Driven random script

[steeleb]

Hi all. Im trying to use a script to control rotation:

Basically I want to build 1 object with a script that makes the rotation of XYZ a random number between the positive and negative range of another attribute in the scene...

ie: object.Xrotation = rand(attr,-attr);

so I can ramp up and down the jitter from a global control (attr)

BUT when I duplicate this object I want the new object to get its own random values and not have the exact same script attached.... what Im getting atm is all the duplicate objects jitter ramps up and down with the global control, but the random motion is all the same as it is all driven by the same script... please help..

Ben Steele

[failure]

In the "Duplicate options" window turn on the "Duplicate input graph" option

[steeleb]

Yeah, I tried that, but that duplicates the object that is setting my global attribute, so instead of having 1 global control I have as many as I have controlled objects. This opens the door to another question I had about duplicating.

If you have a heirarcy, say a polyObj parented to a locator parented to a locator. The top locator is for positioning/rotating the group, the second locator has the script (mentioned in my first post) on its rotations (for random jitter controlled by a global attribute) and the polyObj just is. How do you dulicate this group so the top locator is a copy, the second locators script still sees the global attribute input, but isn't simply a copy of the same script generating the same random movement; and the polyObj is an instance (so I can globally edit all instances at a later date from the master PolyObj? I am about to do it manually for between 500-1000 leaves... ie: duplicate the locator structure, reapply the script to the second locators rotations, instance the leaf and group it in; then place the whole shebang and start again. I think I may have to go this way anyway because I need to then duplicate the leaf again to make a rigid body of it so it can fall come autumn, whilst being free of the jitter.... if only the particle instancer detected the boundaries of its instances for collision purposes..

Ben Steele

[failure]

"but that duplicates the object that is setting my global attribute"

There is no such thing as "global attribute" in maya ( at least not in the version i'm working on ). Attributes are properties of nodes.
Proper way to do this is by using the global variable which holds the limit value for rand function. Global variable is not in any relation to any node/object so it don't get duplicated when you duplicate a node.

Just execute piece of script declaring and initialising the variable. Refer to this variable in your expression. That way you'll be able to create as many duplicates as you like without multiplying the control.

If you want to change the rand range just execute another piece of script changing the value of that global variable.

If you want to have a fancy slider refer to maya help to see how you can create custom ui elements and use them to drive variable values.

Concerning your hierarchy question:
Use global variable in second locator script (as explained previously ) and let the polyObj be instance already. So you have this starting hierarchy: parantLocator->expressionLocator->instancedPolyObj.
Now you just make ordinary duplicate of parent locator and you get: parent locator is a copy, expression locator is copy and uses global variable( which is visible everywhere ) and polyObj is just another instance ( because when you duplicate an instance maya just creates another instance of source node. There is no such thing as instance of instance )

[steeleb]

Thankyou so much for your reply.... you have filled in the gaps that were hurting my brain.
Would I need a slider to be able to animate the global value? the only problem I am getting NOW is with the instanced polyObj. It seems that it isn't an instance after duplicating the group, I've built the original group with an instanced polyObj, but when I duplicate the group and edit the original polyObj the changes are only reflected in the first instance... I tried it without duplicate options, with duplicate input connections and with duplicate input graph.......

[failure]

"It seems that it isn't an instance after duplicating the group"

My mistake. Select root locator and type "instance -leaf" in the command line. This will duplicate hierarchy and instance all of the leaf nodes.

"Would I need a slider to be able to animate the global value?"

No. Most elegant way I can think of is to use animation curve. It may be confusing if you've never done it so here we go step by step:
- in the command line type: createNode animCurveTU -name "animCur";
- open the outliner, make sure that "Display->DAG objects only" is turned off.
- select animCur in the outliner.
- open the graph editor and set some keys just to see the curve( you'll adjust the curve later )
- open the expression editor ( make sure that animCur node is still selected )
- create the expression: $globalRandomRange = animCur.output;
( $globalRandomRange is your variable used by rand )
- edit the animation curve in the graph editor.

[steeleb]

I had a go at controlling the $globalRandomRange by an attribute on a locator, and a script

$globalRandomRange = attribute;

that way I can select the locator and adjust or keyframe the intensity. I'll try the anim curve, thanks.

