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Acck ! - Foot Sliding !!!
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Acck ! - Foot Sliding !!! // Tech Forum
Post by Humdinger // Aug 6, 2008, 5:01am
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Humdinger
Total Posts: 319
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I am encountering that greatest of all evils…foot sliding.
I have seen this both with my own rigs and using the 'tank girl with handles' object from the Library.
Using Tank Girl with handles record a keyframe at 0…then scrub to frame 30 and record an identical frame there.
Now scrub to frame 15 …grab the IK handle at the waist and drag down. The rig bends at the knees and the feet stay planted to the ground as they should.
But if you play back the animation the right foot slides inwards while the left foot stays planted.
I have looked into the details of the handles and locks and what not and can not see any settings that differ that would cause one 'foot' to stay planted while the other moves/ slides inward.
As with Recording Morphing I am assuming there is something I am missing here.
Note: I made no adjustments to tank girl with handles library object… just grabbed her right from the library. |
Post by tomasb // Aug 6, 2008, 5:39am
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tomasb
Total Posts: 261
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try to change position interpolation for IK handles in FCurve editor. Default is bezier interpolation which is not good for feet. |
Post by Humdinger // Aug 6, 2008, 5:58am
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Humdinger
Total Posts: 319
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Hi Tomasb...
thank you for the quick reply.
Assuming I am doing what you asked correctly I still have the right foot sliding.
When posing the character/rig in the real-time view the right foot never moves, it only moves once I play back the animated sequence.
Note that as before the left foot stays planted as it should.
Tried other things /checkboxes for the handle at the waist, although the changes did produce 'results'..the darn foot still slides, admittedly not very much, but I am hoping to get it to behave as the left foot is.
Once again this can not be seen in the real time view while posing, only during the playback of the animation.
From my untrained eye the settings on the feet / locks and IK handles appear identical on both 'feet'. |
Post by Humdinger // Aug 6, 2008, 6:09am
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Humdinger
Total Posts: 319
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Well..
I did something that made it work as I expected, just not sure what.
:D
I will try things again later today and make notes of my changes. |
Post by Humdinger // Aug 6, 2008, 6:14am
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Humdinger
Total Posts: 319
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Hmmmm
Quick check...more testing later.
So if I select the IK handle at the waist the Interpolation is set to FK.
If I change that to IK both feet stay put.
Does that make sense ? |
Post by Humdinger // Aug 6, 2008, 2:00pm
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Humdinger
Total Posts: 319
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I must have mis understood the manual when reading about the 'Pose Only' checkbox for the IK Handles.
Unchecking that box on both Foot IK Handles has got both feet sticking to the ground.
:jumpy: |
Post by jamesmc // Aug 6, 2008, 2:25pm
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jamesmc
Total Posts: 2566
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Foot sliding occurs in 2D and 3D.
The most common explanation is that the feet are in sync with the forward motion of the walking figure.
Meaning that the feet will slide forward because the figure is moving forward.
It's handled a little differently in 2D, but in 3D it's handle by forcing the feet to be firmly planted on the ground. To do this, one can:
(1) Adjust the time the foot is on the ground (using interpolated curves)
(2) Use an object as a guide for foot placement (scaled steps) and ensure the foot doesn't go past that, the later making the object invisible. Null objects are better, but trueSpace doesn't have null objects.
(3) Do a follow through on the feet with the body going up or down depending on the part of the walk cycle - this forces the feet to be on the ground for a longer period and ties the feet to an upward or down motion, rather than a forward motion.
If you one thinks about it, feet are used as the anchor points for a real life walk cycle. For every action there is a reaction. i.e. when a foot pushes off the ground, the body goes up and forward. When a foot hits the ground, the body goes down and forward.
The key here is to relate the feet to the up and down movement of the body, rather than the forward motion of the body.
That way, the feet don't lock in with the forward momentum, but with the upwards and downwards momentum. |
Post by transient // Aug 6, 2008, 4:30pm
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transient
Total Posts: 977
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This is good advice, but I think you'll find humdinger already knows this stuff. He posted a very nice run cycle a while back, if my memory is kosher.
