Computer Animation CPSC 453 Fall 2018 Sonny Chan Animation is the - PowerPoint PPT Presentation

Computer Animation CPSC 453 – Fall 2018 Sonny Chan

Animation is the act, process, or result of imparting life, interest, spirit, motion, or activity. –Michael Ashikhmin (Chapter 16)

Principles Keyframes Procedural Outline for Today Physics-based Characters Motion capture

Principles of Animation Luxo Jr. – Pixar Animation

“There is no particular mystery in animation… it’s really very simple, and like anything that is simple, it is about the hardest thing in the world to do.” –Bill Tytla, Walt Disney Studio, 1937

The Illusion of Life Cento Lodigiani

“The thing I wanted to do in Luxo Jr. was make the characters and story the most important thing, not the fact that it was done with computer graphics.” –John Lasseter, Pixar Animation, 2013

Luxo Jr., Pixar Animation Studios, 1986

Twelve principles: which ones did you notice? • arcs • squash and stretch • secondary action • timing • straight-ahead and pose- • anticipation to-pose action • follow through and • exaggeration overlapping action • solid drawing skill • slow-in and slow-out • appeal • staging

Keyframe Animation

Key Frames

What properties can we animate using key frames?

Position Angle / Orientation Shape / Deformation Keyed Properties Colour / Material Brightness / Light Visibility

Animation is all about timing!

1.25 1 0.75 Cubic Ease Function 0.5 u ( t ) = t 2 (3 − 2 t ) t ∈ [0 , 1] 0.25 0 0.25 0.5 0.75 1 -0.25

[from easings.net]

Keyframe Interpolation • Each animation parameter is keyed at various times • Ease functions are used to interpolate between values

Procedural Animation

For the special cases when a mathematical function outputs precisely the desired motion, given some animator guidance.

Planetary Orbits θ ( t ) = ω t x ( t ) = r cos ( θ ( t )) y ( t ) = r sin ( θ ( t ))

Perlin Fractal Noise • Define a grid over the domain (1D, 2D, or 3D) • Generate a random vector at each grid point • Compute dot products at interior points, interpolate • Scale and add on to original function to produce fractal noise

Procedural Clouds DigitalRune Engine (XNA)

Sine Waves n X z = A i sin ( f i r i t ) i ( x − x i ) 2 + ( y − y i ) 2 p r i =

Ocean Waves Unreal Engine 4, Ben Allen

Physics-Based Animation

Rigid Bodies Deformable Objects Fluids [images from Ron Fedkiw, Stanford University]

Newton’s second law of motion: F = ma

Physics Simulation • Physical quantities are related/defined by a = 1 differential equations F = m a m F a = d • Apply forces to objects, Z dt v v = a dt solve for displacements v = d • If we know the force on an Z dt r r = v dt object, and its mass, how might we find its position at a given time?

Numerical Integration • Forces are often unknown a priori no closed form solution - we can apply a discrete time simulation - • Use numerical integration to solve differential equations e.g. first order taylor expansion: - Z v ( t ) = a ( t ) dt v ( t i +1 ) = v ( t i ) + ∆ t a ( t i ) ⇒

