Constraints: Pose Sliders Question... Percentage versus ON/ OFF?

#1

Hello everyone,

I have a a few questions about Constraint Switching in a character.

I am rigging a character who needs to have several differents constraint set-ups.

Why might one chose to set up constraints with a Pose Percentage Slider versus a Pose On/ Off switch and vice versa?

(For example: Switching from FK Arms to IK Arms and back. Which pose storage method might be the best to use? )

If I need to switch the constraints of a character in the middle of a shot, would the switch be apparent to the audience in the character’s perfomance by a sudden pop in its limbs?

I am unsure with how to proceed with my set ups for this particular character at the moment so I would greatly appreciate any input that you may have to offer.

Thanks.

#2

Hello.

I would recommend that you use a percentage pose slider for FK-IK switching.
You might want to examine The Setup Machine’s rig, which has a very nice IK-FK switching pose.
http://www.anzovin.com/setupmachine/setupmachineam.html
Sample rigs are available for download, on the sidebar.

ON-OFF poses are better for things like fan-bone constraint poses – stuff which you just want to turn on and forget about.

Sincerely,

Carl Raillard

#3

Thanks Carl for your reply.

I looked at those Anzovin demo rigs and that leads me to the following situation:

When I take a pre-exsiting rig for practice and switch from FK Arms to IK Arms in an Action Window, the arms don’t remain where I positioned them (Once I switch between FK Arms and IK Arms using the pose sliders). The models actually start to get a bit mangled.

What I mean is that the arms jump to new positions and the keyframes that I set look differnt now as far as the arms are concerned.

I know that I am making some serious mistakes but I don’t know what they are.

What am I overlooking with this type of set up when I am animating?

Here is a practical example of what I am trying to accomplish:

Suppose I have a model of a basketball player.

I want to animate the basketball player to LEAP from the foul line and do a SLAM DUNK all in one shot.

From the point where the basketball player LEAPS into the air to just before he JAMS on the rim, I want the model’s arms to be FK Arms.

When the player GRABS (slams) the rim and HANGS for a moment or two I want to switch the model’s arms to be IK Arms (using pose sliders) as his body SWINGS around while his hands firmly grasp the rim.

Once the player lets go of the rim to land, I want to switch the model back to FK Arms.

(In my case I have been practicing using the Washer model from David Rogers’ book A:M 2002 A Complete Guide and one of the Anzovin demo rigs from the Anzovin web site)

If anyone can help or point me in the right direction I would really appreciate it.

Thanks

#4

Hello, again.

I’m not an expert, so maybe I shouldn’t be the one giving advice, but that has never stopped me before. :slight_smile:
Let me tell you how I do constraint switching. I’ll use your basketball player, as an example. Advance to the frame where the player JAMS, and create a keyframe for his body on this frame. In particular, the hips, torso, shoulders, upper arms, lower arms, and hands should have rotational keys. The hips and torso may also need translation keys (this varies with different rigs). Okay. Now select the IK target for the hand, and move and rotate it a little. Next, apply a Translate To and an Orient Like constraint onto the IK target. Dab the eyedroppers on the hand bone, the normal FK hand bone. This will move the IK target into its correct position. With the IK target still selected, toggle on the Key Translations, Key Rotations, & Key Bone buttons on the Frame Toolbar, and create a key. What this does is “bake” the IK target’s position and orientation. Now you won’t need the two constraints on it anymore. Delete these constraints; you’ll notice how the IK target remains in place. On the Pose Slider Panel, grind up the appropriate FK-IK pose, so that it is 100% IK. Finally, go back one frame and grind this same pose down to 0%.

As you can see, this method could just as easily be served with an ON-OFF pose for the FK-IK switch. But I still contend that such poses are better implemented with percentage sliders. I will explain.

The above method is labor-intensive, but it’s accurate. I’m a real fusspot about accuracy. Hopefully, though, I will become a better animator, and I will cease to rely on the above method. In the future I want to be able to switch from FK to IK on the fly, just by posing the IK target directly, and segueing between one and the other over the span of several frames. For instance, in your basketball example, I’d create a key for the character at the JAM frame, and another key five frame previously, and I’ll switch the pose from FK to IK over the course of those five frames. Someday!

A final note: When creating a FK-IK percentage pose which slides smoothly, you have to make sure the Kinematic and Orient Like constraint’s enforcement channels are set to “linear.” By default constraints are set to “hold” and that creates an abrupt jump. So you have to fiddle with constraint settings, to make them pose-sliderable.

'Hope this helps.

Sincerely,

Carl Raillard

#5

Carl,

Thank you so much for that reply!

I really appreciate you spending the time on your replies that you have (Believe me, I don’t mind at all that you are not an expert).

I had to read the details of your reply several times because these rig/ constraint setups are all new territory for me.

I understand what I am reading when I read it (ie: tutorials and your posts) but some of these things I need to actually “do” it to get a hands-on experience to truly know how to make it work.

As far as your method being labor intensive… I do not mind that at all as long as it works.

I have yet to develop a method yet so I can’t get the job done until I can.

I am going to try your method out and I’ll let you know how I have progressed in a while. I’ll have your instructions in front of me so that I can give it a shot and zero in on what areas I should work on the most.

Again Carl, thank alot!

Take care.

#6

Hey Carl, Thanks for that - you are a godsend!

I just started a little short and I wanted to use a really simple rig. I didn’t want to build any IK switching into it but I was worrying that I would have to for some parts of the animation. I just tried your method and it worked wonders!

#7

Hey, guys! I’m glad I could help! :thumbsup:

Here’s a tip Pequod gave me the other day: Constraint-switching is labor intensive. Instead of doing it on the first pass of your animation, try holding off until the second or third pass. For example, in Mechy’s basketball player example, you should animate the player jumping up and dunking the ball with FK throughout, and just try to ignore the drifting hands after he jams the ball. Work hard to get the timing of the piece right. AFTER the character looks like he is jumping up, hanging, and dropping back down in a believable way, THEN go back and anchor his hands on the hoop.

Timing always requires shoving keyframes around, and to have the IK-FK switch to worry about is a needless hassle. Try holding off until you are happy with the sequence in every other respect. Treat the constraint switch as a “beauty pass”.

Pequod also mentioned that after he does this, he usually wants to go back and fiddle with the timing some more! :smiley:

Ah, well. I still think it’s a good tip. It’s not good to be too fussy, at first. I’m preaching to myself, now.

Sincerely,

Carl Raillard

#8

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