I beleive clintonman has made a constraints system for workspace, including null objects, although I'm not sure they will work in 7.6. I haven't really had the time to do much animation lately, maybe it's time to have a closer look at 7.6's bone tools. |
Post by Jack Edwards // Aug 7, 2008, 2:01am
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Jack Edwards
Total Posts: 4062
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Watch your curves in the FCurve editor. The default is bezier. Which will cause things to float around.
If you want something to move and then stop abruptly and/or hold position, then you need to change the interpolation between the "stopped" keyframes to Linear.
You can also use a Custom Bezier to create abrupt changes in direction. CTRL-clicking on the bezier handle with allow you to split the handles. |
Post by Humdinger // Aug 7, 2008, 3:16am
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Humdinger
Total Posts: 319
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This is good advice, but I think you'll find humdinger already knows this stuff. He posted a very nice run cycle a while back, if my memory is kosher.
Hmmmmm if it was using TS 7.0+ that may have actually been an import of BVH from Poser 5 after using the Walk Designer.
Foot sliding occurs in 2D and 3D.
The most common explanation is that the feet are in sync with the forward motion of the walking figure.
Meaning that the feet will slide forward because the figure is moving forward.
It's handled a little differently in 2D, but in 3D it's handle by forcing the feet to be firmly planted on the ground. To do this, one can:
(1) Adjust the time the foot is on the ground (using interpolated curves)
(2) Use an object as a guide for foot placement (scaled steps) and ensure the foot doesn't go past that, the later making the object invisible. Null objects are better, but trueSpace doesn't have null objects.
(3) Do a follow through on the feet with the body going up or down depending on the part of the walk cycle - this forces the feet to be on the ground for a longer period and ties the feet to an upward or down motion, rather than a forward motion.
If you one thinks about it, feet are used as the anchor points for a real life walk cycle. For every action there is a reaction. i.e. when a foot pushes off the ground, the body goes up and forward. When a foot hits the ground, the body goes down and forward.
The key here is to relate the feet to the up and down movement of the body, rather than the forward motion of the body.
That way, the feet don't lock in with the forward momentum, but with the upwards and downwards momentum.
What !?!? ;)
Watch your curves in the FCurve editor. The default is bezier. Which will cause things to float around.
If you want something to move and then stop abruptly and/or hold position, then you need to change the interpolation between the "stopped" keyframes to Linear.
You can also use a Custom Bezier to create abrupt changes in direction. CTRL-clicking on the bezier handle with allow you to split the handles.
I am trying to go through this in baby or should I say 'binky' steps.
Sooner or later the F-Cruves will play a role from what I have read here and in the manual as well as my time in the Beta Forums. |
Post by Humdinger // Aug 7, 2008, 8:23am
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Humdinger
Total Posts: 319
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Alright here we are...
Now I am no animator but I am lazy....and an olde time TS User...
This was done in about 15 minutes...
Not sure about adjusting F-curves and all that.
Using tank girl default rig, all i did was uncheck 'pose only' on the IK handles for the feet etc. 90% of this is just from moving the three IK handles and tweaking a joint here and there !!!
Sweet !
This is poor quality but what progress gentlemen !!!
Did something directly in TS that would have taken hours to do before (if one even could ) in less than 30 minutes!
Including creating this wmv file !!!
Bravo !
My next test will be my infamous 'Walk up Stairs..and make it Quick !'
Render direct from Real-Time View |
Post by Jack Edwards // Aug 7, 2008, 8:37am
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Jack Edwards
Total Posts: 4062
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Using the FCurve editor will save you a lot of work and frustration. (Hopefully!) Seeing how TS interpolates between the keyframes as a visual line (curve) will explain the "odd" behaviors you see between key frames.
Here's a small project that I did using the FCurve editor to animate a bouncing ball:
http://forums1.caligari.com/truespace/showthread.php?t=3193
It's cartoon style with keyframes for scaling and compressing, but the point of the excercize is to learn how to use smooth and sharp keyframe transitions to achieve crisp animations. Basically you need sharp linear interpolated (or custom Bezier) keyframes for abrupt changes in direction but smooth bezier interpolations for more gradual changes in direction. |
Post by transient // Aug 7, 2008, 2:47pm
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transient
Total Posts: 977
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Hmmmmm if it was using TS 7.0+ that may have actually been an import of BVH from Poser 5 after using the Walk Designer.
Okay, I stand corrected. ;)
There's a good book by George Maestri that goes through basic walk and run cycles quite elegantly. |
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