Animcurve Integral

[ptb]

Is there a faster way to calculate the integral of an animcurve over a certain time than approximating it by adding up the keyframe values at each frame in a loop (which is executed by scriptjob)?

I want to control the speed of an object (meters/frame). But I don't want to play every frame (more than 2000) to see the resulting position.

[joojaa]

QUOTE(Ptb @ 09/30/08, 02:02 PM) [snapback]292567[/snapback]
(which is executed by scriptjob)?

Why n earth a scriptjob. (i mean a scriptjobb is the last tool id use for this) Dont use mel. (also NEVER step time ist slow just step the node)

Write a node. the anim curve is a picecevise smooth polynomial so yes you could actually do a elemantary solve of it quite fast. Tough i tested doing a anim a curve wich has a 10000 frames worth of data with random frames at keyframe every 5 frames stepping torugh all frames for pos takes a lot less tiem then you think if you do it right:

CODE
//suppose this scene;
file -f -new;
sphere -p 0 0 0 -ax 0 1 0 -ssw 0 -esw 360 -r 1 -d 3 -ut 0 -tol 0.01 -s 8 -nsp 4 -ch 1;
for ($i=0;$i<2000;$i++){
    setKeyframe  -time ($i*5) -value(rand(0,2)) "nurbsSphere1.ty";
}

CODE
createNode time;
connectAttr -f time2.outTime nurbsSphere1_translateY.input;

prepration.

CODE
//you need these line to calc
$thisSum=0;
for ($i=0;$i<10000;$i++){
    setAttr time2.outTime $i;
    $thisSum+=`getAttr nurbsSphere1\_translateY.output`;
}
print $thisSum;

takes less than a second on my secondary computer thats 3 years old.

this way its pretty fast (this is faster than stepping torugh global time), buy you can do it even faster by using a expression node but its considerably harder to maintain, also you can cache the bits your not calculating.

Also baking the result is slightly faster/as fast too as long as you run your own time to bake and d NOT update screen.

CODE
//preparation slightly different
createNode time;
connectAttr -f time2.outTime nurbsSphere1_translateY.input;

expression -s "global float $thisSum=0;\r\n$thisSum+=.I[0];.O[0]=$thisSum"  -o time2 -ae 0 -uc all;
connectAttr -f nurbsSphere1_translateY.output expression1.input[0];
addAttr -ln "out" -at double  |nurbsSphere1;
setAttr -e -keyable true |nurbsSphere1.out;
connectAttr -f expression1.output[0] nurbsSphere1.out;

//you need these line to calc

$thisSum=0;
bakeResults -simulation false -t "1:10000" -sampleBy 1  -sparseAnimCurveBake true -at "out" nurbsSphere1;
print ("Total Time: "+$totalTime+"\n");

this may get faster if you do not use the global var. and isntead use a nother conection slot.

Anyway a c++ node would be on order 10-50 times faster so youd be seeing. Anyway expecting some 1/10 of second to brutefrce the issue with mel in slightly unoptimal maya execution. Certainly if you store say 5-10 sections of values in array you only need to update one part of the array and now you are in 1/100 second wich is acceptable by most terms?

PS: this does not change the fact that animating like this si not entirely intuitive.

[ptb]

Thanks, Joojaa, this was helpful.

I didn't want to cycle through time, I was thinking about using something like this:

CODE
$thisSum=0;
for ($i=0;$i<10000;$i++){
    $thisSum+=`getAttr -t $i nurbsSphere1\_translateY.output`;
}
print $thisSum;

It seems to be about the same speed - which is ok. But still not very interactive (for scrubbing the timeline for example).

Ok, Scriptjob is a bit stupid. Expression is better. The update should be automatic with timechange, thats the point.

QUOTE
PS: this does not change the fact that animating like this si not entirely intuitive.

This is the purpose: I have an animated horse (staying in one spot)*. For certain reasons we're letting the environment move and not the horse. So the speed of the passing envorinment has to match the movement of the horse (which is accelerating and slowing down at some points). Do you see a more intuitive way to control the environment?

*unfortunatly the animators didn't move the horse forward, so transferring the animationcurve isn't possible, it has to be guessed.

[joojaa]

CODE
$thisSum=0;
for ($i=0;$i<10000;$i++){
    $thisSum+=`getAttr -t $i nurbsSphere1\_translateY.output`;
}
print $thisSum;

is 3 to five times slower!

[ptb]

QUOTE(Joojaa @ 09/30/08, 05:57 AM) [snapback]292586[/snapback]
is 3 to five times slower!

Oh, ok - then I'll use the second time node (didn't check with timerX or similar, first thought it shouldnt make any difference). thanks

[joojaa]

QUOTE(Ptb @ 09/30/08, 05:14 PM) [snapback]292589[/snapback]
first thought it shouldnt make any difference

So did the autodesk support.