Animation symmetry?

[krispo]

HI all,

im character animating for games, and wanted to know if its possible to make a 'mirror image' of an animation.

for example, if i animate a character side rolling to the left from a standing position, i could 'flip' it so that the character rolls to the right.

this isnt simply a reverse in time, (i can flip the animation in timescale, making it 'play backwards' - but the animation is still in reverse).

this would be SO useful for gaming animation, i thought something might be out there for this.

Im not using the 'clip editor mixer' thing (as it appears to suck), just a null heirarchy.

I hope that made sense anyway...

Many thanks,
john.

] John Hedley
] Graphic Artist, Unique Development Studios AB, Sweden
] john@uds.se
] john@afilmcalleddads.com

[stevesayer]

Try scaling the keys vertically in the graph editor, making sure the pivot is at 0 value. You may need to be very precise about it, but you can always tweak afterwards.

[krispo]

I had tried this, but its so difficult, and only works for around 15% of keys...

still playing..

thanks,
john.

[joojaa]

Yes you could use trax, but this would mean you would have to design your sekeleton/ whatever so that the info can inteligently be mirrored... and also you would need two distinct sub characters to acomplish this.

One other way would be to create a script that does the same thing... a bit tedious at first but handy in the future (this is the method i would opt for in your case, trax would be better offcourse)

[spamkill]

I'd recommend a script. I ended up writing one for our artists to use after having to edit several hundred animations for the last game I worked on. It make a placeholder set of joints (with IK handles, etc) to hold the information, then it copies the motion channels from the left side of the body onto the placeholders. After that it copies the motion channels from the right side of the body to the left side, and from the placeholders to the right. Then it flips the appropriate channels so that everything moves in the proper direction. It took a bit of time to make, but now we can just hit a button to swap which leg starts a walk, or which arm dribbles a ball.
If anyone's interested I can post some example code.

[stevesayer]

In reply to:
I'd recommend a script. I ended up writing one for our artists to use after having to edit several hundred animations for the last game I worked on. It make a placeholder set of joints (with IK handles, etc) to hold the information, then it copies the motion channels from the left side of the body onto the placeholders. After that it copies the motion channels from the right side of the body to the left side, and from the placeholders to the right. Then it flips the appropriate channels so that everything moves in the proper direction. It took a bit of time to make, but now we can just hit a button to swap which leg starts a walk, or which arm dribbles a ball.
If anyone's interested I can post some example code.

Please post the code! This script would be so useful for us when we use skeletons with baked motion that need reversing/mirroring. If you'd rather mail it, my address is
ben@televirtual.com

[spamkill]

Here's an example, you can use the same principles found below for arms with fingers, legs, feet, etc. It takes a lot of scripting and troubleshooting, but once you're done it makes some tedious animation tasks really effortless. If you get stuck on a command, look in the MEL Command Reference in the MAYA HTML docs.

//Swap Arm Motion Example
/*
This is just enough script to give you an idea of how to make a script to swap the motion from side of a body to another.

Before you try the script you must do this:
Make two arms with these joint names shoulderL shoulderR elbowL elbowR wristL wristR
Now add IK handles to them named armL and armR
You can parent a box to each wrist to see the wrist rotations better

Key both arms doing something (animate IK handles and wrist rotations) then run the script.
The motion should swap between the two.

I cut a bunch of stuff out, so it may not work, pretty easy to troubleshoot though.

-Spamkill

*/

//Create Temp Arm
select -cl;

joint -n XSHOULDER -p 0.660417 0 0.619575 ;
joint -n XELBOW-p 1.498507 0 0.566723 ;
joint -e -oj xyz;

joint -n XWRIST -p 2.049683 0 0.604474 ;
joint -e -oj xyz;

//Add IK handle
select -r XSHOULDER.rotatePivot ;
select -add XWRIST.rotatePivot ;
ikHandle -n XIKHANDLE;

//deselect everything
select -cl;

// -------- LEFT to TEMP ---------
//Copy IK handle motion from left arm to temp arm

copyKey -time ":" -float ":" -hierarchy none -controlPoints 0 -shape 1 {"armL"};
pasteKey -option replaceCompletely -copies 1 -connect 0 -timeOffset 0 -floatOffset 0 -valueOffset 0 {"XIKHANDLE"};

//Delete left arm IK handle keys
cutKey -time ":" -float ":" -hierarchy none -controlPoints 0 -shape 1 {"armL"};

//Copy motion from right arm to left arm

copyKey -time ":" -float ":" -hierarchy none -controlPoints 0 -shape 1 {"armR"};
pasteKey -option replaceCompletely -copies 1 -connect 0 -timeOffset 0 -floatOffset 0 -valueOffset 0 {"armL"};

//Delete right arm keys
cutKey -time ":" -float ":" -hierarchy none -controlPoints 0 -shape 1 {"armR"};

//Copy IK handle motion from temp arm to right arm

copyKey -time ":" -float ":" -hierarchy none -controlPoints 0 -shape 1 {"XIKHANDLE"};
pasteKey -option replaceCompletely -copies 1 -connect 0 -timeOffset 0 -floatOffset 0 -valueOffset 0 {"armR"};

//copy left wrist keys and paste to temp wrist

copyKey -time ":" -float ":" -hierarchy none -controlPoints 0 -shape 1 {"wristL"};
pasteKey -option replaceCompletely -copies 1 -connect 0 -timeOffset 0 -floatOffset 0 -valueOffset 0 {"XWRIST"};

//Delete left elbow, wrist keys
cutKey -time ":" -float ":" -hierarchy none -controlPoints 0 -shape 1 {"elbowL", "wristL",};

// ---------RIGHT to LEFT ------------

//copy keys from right wrist to left wrist

copyKey -time ":" -float ":" -hierarchy none -controlPoints 0 -shape 1 {"wristR"};
pasteKey -option replaceCompletely -copies 1 -connect 0 -timeOffset 0 -floatOffset 0 -valueOffset 0 {"wristL"};

//Delete right elbow, wrist
cutKey -time ":" -float ":" -hierarchy none -controlPoints 0 -shape 1 {"elbowR", "wristR"};

// ----------- TEMP to RIGHT ----------
//copy temp elbow keys and paste to right elbow

copyKey -time ":" -float ":" -hierarchy none -controlPoints 0 -shape 1 {"XELBOW.tx"};
pasteKey -option replaceCompletely -copies 1 -connect 0 -timeOffset 0 -floatOffset 0 -valueOffset 0 {"elbowR.tx"};

//copy temp wrist keys and paste to right wrist

copyKey -time ":" -float ":" -hierarchy none -controlPoints 0 -shape 1 {"XWRIST"};
pasteKey -option replaceCompletely -copies 1 -connect 0 -timeOffset 0 -floatOffset 0 -valueOffset 0 {"wristR"};

//--- Flip Curves ---

//flip only the curves that need it!

//arm translations
scaleKey -scaleSpecifiedKeys 1 -time ":" -float ":" -timeScale 1 -timePivot 0 -floatScale 0 -floatPivot 0 -valueScale -1 -valuePivot 0 -hierarchy none -controlPoints 0 -shape 1 {"armL.translateX", "armR.translateX"};
//arm rotations
scaleKey -scaleSpecifiedKeys 1 -time ":" -float ":" -timeScale 1 -timePivot 0 -floatScale 0 -floatPivot 0 -valueScale -1 -valuePivot 0 -hierarchy none -controlPoints 0 -shape 1 {"wristL.ry", "wristL.rz", "wristR.ry", "wristR.rz"};

//Delete temp arm
delete XSHOULDER;

//end