mue 발표자료 박동규조미리나
TRANSCRIPT
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An Interactive Fire Animation on a Mobile Environment
DongGyu Park, SangHyuk Woo, MiRiNa JoDept. of Information and Communications Engineering, Changwon National UniversityDoHoon LeeResearch Institute of Computer Information and Communication, Pusan National University
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Motivation and Contribution• Fluid simulation
– Physics based on realistic animations of water, smoke, explosions, and related phenomena
• Advances in the mobile handset– The development of mobile hardware has accelerated.– The mobile handset which can process 4 million polygons.– Expected that the fluid simulation will be possible.
• Physics based models in Mobile Game– As PC games are converted to mobile, we expect that
physically based modeling will be implemented in mobile environment.
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Introduction-Mobile hardware• Display
– Small screen– 48x84 1bit pixel ->
320x240, 256 pixel(WIPI minimum requirement)
• Mobile Chipset– ARM 9 family : 200 Mhz– ARM 10 family : 400 ~ 600
Mhz– ARM 11 family : 400Mhz ~
1Ghz processor for Smart phone
• Small Memory size
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Introduction-Mobile 3D API• OpenGL-ES
– Low-level Graphic API– Widely adopted stan-
dard for Mobile device– Most OS’s, thousands of
applications– A foundation for high
level APIs• OpenInventor, Java3D,
game engines.
• JSR-184– Java Standardization
Request(JSR)– Mobile 3D Graphics API
for J2ME
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WIPI & NF3D• WIPI(Wireless Internet Platform for Interop-
erability)– Standard wireless platform in Korea
• About NF3D– Mobile 3D API based on OpenGL-ES– Support 3D camera, object handling functions
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Fire simulation on Mobile Games
• Mobile Game – “Rupee Story”– 3D adventure games– Interactive fire simulation on realtime game– WIPI + NF3D API
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Navier-Stokes Equation• NS Equation describes the flow of fluid. • The sum of inflow and outflow is 0. (Conservation of mass)• Conservation of momentum
– u : velocity vector field– t : time step– : fluid density– p : fluid pressure– v : coefficient of viscosity – f : external force
fu1
u)u(u
0u
2
p
t
fu1
u)u(u
0u
2
p
t Advec-tion Pres-
sure
Dif-fuse
External force
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Stable Fluid Solver• Stable Navier-Stokes Solver
– Analysis of evaluating solution is difficult.• Evaluate approximation Solution using numerical method
– Finite difference : Having instability that don’t conver-gence quickly.
• When the time interval is large, it is unstable.• the fluid velocity, we must use a small time interval
– Stable Fluid• Semi-Lagrangian : the method of getting velocity by back
tracking to the particle of current cell• Can tolerate the use of larger-than-desired time intervals
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Fire simulation• Fire consists of the components: Fuel, Oxy-
gen, Heat, Inert gas– Fuel + Oxygen Heat + Waste– If there is insufficient oxygen and fuel , the fire makes
smoke.• Physical phenomena around the fire
– As temperature rises, the surrounding air(smoke) has ris-ing force
– As the air moves away from the source of fire, the tem-perature goes fall down
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Fire simulation• Fire and smoke can be simulated by using
buoyancy force and cooling factor – Buoyancy force
• This can raise high temperature of gaseous.– Cooling factor
• As fire and smoke go away from the energy source, the temperature goes down.
• The temperate goes fall down by certain ratio and is conducted to neighbor cells
• We can draw the color of fire and smoke based on its temperature.
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Interaction• Use the external force term in NS equation.• When the game character approaches to the
fire, external force affect the velocity field. • Interaction for various effects.
– Perturbing the flame and scattering smoke.
Apply external forces for interaction
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Coloring the Fire and Smoke• The temperature(wavelength) of the fire de-
termines the color of the flame.• As the temperature increases; the color
changes from red, green (yellow), blue and white– EX) As the temperature changes, the color of the flame is
not same on burning tree.
850 ℃
1100 ℃
1500 ℃
Low temperature
High temperature
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Coloring the Fire and Smoke• The temperature of the fire determines the
color of the flame.• Set the standard temperature
– Separate fire and smoke by specific temperature• Define the temperature value of grid cell for
simulation– Float value between 0 and 1– To use RGB color system for coloring flame and smoke– Set five basic colors: linear interpolation of assigned col-
orsLinear interpolationLinear interpolation
Low temperature
High temperature
< The color of the flame >
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Billboard• Orienting the polygon based on the view di-
rection– Two dimensional animated texture maps– As the view changes, the orientation of the polygon change– Using to show complex geometry model as one image
• EX) tree, cloud– Alpha texturing + Fire animation explosion and smoke ef-
fect
Simulated billboard on Mobile 3DSimulated billboard on PC
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Billboard• Using fixed point operation of NF3D • Using off-screen buffer
– Save simulation result to off-screen buffer– Copy it as image– Texturing on billboard– White background process alpha blending transparently
128
12
8
Off-screen buffer
Image
Billboard
128
12
8
Off-screen buffer
Image
Billboard
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Billboard• Using alpha blending
– Control transparency of Billboard– Specified color is complete clearness
(a) does not apply alpha blending
(b) apply al-pha blending (50%)
(b) erased original white background and apply al-pha blending
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Implementation• The simulation are applied on our mobile 3D
game “Rupee Story”• Real-time Interaction with Game Characters,
demo
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Performances• NF3D supports Frame per second check func-
tion• Tested on emulator and FPS(Frame Per Sec-
ond) check functionSimulation and rendering results
0
5
10
15
20
25
30
32*32 48*48 64*64 96*96 128*128
Simulation grid
FP
S
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Performances• The change of billboard refreshment period
– According to importance of game and fluid simulation• The change of simulation grid size
– Simulation speed is depend on the size of the grid– For realtime game application we should have to find ap-
propriate grid size– By an experiment, 64*64 grid size is good for our realtime
game application
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Conclusions and Future Works• Physically based model for animating and render-
ing fire and smoke with using billboard technique on a mobile environment.
• We demonstrated that this model could be used to produce realistic looking fire and smoke animation and plausible realtime interaction for mobile games.
• More realistic fluid effect on new mobile 3D plat-forms
• Implement water and ocean effects on mobile plat-forms
• Implement with level-set methods that are very ef-fective methods for tracking fluid surfaces.
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Thank you