Transcript presentation

Interactive Mesh Sculpting
Using a Haptic Device
Goal
A method to continuously sculpt or
deform a planar mesh using haptic
interaction is implemented. Moreover, this
mesh has an image of the final model
mapped on.
Approach
Image mapped on a planar mesh
 Phantom Omni Basic Haptic Device
 NURBS surface is used
 Different tools to improve sculpting

Force Feedback Foundation
It allows the user to interact with it by
applying and receiving forces.
 Interacts with graphics applications
 Can make objects feel sticky, soft,
rough, viscous

Previous Work
Haptic Device
Avoiding interpenetration between
virtual objects
 Allowing the user to paint in virtual
environments
 Teleoperation of objects
 Touching textures

Mesh Sculpting

Free Form Deformation
 Control
points define the vertices of a
parallelepiped
 Using control points can be cumbersome

Subdivision solids
 Each
subdivided solid has damping, mass
and stiffness

Virtual clay
Characteristics of the Project
Haptic Device
Movement in 3 dimensions
 Mouse is constrained to 2 dimensions
 Limited range of motion
 Force rendering

NURBS
Provide advantages over other surfaces
 Using OpenGL implementation
 Automatic texture mapping
 Knot array affects continuity of the
surface

Particle System
Defined as a set of particles that
evolves over time
 Control points in NURBS are the
particles
 Particles have attributes like position,
velocity and force

Runge-Kutta4
Method used to solve differencial
equations
dx
v
dt
(1)
dv f

dt m
( 2)
Implementation
HLAPI and OpenGL
High level haptic rendering
 Provides rendering/collision detection
and useful data structures
 hlBeginFrame and hlEndFrame

Data Structures

Vertex class
 Has

attributes like position and velocity
ParticleSystem
 Contains

list of control points
NURBS
 Draws
the mesh
Features/Tools
Sculpting
 Forces are rendered when we touch the
surface.
 Sculpting includes both pushing and
pulling the surface.
 We are using the stylus button to
switch between push and pull modes.
Brush

Induces force on more than one control
point at a time
This is the point
of contact
The green points
are also affected
3D Paint
Painting in the 3D model is reflected on
the 2D texture
Show/Hide Particles
Showing particles
Closer look
at the
image
Hiding particles
Rotations
It allows us to look the image from
different angles
3D Cursor
It simulates the shape of a pen
Force Feedback
This
is the default mode, but can be
disabled.
If disabled, no forces are rendered,
but the mesh can still be sculpted.
Results of this comparison are shown
in the Results section.
Basic Algorithm
1.
2.
3.
Initialize the application
Create the mesh and texture map it with
the image
Sculpt the mesh using the haptic device:
a.
b.
c.
4.
5.
Rotate the mesh
Select a brush or single point sculpting
Apply forces to the mesh
The new position for the control point is
calculated and the mesh is drawn again.
Repeat step 3 until sculpting is done.
Major Issues
Sense
of depth is difficult to
implement
NURBS sampling parameters needs to
be adjusted
Haptic device kicked occasionally
while rotating the surface
Results
Comparing the Haptic Device
and the Mouse
Mouse
No force feedback
Points moved one at a
time, but can move
continuously if
implemented
User touches the
control points
Picking control points
may be difficult
Haptic device
Force feedback exists
Points are moved
continuously
User touches the mesh
since the haptic device
provides this configuration
No need to pick control
points
Mapping Haptic Device to
Graphics Simulation
NURBS in OpenGL
An
efficient way to draw NURBS
Provide different parameters to
control the surface
The mesh is 12x12 control points
Hardware acceleration in the graphics
card should be disabled
Interactive Sculpting
Initial image
Final image
Lips Deformation
Initial image
Sculpting the lower lip
Side view of the image
Common error in the sculpting
process
Side view of the final mesh
Front view of the mesh
Comparing Force Feedback
and No Force Feedback
Haptic device as a 3D mouse
 Identifying if we are touching the
surface

Haptic feedback
No haptic feedback
Lips
4 minutes
2.5 minutes
Nose
1.6 minutes
2 minutes
Water bottle
6 minutes
6 minutes
Finger
3 minutes
3 minutes
Door handle
3.5 minutes
3 minutes
Mouse
2 minutes
2 minutes
Mountain
3 minutes
2 minutes
Cream bottle
4 minutes
4 minutes
Example
This curve in the lips can be clearly
created in the first image but does
not exist in the second image.
The height of the lips does
not seem natural in the
second image.
This line between the lips
clearly separates them but
it is not the case for the
second image.
Results
Aesthetic
quality of the image and 3D
model are better when using haptic
interaction
Some curves in the mesh are not
steady
Same results can be achieved without
force feedback but time will increase.
Conclusion
Conclusion
Haptic
interaction provides an easier to
use and faster way to sculpt a mesh.
We implemented a few of the many
tools that will enhance the sculpting
process.
Practice is needed to perceive the
cursor’s Z location.
Conclusion
Real time interaction is important
 NURBS provided flexibility and
important properties
 Sense of touch can provide new forms
of interaction

Future Work
Future Work
New
editing tools
 E.g.
a selection tool
Adding
 NURBS
NURBS
 How
knots on the fly
parameters should be adjusted
limitations
to model hands, bottles?
Future Work

Different views of the mesh
 Each

view has a different angle
Integration with image editing software
 Attract

users attention
Image recognition
 Identify
boundaries and apply rules to the
control points near the boundary

3D Paint