HHlathe

Lathe combines a force image of a simple cylindrical stock with

a holographic video image of the same geometry. An interacting

person can see, feel, and carve the multi-modal simulation

into an arbitrary rotationally-symmetric shape. The final shape

can be dispatched to a 3D printer to generate hardcopy.

- overview

- touch

- poke

wendy plesniak &

ravikanth pappu

Lathe has three subsystems: the haptics

module, the holovideo module, and the

model manager. The haptics module runs

our force simulation and drives the force-

feedback device. The holovideo module

precomputes holograms, and drives rapid

local updates on the holovideo display.

The model manager keeps the visual and

haptic representations in sync.

The force simulation runs at an average

servo rate of 5kHz, and the holovideo

update rate is 10fps. The system operates

with 1s of lag between haptic and hologram

updates. Thus, typically, as a person lathes,

the surface is immediately felt to change

and seen to change a second later.

Lathe achieves near-real-time holovideo updates by

using a set of precomputed holograms of cylindrical

stocks having different radii. The final image is

then assembled from appropriate regions of this

precomputed hologram set, and only changed in

regions where the model has been affected by a

person's carving. By making line-level changes, we

avoid recomputing the entire 36MB holographic

fringe pattern at each update.

Using such specific precomputed elements permits

only a limited set of images to be assembled. Our

third holo-haptic experiment, Poke, addresses

this problem by using more generalized precomputed

fringes to assemble a more arbitrary final image.

The force model is given by a 1D

NURB curve which sweeps out

a surface of revolution. Pressing

into the model with the Phantom

stylus causes a force to be displayed

back to the hand; pressing with

enough force causes model control

points to be displaced inward and

the stock deforms uniformly

around its circumference.

Finally, the completed model data

can be dispatched to a 3D printer to

produce a physical hardcopy of the

carved design. The model shown to

the right was printed on a Stratasys

3D printer. The entire process serves

as one example of a future design

and prototyping pipeline.

Selected references :

Ravikanth Pappu and Wendy Plesniak, "Haptic interaction with holographic video images", Proceedings

of the IS&T/SPIE's Symposium on Electronic Imaging, Practical Holography XII, January 1998.

Wendy Plesniak and Ravikanth Pappu, "Coincident display using haptics and holographic video",

Proceedings of ACM SGICHI Conference on Human Factors in Computing Systems, April 1998.

Wendy Plesniak and Ravikanth Pappu, "Spatial interaction with haptic holograms", Proceedings of

the IEEE International Conference on Multimedia Computing and Systems (ICMCS'99), June 1999.

Wendy Plesniak and Ravikanth Pappu, "Tangible, dynamic holographic images", in Kuo, C.J. (Ed.),

3-D Holographic Imaging. Wiley-Interscience (invited, in press).

Sponsors of this work include Honda R&D Company,

NEC, IBM, the Digital Life Consortium at the MIT

Media Laboratory, the Office of Naval Research

(Grant N0014-96-11200), Interval Research Corporation,

and Mitsubishi Electric Research Laboratories.