Query attribute value...??

[_stev_]

I'm not completely sure what you want here. Are you trying to create an expression with a script? Or are you just wanting to know how to create the expression.

To make the expressions with MEL use the "expression" command.

[_stev_]

Can you create a custom attribute that stores this inital value? Then query that custom attr.

[futurcraft]

Hi Stev,
Well I want to call an already created expression (with the -ae flag set to zero initially) in the middle of my script to execute it when one of my rig controls is translated... and I am also having trouble in jus accessing a simple translateX value of my control shape into my "for loop" condition.. I get an error saying invalid use of Maya object.
here is the code..

expression -s "L_A_FootCtrl_1.translateX= 10;" -o L_A_FootCtrl_1 -n "stretchExp" -ae 0 -uc all ;
for (L_A_FootCtrl_1.scaleX> 10)
{
stretchExp;
}

any solution..??
Thanks,
Nikhil.

[futurcraft]

goin by this script, what i wanna do is.. that when I scale the control beyond a particular value.. I want to then translate it in space... so I need to query the scale attribute... and then change the translate attribute of the same control with the expression

[_stev_]

I don't think you can use the control attribute like that in a for statement. Try using the getAttr command to assign it to a variable, then use the variable.


float $ctrlScale = `getAttr L_A_FootCtrl_1.sx`;

[futurcraft]

I modified the expression and changed the for loop into an if condition.. but before me even changing my custom stretch attribute, the expression is executed...
do I have to set the node state of the expression to zero and then enable it within the condition?? and after the execution of the expression maybe again reset the node state back to zero again??

expression -s "L_A_FootCtrl_1.translateX= 10;" -o L_A_FootCtrl_1 -n "stretchExp" -ae 0 -uc all ;
float $ctrlScale = `getAttr L_A_StretchyFootCtrl_1.stretch`;
if ($ctrlScale > 5)
{
stretchExp;
}

[_stev_]

Maybe you don't need an expression here. You could just manipulate it with the script.

[futurcraft]

well.. this is jus a sample test expression.. my actual expression is what I am using for the stretchy control of my rig.. where I have an expression driving the scale attributes of my joints based on the output values of the distance between node..
so I actually require an expression to drive the scale.... basically the purpose being... calling an expression to be executed within a script.. I dont want my expression to be executed by default.. but only when called to be executed by the script when a condition is satisfied......

right now.. the expression is gettin executed by default...
is there any way I can control this...??

[_stev_]

You could put the condition statement in the expression.

[futurcraft]

Hey Stev..!!
thanks for the trick...! It worked... n by the way.... I saw ur reel... I must say tht u've done an awesome job in rigging those characters... did u use a rigid bind for the dynamic truck in ur reel...?? I mean.. the truck kinda deforms as it crashes... so I presume u used dynamic joint chains to react to the wall which was a rigid body...?

thanks...
tc...

[_stev_]

Glad you got it working.

Thanks for the nice words about my reel.

The truck's dynamics where all done with rigid bodies. A set for the shocks and for the hood. The mesh of the truck for the hood was bound to joints. And the joints were driven by the rigid bodies for the hood.

Lata,
Stev

[futurcraft]

Hey Stev..!!
thts a really good way of doin it..! I really loved the way u combined real world physics in tht simulation.. thanks anywayz..
tc,
Nikhil.

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