ways to look at expressions – Time based / procedure-driven animation

Controllers / calculations for user extensions

Basic examples (review maya docs)

Ball.scaleY = Ball.scaleY + 0.1 incrementing a value

Ball.scaleY += 0.1 [ += -= *= /= ]

Ball.translateX += 0.1

Conditional "IF" statements for resetting

if ( frame == 1 ) tx = 0 ; "==" tests equivalence

"!=" tests "not equivalent"

Two predefined variables are

"time" and "frame"

time = frame / framerate

Ball.scaleY = time + 1 24fps 1 frame = 0.0417

Ball.scaleY = time/5 + 1 30fps 1 frame = 0.0333

float $tDisp = time;

print ($tDisp + “\n”);

Attributes controlling others

Ball.scaleY = ball.scaleX

Joint2.rz = joint1.rz joints_exp.mb

One xform related to another / and with offset

Cube.scaleY = ball.scaleY

Cube.scaleY = ball.scaleY * 2

Incrementing a user-defined variable

Fundamentals book examples

bounce

bounce with friction

The standard order of operations applies to scripts in Maya. For example, in the expression

3 + 5 * 9 PG 43 of MEL book

Even thought the addition takes place first in the sentence, the multiplication is performed first.
( ) [ ]

! ++ --

* / % ^

+ -

< <= > >=

== |=

&&

||

? ;

= += -= *= /=

Definition of variables

Defining PI as a variable float $pi = 3.14159265

Using PI to for rolling ball / wheel rolling_balls_exp.mb

float $radius = 1;

Using sin and other functions

bouncing ball

Sin() web page

(sin(value * frequencymultplier) * amplitude) +/- offset

Sin/cos – circling spiral_out.mb

Reverse order

Abs(sin/cos)

Rolling cube rolling_cube.mb

Max( ) - foot walking

L.ty = max(0,cos(time)); simple_feet_exp.mb

L.tz = sin(time);

R.ty = max(0,cos(time + 3.1416)

R.tz = sin(time + 3.1416)

Linstep() and smoothstep()

Random functions – web page

Rand() tail_wagging_rand.mb

Noise() tail_waggin_noise.mb

Shrand()

Random direction motioni

Modulus to change direction periodically random_travel.mb

Time offset from an object with anim curve

`getAttr –t (frame – 2) pCube1.ty` timeoffset_follow

Adding controls (custom attributes):

EYES example from book pg 49

Creating a custom attribute:

Using the connection editor to attach to another attribute

Results in a 1 to 1 correlation

Addressing the new attribute in an expression:

                                    Book example: Create "Ball.revolutions" as a float from 0 to 1

Create expression as " Ball.rotateY = ball.revolutions * 360 "

MEL command to create custom attributes:
The History window output reveals two MEL commands

AddAttr and settAttr

the "keyable" flag can be used with AddAttr

AddAttr –k 1

(Also can use –smx (soft max value) in addition to max)

Custom Attribute Examples –

Newtons cradle controls Newtons_cradle.mb

Walking_exp_ctrls.mb

Walking_travel_ctrls.mb

Hip_blender_ctrl,mb

Fundamentals_book examples:

Unicycle

Circling

Inward spiral

Magnets

Windblownflower

Bottlebobble

Bullies