4/19/2000deepak bandyopadhyay / comp239 / intouch1 interactive multiresolution modeling and 3d...

4/19/2000 Deepak Bandyopadhyay / COMP239 / inTouch 1

Interactive MultiresolutionModeling and 3D Painting with a Haptic

Interface

Arthur D. Gregory, Stephen A. Ehmann, Ming C. Lin

{gregory, ehmann, lin}@cs.unc.edu

Brought to you by : <[email protected]>


Abstract

1) Intuitive 3D interface

2) Interactive multiresolution edit of polygonal mesh

3) “Directly” painting on surface

4) Haptic feedback

result create interesting and complex 3D objects !

Rooster created with inTouch


Motivation

• What’s in it for us soon-to-be VR experts ?• We need models!

humans

objects

places


Motivation

• What’s in it for us soon-to-be VR experts ?

© 1996 Brian Heston

• Virtual painting • the next killer app ?

• Maybe not, but I still think its cool!

• We need models!


Motivation

• What’s in it for us soon-to-be VR experts ?• We need models!• Virtual painting

• the next killer app ? • Maybe not, but I still

think its cool!

• Haptics•state of the art technologies

•Phantom•H-collide


3D painting• How it all began…

– Pat Hanrahan and Paul Haeberli, ‘Direct WYSIWYG Painting and Texturing on 3D Shapes’ (SIGGRAPH 1990) [HH90]

• [HH90] allows painting in object space, but…•Model must be divided into micro-polygons

•Change colors and material per vertex

•Painting is done in 2D parameter space


3D painting a la inTouch• Use texture maps instead of

per-vertex colors

• Use a 3D “brush function” instead of 2D

• inTouch allows direct painting onto object space…


3D painting a la inTouch• For each triangle within the brush radius…

– Compute the edge equations in texture space

– Use them to define a plane equation in object space

– Incrementally find 3D position of each texel while rasterizing

– Apply brush function at this position and modify the texel

• direct painting into texture map…

(u,v)(x,y,z)

triangle in object space triangle in texture space


Multiresolution Mesh Editing

• Multi-level model representation related by Loop subdivision rules

• Mesh editing by dragging with force feedback at any of the levels

• Two deformation styles - slide and stick


Haptics hardware

• Sensable Technologies PHANTOMs– 3 or 6 DOF force feedback device

http://www.sensable.com/products/phantom.htm

http://www.sensable.com/products/phantom.htm


Interfacing with PHANTOM

• GHOST toolkit

• H-Collide library– collision detection between a haptic

probe and environment

– need 1000Hz updates!

– Hierarchical scene representation

– Uses frame-to-frame coherence


Haptic Display

• Mesh modification– Triangle, movement vector, magnitude from H-Collide

– Compute new position of triangle and use subdivision rules to update finer mesh levels

– Pass new mesh to H-collide and compute coarser mesh levels by averaging

force


Haptic Display

• Painting– H-collide establishes point of contact of probe with

model and computes the force

– Probe becomes brush with specified color, radius and fall-off

– Push harder increase brush radius, deposit more paint


User Interface• 2D menu at edge of 3D scene• Use PHANTOM stylus as mouse

Pear by Gentaro Hirota


Prototype system

• IR2 as graphics server

• PC as haptics server

• VRPN for communication

• Display on PIT or monitor (not 3D)


Conclusions

• User comments:– Easy to modify globally or

in detail at a point

– Intuitive way of “sculpting” a 3D model

– Good haptic feedback

– Intuitive way of painting the model directly

Fox, by Sarah Hoff

(starting model = white icosahedron)


Results

•“Garl” - Observe the deformation

•Young Silvia the butterfly, 80k triangles

•Sylvia painted with inTouch

Models and painting by Arthur Gregory


Future Work– Two handed, multi-user, …

– More interesting brush functions…

– More interesting force feedback...

– 6 DOF...

– Paint in “real” 3D space (my project)

Potentially moving real object

Moving paintbrush

4/19/2000deepak bandyopadhyay / comp239 / intouch1 interactive multiresolution modeling and 3d...

Documents