Karljoh an Lundin Palm e rius Norrk öping Vis ualization ...
Transcript of Karljoh an Lundin Palm e rius Norrk öping Vis ualization ...
Applications
CFD Sim ulation
Th e SH ARC aircraft is an
experim ental unm anned aerial
veh icle (UAV). In th is exam ple
th e air flow from a com putational
fluid dynam ics s im ulation (CFD)
is explored us ing m ulti-m odal
interaction. W h ile only
s im ple propertie s can be
rendered visually w ith out
cluttering th e display, th e
h aptic fe edback provide
continuous repre s entations
of th e data and ph ys ical guidance th rough out th e volum e .
H eart Blood-flow
M odern M RI-scanners are capable of
aq uiring anim ated blood-flow data
from w ith ing a beating h um an h eart.
Both th e poor tis sue contrast of th is
k ind of data and th e fact th at th e
nois ine s s of M RI data m ak e s
autom atic extraction of feature s
difficult, m ak e s it an intere sting target
for m ulti-m odal m eth ods . Th e h aptic
fe edback h elps th e radiologist
understand th e flow and guide s th e
exploration both ph ys ically and
m entally.
H aptic M ode
FAST AND H IGH PRECISION VOLUME H APTICS
Karljoh an Lundin Palm e rius
Norrk öping Vis ualiz ation and Inte raction Studio
Link öping Unive rs ity, Sw e de n
Proxy-based Volum e H aptics
Proxy-bas ed m eth ods for volum e h aptics us e a
proxy to internally repre s ent th e h aptic probe . Th e
h aptic be h aviour is controlled by m oving th e
proxy and th e force fe edback is calculated from a
virtual spring-dam per connecting th e proxy and
th e probe .
Prim itives Solver
Th e proxy pos ition th at repre s ents th e h aptic fe edback th rough th e virtual spring-dam per for each tim e fram e is found by balancing th e force fe edback from th e spring-
dam per against th e force from th e prim itive s . Th is is done by th e solvers .
H igh Precision Analyth ical Solver
We h ave de s igned an analytical m eth od for solving th e balancing e q uation
and so find th e pos ition of th e proxy. Th is solver m ak e s us e of th e com m on
s ituation w h e re h aptic prim itive s are in configurations th at produce s
orth ogonal constraints .
Th e analytical solver is bas ed on iterative m ovem ents th e proxy point in
accordance w ith th e h aptic prim itive s in turn. During th e s e iterations th e
proxy pos ition repre s ents th e force exerted by th e applied h aptic prim itive s ,
onto th e currently proce s s ed prim itive .
General Num erical Solver
If th e orth ogonality re q uirem ent for th e analytical solver is not fulfilled,
th e solver fails and th e system ne eds to fall back on a m ore general solver
th at is capable of h andling any com bination of h aptic prim itive s , even non-
orth ogonal configurations . Th is is im plem ented us ing a ste epe st de scent
m inim ization of th e balancing betw e en th e fe edback and th e force from th e
prim itive s .
Volum etric Data
Th e volum etric data at th e probed pos ition is extracted to
control th e param eters of th e h aptic prim itive s , th us
indirectly controlling th e h aptic fe edback .
H aptic Prim itives
Th e h aptic prim itive s configured from th e volum etric data propertie s define th e
local h aptic be h aviour w h ich th en reflects th e local data in th e volum e .
Depending on w h ich prim itive s h ave be en s elected as a repre s entation of th e
data, and depending on h ow th e ir param eters are controlled, th e re sulting
h aptic m ode produce s different h aptic be h aviour. Each prim itive h as an
individual strength , direction and pos ition.
Plane Constraint
Th e plane prim itive is a 1D constraint, us ed to
s im ulate surface s .
Line Constraint
Th e line prim itive is a 2D constraint, follow ing th e
"bead on a string" m etaph ore .
Point Constraint
Th e point prim itive is a 3D constraint, providing a
re s istance to m otion in any direction.
Directed Force
Th e directed force prim itive
generate s a force is th e
defined direction.
Procedure
1 Put proxy at probe pos ition — zero force fe edback
2 M ove proxy in re spons e to force prim itive s
3 M ove proxy in re spons e to plane prim itive s
4 M ove proxy in re spons e to line prim itive s
5 M ove proxy in re spons e to point prim itive s
Procedure
1 Put proxy at probe pos ition
2 Initialize step length
3 Estim ate re s idual force and m ove th e proxy th e step length in
th e direction of th e re s idual force
4 If th e propagation ch anged direction m ore th an 9 0 degre e s ,
low er step length
5 Repeat 3– 4 until re s idual or step length is low er th an th e
m ach ine eps ilon