The 'instance -leaf' doesn't work for this, it duplicates the parentLocator as a duplicate (good), then the scriptLocator as an instance without the script (noGood), but the polys is an instance (good). I think I will just have to duplicate the two locators, instance the poly, parent it all up and then add the script to the script locator...

thanks so much for all your help failure.

Ben Steele

[failure]

"I had a go at controlling the $globalRandomRange by an atributte on a locator"

It's the same thing. Difference is that now you have animation curve attached to ( redundant ) object. If it's easier for you that way, it's ok.

"The 'instance -leaf' doesn't work for this"

Think you're right. Well then this must work - this script does exactly what you've said in above post:
( hierarchy is loc1->loc2->poly )

// unparent
parent -w loc1|loc2|poly;
parent -w loc1|loc2;

// put this in a loop for multiple copies
duplicate -n "loc1_copy" loc1;
duplicate -n "loc2_copy" loc2;
instance -n "poly_instance" poly;
parent poly_instance loc2_copy;
parent loc2_copy loc1_copy;
// end of loop

// reparent
parent poly loc2;
parent loc2 loc1;

[steeleb]

ok.... so how do you run a loop? could I specify the number of times ie: 500?

secondly... I wanted to add a second script (to the script locator) so that each duplicate would be a random scale (rand (0.5,1.5); I tried this..

if (frame==1)
{
seed(1)
loc2.scaleX = rand(0.5,1.5);
loc2.scaleY = loc2.scaleX;
loc2.scaleZ = loc2.scaleX;
}

but... the seeds need to be different in each copy.. is it possible to have a seed a random number and then give that a seed so it repeats on rewind? or is there an easier way....

[failure]

First, please note the difference between:

expressions - pieces of mel code attached to objects, driving atrributes and executed as animation plays ( every frame )

and

scripts - pieces of mel code executed by user. Commonly used to automate things you do thru ui; object creation and editing, animating, etc.

By looking at your posts I kinda got the feeling that you don't see a difference between two. Maybe I'm wrong.

So, what you posted above is exspression - the thing that drives the animation. What I posted before you is script - the thing you'll use to automate creation of 500 objects.
To see how scripts work try this: Open the script editor ( not expression editor ) and in the bottom field type:

global proc myCommand( int $n ){
int $i;
for( $i = 1; $i <= $n; ++$i ){
print $i;
print " ";
}
}

Now select all you typed and press ctrl+enter. This will execute the script. Since this script is definition of custom procedure you won't see any output. Now in the command line type:

myCommand( 10 );

and check out the output in the script editor upper window. Your custom procedure gets called just like any other mel command ( of course it does not do anything useful, just prints out some numbers )

Now paste following into script editor:

global proc duplicateMyStuff( int $numCopies, string $loc1Name, string $loc2Name, string $polyName ){

float $copyOffset = 2;

// unparent
eval( "parent -w " + $loc1Name + "|" +$loc2Name + "|" +$polyName );
eval( "parent -w " + $loc1Name + "|" +$loc2Name );

// loop
int $n;
for( $n = 1; $n<= $numCopies; ++$n ){
string $loc1NewName = "loc1_copy" + $n;
string $loc2NewName = "loc2_copy" + $n;
string $polyNewName = "poly_instance" + $n;
duplicate -n $loc1NewName $loc1Name;
duplicate -n $loc2NewName $loc2Name;
instance -n $polyNewName $polyName;
parent $polyNewName $loc2NewName;
parent $loc2NewName $loc1NewName;
// move result a bit
move -r ( $n * $copyOffset ) 0 0 $loc1NewName;
}
// end of loop

// reparent
parent $polyName $loc2Name;
parent $loc2Name $loc1Name;
}
// end of script

select it and press ctrl+enter.
Make sure that you have loc1->loc2->poly hiearachy in your scene and in command line type: duplicateMyStuff( 500, "loc1", "loc2", "poly" )

Tweak a script to suit your specific needs.

Regarding seed:
All random number generators are in fact pseudo-random. They start from some number called seed and generate random looking sequence. Same seed - same sequence.