Mass Particles Cinema 4D

Multi-Physics NVIDIA PhysX Flex

Character Animation

James F. Blinn Nested Transformations & Blobby Man, 1987

: DEF WORLD Table 1. Meanings of Blobby Man variables FOV, ZN, ZF PERS Extension. A dancers term EXTEN TRAN XSCR, YSCR, ZSCR forward and for bending BACK, 1 ROT backwards (x axis) ROT SPIN, 3 Rotation. A dancers term for ROT 1 ROT TILT, rotating the body and shoul- -XLOOK, -YLOOK, -ZLOOK TRAN ders left and right about the 1, -1 SCAL 1, vertical (z axis) SCENE DRAW Angle of body leaning left BTWIS and right (y axis) The variables XLOOK, YLOOK, and ZLOOK determine Head nod NOD the "look-at" point. BACK, SPIN, and TILT tumble the Head shake NECK scene about this point. Then XSCR, YSCR, and ZSCR direction that the Angular LHIP,RHIP position the look-at point on the screen. XSCR and leg is kicked YSCR might very well be zero, but ZSCR needs to be Angular distance that the leg LOUT,ROUT some positive distance to move the scene away from the is kicked eye. The assembly SCENE contains the contents of the Angle the leg is twisted about LTWIS,RTWIS scene, and can be designed independently of how it is its length being viewed. Our cube scene again: Knee bend LKNEE,RKNEE Ankle bend LANKL,RANKL DEF SCENE Arm rotation to side LSID,RSID GPLANE DRAW Arm rotation forward and LSHOU,RSHOU - CUBE, TRAN,X1,Y1,Zl, ROT ,ANG,3 DRAW back DEg CUBE, SCAL,.3,.4,.5, TRAN,-5,-3.8,Z1 DRAW UatR3 e TPAN' DW SCAL O 'O Arm rotation about its own LATWIS,RATWIS oir, W T"-K,: H6 10 DHJ fSCAL, 0 length KEm A : I , -Q0: Elbow angle LELBO,RELBO Blobby Man A few years ago I made a short animation of a human $CAL, figure called "Blobby Man" to illustrate a new surface HTR R ERE 76 DEF TORSO modeling technique. Leaving aside issues of modeling, LEFTLEG, TRAI,-O.178,,00, DRAW RGRTLEG, TRA,O. 178O0O0, DRAW the figure itself is an interesting example of nested SPHERE, TRAN.0,0,O.08, SCAL,0.276,0.162,0.153. DRAW HP EH transformations. I have, in fact, used it as a homework DRAW , ROT,EXTEX.1, ROT,BTWIS,2, ROT,ROT.3. BODY assignment for my computer graphics class. (Gee, I DEF BODY guess I can't do that any more.) SPHERE, TRAX,0,0,0.62, SCAL,O.306.0.21,0.6, DRAW Here is Blobby Man. His origin is in his stomach, and SHOULDER, TRAN.O.O.I. ROT,EXTE1,1, ROT,BTWIS,2, ROT,ROT.3, DRAW he stands with the z axis vertical. The only primitive DEF SHOULDER element is a unit radius SPHERE centered at the ori- DRAW SPHERE SCAL,O.45,0.153,0.12, , TRAI.0,0,0.153, ROT.IOD.1, gin. The parameterized variables are all rotation DRAW HEAD ROT,NECK.3. LEFTARN , TRAN,-O.46.O.O, ROT,LSID,2, ROT.LSHOU,1, ROT,LATWIS.3, DRAW angles. Their usage is defined in Table 1. RGHTARI , TRAN, 0.46,0,0, ROT,RSID,2, ROT,RSHOU.1, ROT,RATWIS,3, DRAW The WORLD is the standard one given above. SCENE DEF LEFTLEG DEF RGHTLEG looks like PUSH PUSH LHIP, 3, 3, ROT ROT RHIP. ROUT. LOUT, 2, 2, ROT ROT DEF SCENE -RHIP, 3, -LHIP, 3, ROT ROT GPLANE DRAW LTWIS, 3, ROT RTWIS, 3, ROT RAXe0 C , THIGH DRAW THIGH DRAW SCAL,O 10,1 , TRAN,XM,YM,ZM, ROT ,RZM,3, Figure 5. Blobby Man wang: DRAW TORSO 0, -0.86, TRAH 0, 0, 0, -0 .86, TRAN LKHEE, RNEE, I, 1, ROT ROT , DRAW CALF DRAW CALF 0, -0.84, 0, 0, -0.84, TRAN 0, TRAN 3 Bo RANKL, LANEL. I 1 ROT ROT The actual articulated parts are in Figure 2. Some DRAW DRAW FOOT FOOT Bobv MLI rhhere are several tricks POP POP ii primitive body parts are defined as translated and hat are especially i:otablei squashed spheres in Figure 3. A picture of the result DEF RGHTARN DEF LEFTARN appears in Figure 4. The viewing parameters are PUSH PUSH UPARN DRAW DRAW UPARM unulato ilamatwor ve t 0, -0.55, 0, TRAN 0, TRAN 0, -0.55, LELBO, 1, ROT RELBO, 1. ran4tor ROT t:a ZN=5. 17 It is nlot necessary to POP ZF=10.7 LOWARN DRAW DRAW LOWARK iRt is used tb DI TRAN 0, -0.5, 0, 0, -0.6, YSCR=-1.6 ZSCR=7.9 TRAN 0, XSCR=-. 1 1 }RAW I . : AometNhOl.S, -08$etime --* r<2, ALX A. Lt HAND DRAW HAND DRAW 3b rAhsiitio:ns rand1 rotationsIiCbr ac.tumulate tn Iti BACK=-90 SPIN=-30 TILT=O POP POP 816bby Mai-i's leBg 60il:d ha )ked I Foi exKamrple,,: YLOOK=O ZLOOK=O XLOOK=O I YN=O Figure 2. Body of Blobby Man. ZM=1.75 XM=O [from J. Blinn, IEEE Computer Graphics & Applications , 1987] LLEG DEF October 1987 63 DRAW TAL ROT I NL ETC TR100, , 0:84 DRAW CAL Mc: :: :t4 rG: TRA 00: :DEF C:LY -- - DRAW CALF ::::i t -,-. t. LANL I DRAW FOOT with:,f n:e N4 ;l torig a thIere are trLinsforuled Obec ½ ts I 71 Mie of the nesting can bo dspe a 3t one, , BILyM F' iving ... : DEF LLEG PUSH THIG DRAW Ies arii zero. picture ofI thi th(ler a4ng tda All I0. as, TRAN 0. O# ie 5 Th:e viex-wr ig the saiie but t1- ing I LKNEE1 ROT I I gles aSre aii DRAW CALF IECK28 O: 0o NOD:26: TRAN o"s ROUt 3 ::3 LHRIP=Ow RKN:: 1KXL, I1 ROT L UT R TWI:9 0o rFOT LKNEE DRAW I I=4o5 LSN U=; LATWIS -90 ) a LU0 90 POP FAT4Is=l 1RS0 t4O AS =112 BOS: 2 R:L hics & Applcatiom rputer G /a