the Swedish artist Oscar Reutersvärd sketched a peculiar triangle made of small cubes, neatly aligned on an isometric grid. Everything looked geometrically sound—until the mind tried to assemble it in real space.

Soon after, Lionel Penrose and Roger Penrose published their famous Penrose Triangle—three beams joined by apparently right-angled joints—and M. C. Escher explored similar paradoxes in works such as Waterfall and Ascending and Descending.

This triangular paradox has distant echoes in ancient Greek geometry, but Reutersvärd gave it a clear visual form: the impossible figure.

That’s the charm of impossible figures: every part looks right, yet the whole quietly breaks reality.

I began exploring these paradoxical structures in the 1980s. My interest grew naturally from the meeting point of two inclinations: a mathematical curiosity about spatial logic and a visual fascination with form. Over time I produced many variations—sometimes rediscovering ideas that others had already touched upon, occasionally arriving at configurations that felt genuinely new. In geometry, complete novelty is rare; most discoveries emerge as unexpected turns within an existing landscape.

One example from that period is the study shown here, created in the late 1990s and titled Undecidable Bars.

© Gianni A. Sarcone, 1997-2001

Parallel bars appear to run calmly side by side, yet their connections quietly sabotage the logic of space. Perspective slips from one segment to another, forcing the eye to accept incompatible viewpoints at the same time.

Each element seems perfectly normal.
Together, they form a structure that cannot exist.

Some bars appear to pass through others; some join where no joint should be possible. The geometry behaves as if the object were bending through space, while every line still respects the conventions of perspective drawing.

The result is an undecidable figure—a form the eye can follow effortlessly, but the mind cannot reconstruct.

Available as fine art print from my online gallery.

Over the years I have created hundreds of images built on similar principles, across different formats and media. If these works interest you for a book, exhibition, or monograph, feel free to contact me.

Here’s a simple 18-frame animation of my Op Art piece—work in progress.