Siggraph 2005 logo
Conference Exhibition Call For Participation Presenters Media Registration

emerging technologies

Khronos Projector

An interactive art installation that allows people to visualize movie content in an entirely new way. By actually touching and deforming the screen, the user can send portions of the image forward or backward in time.

Art and Science

When we view a still image or a motionless sculpture, we are free to direct our sight wherever we want over the entire work, perhaps only subliminally compelled by the compositional forces the author has instilled in it. This is barely possible when we view a movie, because we are forced to adopt a point of view both in space and time.

The Khronos Projector unlinks space and time in a pre-recorded movie sequence. It enables an infinite number of interactive visualizations. With the Khronos Projector, causality becomes relative to the spatial path we decide to follow on the image, which allows for multiple interpretations of the recorded facts. In this sense, the Khronos Projector can be seen as an exploratory interface that transforms a movie sequence into a spatio-temporal sculpture for people to explore at their own pace.

The Khronos Projector is a suggestive tribute to Einstein's Theory of Relativity: the temporal relationship between two physically separate events is a perception relative to the observer. It is not a serious platform for recreating any typical relativity paradox, because the interactive projection infringes one fundamental law of nature. Although it is true that temporal relationships are relative to the observer's inertial frame, causality is not relative (this follows from the fact that information cannot travel faster than light). Two events that are in causal relationship should therefore always maintain their temporal order. The Khronos Projector breaks this rule, but this is precisely what makes the experience interesting and fun.


From the artistic/cognitive point of view, the Khronos Projector suggests the possibility of freeing both filmmakers and audiences from the constraint of a pixel-ubiquitous time arrow. During a Khronos projection, we cannot change the nature of the pre-recorded events, only the perspective, only the way we perceive their temporal relationship. We are at the same time spectators of fixed movie content and, in a strong sense, directors of a personalized post-production process.

From the scientific point of view, the goal of this presentation is to gather as much feedback as possible from a large audience on a prototype "tangible" human-interface that tightly combines visual display and the sense of touch.


The Khronos program that runs the installation defines the spatio-temporal filtering surface through surface models (physical or non-physical) or by using real-time acquired data from a real deformable surface. Precise reconstructions of complex screen deformations are computed using a constrained, finite-difference equation method. The center of the pressure coincides with the (image) center of gravity of the darker "spots", and the amount of pressure can be inferred from the diameter of the spot. A proprietary "vision chip" performs this computation at up to a thousand images per second.


Presently, even filmmakers who are less devoted to linear narratives are forced to integrate the screen-ubiquitous time arrow as a fact in their work. But imagine a version of Hitchcock's "Rear Window" prepared for the Khronos Projector. The audience would be able to go backward or forward in time at the desired window, literally. The movie would contain several possible interleaved stories, depending on the way the space-time volume is explored.

The Khronos Projector also allows exploration of otherwise conventional movie content. This may interest people who may want to experience their own movies through the Khronos Projector.

Finally, the Khronos Projector, may represent an interesting human-computer interface for defining and visualizing arbitrarily shaped slices of volumetric data, (for example, scanned medical images). It could be a starting point for developing a pre-operatory interface capable of showing internal body sections mapped onto complex surfaces, displaying them just as they would appear to the surgeon during the actual operation. Surgeons could "see" inside a virtual body during pre-operatory work by "pushing" their hands against a deformable projection screen, instead of being limited to a set of (interactive) planar cuts, as they are now.


Alvaro Cassinelli
The University of Tokyo
alvaro (at)


Monica Bressaglia
Università degli Studi di Trieste

Ishikawa Masatoshi
The University of Tokyo