By setting seed before calling each random you are acctually forcing it to generate exactly the same number over and over. Just delete the seed line and it should be ok.
If you want "same randomness" each time animation plays just create new locator or some other dummy object and attach expression:
if( frame == 1 ){
seed( 1 )
}

Now seed() gets executed only once for the whole scene at the start of animation

[steeleb]

sorry, I get the difference, I probably just substitute names either way or use other words like code etc. My sloppiness that there is no room for in coding, so absolute.

double thanks for the script, I added the -un flag to
"duplicate -n $loc2NewName $loc2Name;" so the expression controlling the rotations was included.
And now I have to include a scale line to give each new leaf a random scale rand(0.5,1.5) and I think I've almost worked it out...
BUT (ah the famous but) now, whenever I open my scene..
A: I have to declare the $wind value even though its declared in an expression. ($wind = wind.strength) and
B: I have to select each rotate expression and hit edit before it see's them, when I command line render the scene, no animation occurs??

ever experienced this?

[joojaa]

I would opt for a ddifferent strategy! Id make a dummy object taht contains the source for your stored values.. Copy the entire networks and then slect all the dummy values and dele the dummy objects freeing the values connections in the expressions thmseves and then loop an attach thenm to 1 controll node for further use.

[failure]

What is $wind used for, again?
Look, this could go on forever
Why don't you just post exactly what you want to achieve so we can suggest you optimal way(s) of doing it.

[steeleb]

yeah, its getting a bit like that.

What I am making is an origami tree for a stop motion animation. The leaves jitter every two frames depending on the wind. the leaves will be parented to small branches to scale up "growth" in spring and come fall they turn into rigid bodies and fall. I will bake the simulation on every second frame and step the tangents.

I have a polygon leaf "leafP" and two locators "leafL", and "leafR" grouped like this LeafL|leafR|leafP. "leafR" jitters based on this expression..

if (frame==0)
{
leafR.rotateX = 0;
leafR.rotateY = 0;
leafR.rotateZ = 0;
}
else if (frame%2==0)
{
leafR.rotateX = rand($wind,-$wind);
leafR.rotateY = rand($wind,-$wind);
leafR.rotateZ = rand($wind,-$wind);
}

(the "if (frame==0)" line is a 'zero' frame for running the "duplication" script)

The "leafL" locator is so I can place each leaf on the tree and rotate it to a pleasing angle whilst still allowing the "leafR" under it to jitter. The $wind value is the global that controls the intensity. Does that make sense?

Everything was working fine, but as I mentioned before, when I save the scene and re-open it, the scripts don't seem to do anything until I first specify a value for $wind, then the locator "wind" with the "strength" attribute and this expression: $wind = wind.strength ...takes over. Secondly I have to select each "random rotate" script and hit 'edit' before it does anything... nothing moves when I render, even if it moves when I playback.....?

[steeleb]

ooops

"Everything was working fine, but as I mentioned before, when I save the scene and re-open it, the scripts don't seem to do anything until I first specify a value for $wind, then the locator "wind" with the "strength" attribute and this expression: $wind = wind.strength ...takes over. Secondly I have to select each "random rotate" script and hit 'edit' before it does anything... nothing moves when I render, even if it moves when I playback.....? "

there I go using the wrong word again...

find/replace "scripts" with "expressions" in that last bit

sorry

[failure]

$wind is a global variable and must be declared as such in any script entity that is refering to it.

Otherwise the script/expression assume this is an undeclared local variable.

First line in both 'leafR' locator expression and 'wind' locator expression must be:

global float $wind;

Now they know they are refering to same global value. That automatically solves the second problem with batch render, and that is:
Variables do not exist until they are declared. You declared $wind thru ui and it exists in the ui session of maya. But when you batch render, the copy of scene is saved and if declaration is not in the scripts/expressions that are explicitely run during the playback the variable is not created and scripts that are using it will probably generate errors and be ignored ( see your batch log )

Same thing is causing the problem when you reopen the scene. If $wind is not declared the 'wind' expression cannot set it so it won't run. The 'leafR' expression also cannot run so leafs don't jitter.
When you set $wind value you implicitely declare it. Now it exists as a global variable. You must re-evaluate the expressions to recognize it ( by clicking edit in expression editor ).
Expression evaluator searches global namespace and finds out that $wind is a global variable and everything works peachy.

[joojaa]

the simplest way to initialize this is to open the script editor, select the select filter menu choose script nodes and make a new scriptnode with open/close evaluation (before), wich initializes the value.

[failure]

You'll still need to declare it inside each expression for everything to work properly.
Note the difference between declaration and initialisation.

[joojaa]

offcourse... BUt i still am pretty convinced that connecting to a node is a better way to go...

[joojaa]

offcourse... BUt i still am pretty convinced that connecting to a node is a better way to go...