Pretrigger Video Tutorial For Quick Muscle Sim

[anthonymcgrath]

hi guys
can anyone tell me what the scripting is that this chap writes out in his muscle sim video tutorial
muscle sim video

the compression is really low and I cant quite read it. I've copy n pasted what I CAN see below:

int $preTrigger = leg01_jnt.preTrigger;
knee_JNT.rotateZ = 'getAttr -t (frame) + $preTrigger + (leg02_jnt.rotateZ);

please help - this is perfect for what I want to do
cheers
ant

[ptb]

Nice tut you found there,

change

knee_JNT.rotateZ = 'getAttr -t (frame) + $preTrigger +(leg02_jnt.rotateZ);

to

knee_JNT.rotateZ = [/b]getAttr -t (frame + $preTrigger) leg02\_jnt.rotateZ[b];

• deleted the last +;
• changed ' to ` (wrong symbol) and added one at the end

[joojaa]

QUOTE(Ptb @ 06/28/07, 04:43 PM) [snapback]268824[/snapback]
knee_JNT.rotateZ = [/b]getAttr -t (frame + $preTrigger) leg02\_jnt.rotateZ[b];

Well thats not necessarily a very smart piece of advice for several reasons. It works but its not necessarily smart form a effect point of view.

see what happens when maya evaluates is it builds a graph and iterates it trough in reverse order to obtain the result, now that connection does not graph, thus maya cannot place it in the right evaluation context, further maya needs to reference the connection by name. This makes maya run slower then it needs, so it has following problems:

• Its not interactive (but thenagin neither are the dynamics)
• It relies on naming, so when you reference /rename it you get into heaps of porblems
• Its defeats the dg, purposefully and evaluates it 2-3 times more leading down to a speed penalty that can be exponential if theres many of these in the scene.

other than that its fine (theres a better way tough). Just so you know, it will come and bite you one of these days.

The tutorial isn't the best one ive seen about muscles. I saw a better one few years back.

[anthonymcgrath]

ptb:
thanks alot I owe you one

joojaa:

well you lost me with some of that there joojaa hahaha - can you point me to the muscle tutorial at all that you saw in the past?

can you suggest an alternative way of tackling this effect? Basically I have a robot character with simple muscle systems in the arms - I just want them to start moving (ie: simple scale of a cluster in X) prior to the animation or joint rotation which I will be doing with FK or IK.

[joojaa]

I dont store all tutorials i see

like i said this ones fine if you only have a few of them and never intend to reference rhe thing. However whan you do you have 3 options:

2 inside maya ones and 1 api one:

the inside options are as follows:

use a frame cache node, is a bit unoptimal for later use but its sure as hell is the fastest one.

duplicate the anim curve, ok thes is a management nightmare unless you do a mel hook to update the other curve with a scriptjob on change. But this is by far better come evaluation time.

the api solution is more optimal tough:

make a node thet loops back on itself to querry the anim curve values at separate poin in time.

Now all of theese are more of a hastle to the user unless automated properly, wich isnt that hard but not probably for the avereage artist.

[anthonymcgrath]

err... joojaa what in the name of moses did you just say? It sounded like SWAT talk prior to storming a terrorist swamped building or something hehehe!

well as it turns out that script worked a treat. I've done a quick playblast of the muscles and they can be seen to flex prior to the elbow joint rotation. You can check it out on my wip page here (near the bottom of the page)....

my wip

this method is fine for what I want the character to do and to be honest its probably a bit of overkill really as it aint too noticeable. I also got to simplify the method the chap talks about in the video as my muscles aren't connected to clusters or owt - they're just various pieces of mesh being deformed by non linear deformers

cool thing is I can hook this same script up to numerous attributes such as hydraulics and fluid motion down a bit of rubber pipe so it'll appear to have movement in the various components prior to the elbow or other part of the body moving

[ptb]

Concerning the good ol' "what Joojaa's talking about"-topic:

here i once posted an example for the use of the framecache node:
http://www.highend3d.com/boards/index.php?showtopic=237717

Since it's probably not efficient in combination with this expression it's perhaps not what he's talking about concerning the usage, but you could get the idea how to connect it.

And the dublication of the anim curve is no good idea because you loose the keyframe control for the time offset which is very valuable.

BUT... I also think that for rather modest setups in a none-prof. environment evaluation isn't that big of an issue (when it works it works, full stop).

[joojaa]

Well its fine to say something works, but if its works in direct contradiction to how maya gets it performance its not very sane. You can do this, but its like not brushing your teeth, you will quite likely pay for not understanding it one day. ill post again to explain this later.

i agree this is insanely complex way to do the same thing, but its doing the dg a local favor at expense of memory. The node is very very much much better. Anywya now im doing it the way dg wants things done. its important since DG IS MAYA!

QUOTE(Ptb @ 06/29/07, 07:23 PM) [snapback]268916[/snapback]
And the dublication of the anim curve is no good idea because you loose the keyframe control for the time offset which is very valuable.

Not necessarily, what you do is when you duplicate your node in the scriptjob (monitor the keyframe list), you insert a custom time into it and this custom time itself is derived form your current time fed by plu minus average node. Now thsi si setup heavy way so i dont use it, but its smarter in many ways because it plays ball with the dg in rather nice way.

here let me exemplify this VERY quickly (this si definitely not production ready but exemplifies the idea):
CODE
global proc refreshCrv(string $str){
copyKey -time ":" -float ":" -hierarchy none -controlPoints 0 -shape 1 ("nurbsSphere1."+$str);
pasteKey -option replaceCompletely -copies 1 -connect 1 -timeOffset 0 -floatOffset 0 -valueOffset 0 ("nurbsSphere2."+$str);
}
{
file -f -new;
sphere -p 0 0 0 -ax 0 1 0 -ssw 0 -esw 360 -r 1 -d 3;
sphere -p 0 0 0 -ax 0 1 0 -ssw 0 -esw 360 -r 1 -d 3;
refresh;
currentTime 1;
setKeyframe -breakdown 0 -hierarchy none -controlPoints 0 -shape 0 {"nurbsSphere1"};
currentTime 24;
move -r 0 0 10 nurbsSphere1;
setKeyframe -breakdown 0 -hierarchy none -controlPoints 0 -shape 0 {"nurbsSphere1"};
createNode -n Tz animCurveTL;
connectAttr -f Tz.output nurbsSphere2.tz;
createNode -n Tx animCurveTL;
connectAttr -f Tx.output nurbsSphere2.tx;
createNode -n Ty animCurveTL;
connectAttr -f Ty.output nurbsSphere2.ty;
createNode plusMinusAverage;
connectAttr -f plusMinusAverage1.output1D Tx.input;
connectAttr -f plusMinusAverage1.output1D Ty.input;
connectAttr -f plusMinusAverage1.output1D Tz.input;
//this will control offset its nonkeyable because you
//dont want to automatkcally key thsi but you can still individualy key it
addAttr -ln "offsetTime" -at double  |nurbsSphere1;
setAttr -cb true |nurbsSphere1.offsetTime;
connectAttr -f time1.outTime plusMinusAverage1.input1D[0];
connectAttr -f nurbsSphere1.offsetTime plusMinusAverage1.input1D[1];
refreshCrv("tx");
refreshCrv("ty");
refreshCrv("tz");
setAttr "nurbsSphere1.offsetTime" -4;
}
//okay nothing fancy thi will drop out of the effect but wait

//this will hook chanages in curve editor
scriptJob -ac nurbsSphere1_translateZ.a "refreshCrv(\"tz\")";
scriptJob -ac nurbsSphere1_translateX.a "refreshCrv(\"tx\")";
scriptJob -ac nurbsSphere1_translateY.a "refreshCrv(\"ty\")";

now important: i intetionaly left out acting on set key its not hard to add but i got to go... you get the picture. just that i have other things to do and the following luines get a bit trciky (Its not that its 3 lines in fact but i need to insert it quite deep into mayas factory scripts). To get the picture edit the curve in the curve editor and it the child will update on release (you can make it update on drag but thats a api job).

PS you must see the difference in gui actions and nongui actions.

PPS. it is possible to use the api functions to get out the onioning data directly wich makes this faster bt the loop node is better general utility