FK/IK blending FK not returning to original position?
Posted: 12 March 2018 09:19 PM   [ Ignore ]  
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Hi

Iv been working with IK tag using the IK/FK blending to take full advantage of the system.  Now I have controllers set up for fk use and these controllers are assigned from each bone using PSR constraints.  For the IK/FK blending to work these two system go againts each other so I set up the blending slider to drive the strength between turning off the fk constraints when in IK mode, and vice versa.

If I pose the IK into position then blend back to FK the joints should return but they dont so what am I missing in the expresso set up, do I need two rigs to do this correctly?  If I choose to make the controllers a child of the bones (ik oddities children.zip) instead of using psr constraints (ik oddities.zip) then the problem is gone?

Thanks.  Dan

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ik oddities.zip  (File Size: 62KB - Downloads: 62)
ik oddities chidren.zip  (File Size: 67KB - Downloads: 51)
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Posted: 13 March 2018 12:40 AM   [ Ignore ]   [ # 1 ]  
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Hi Dan,

Please check out this series:
https://www.cineversity.com/vidplaylist/ik_fk_arm/ikfk_arm_part_1a

Please check your file, to have a PSR and a Protection at the same time makes not a lot of sense: What do I miss.

Learn from Bret, he is the Master in that.

All the best

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Posted: 13 March 2018 01:51 AM   [ Ignore ]   [ # 2 ]  
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Dr. Sassi - 13 March 2018 12:40 AM

Hi Dan,

Please check out this series:
https://www.cineversity.com/vidplaylist/ik_fk_arm/ikfk_arm_part_1a

Please check your file, to have a PSR and a Protection at the same time makes not a lot of sense: What do I miss.

Learn from Bret, he is the Master in that.

All the best


Hi

I put protection tag on for restrictions on the constraints that are not in use such as position.  In either case the issues is still there.  The video link you quoted iv seen its not
Using the ik tag with blending but is a manual ik fk its for for people who don’t have studio.  Iv not found any video showing the ik fk slider blend for use on a rig with fk controllers.

Thanks.  Dab

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Posted: 13 March 2018 02:48 AM   [ Ignore ]   [ # 3 ]  
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Dan,

I tried to understand what you want to set up, hence my suggestion to watch the series, as he discusses the problems inside of the IK/FK chain in detail there. OK, let’s ignore this.

Have you checked out the data on the IK Advance tab, as in

•Keep Goal
•Update on Goal
•Constrain Goal
•Align Goal
•Update Ik on FK

Is that something you like to develop?

I’m obviously not clear about this statement:
“If I pose the IK into position then blend back to FK the joints should return but they dont…”

Return to the state before the IK was used?

Sorry when I’m not following here.

Cheers.

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Posted: 13 March 2018 03:40 AM   [ Ignore ]   [ # 4 ]  
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Dan,

Perhaps the rig I posted helps.
https://www.cineversity.com/forums/viewthread/1900/#7167

Scroll down. Post #10. I invested an hour googling again if I missed anything new in that regard. I don’t - so far I can tell.

The switch IK2FK or FK2IK is something one can find in the Character Object. The IK/FK slider, is a blend (from where I look at it), between the three joint chains that are normally used to explain it. I would use it after each of the two information containing chains is completed and then blend the result.

All the best

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Posted: 13 March 2018 04:02 AM   [ Ignore ]   [ # 5 ]  
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Dr. Sassi - 13 March 2018 03:40 AM

Dan,

Perhaps the rig I posted helps.
https://www.cineversity.com/forums/viewthread/1900/#7167

Scroll down. Post #10. I invested an hour googling again if I missed anything new in that regard. I don’t - so far I can tell.

The switch IK2FK or FK2IK is something one can find in the Character Object. The IK/FK slider, is a blend (from where I look at it), between the three joint chains that are normally used to explain it. I would use it after each of the two information containing chains is completed and then blend the result.

All the best

Thank you for your time on this as always, I appreciate your efforts.  I havent checked out the file yet just got home but I will.

To clarify the problem.  The IK/FK blending slider built into the IK tag works fine, but things get rather complicated as soon as you wish to have spline controllers assigned to the joints for FK.  In the example file I posted what should happen is when the IK goal moves the rig into a new position then the I use the IK to FK blending the joints should return back to the fk position.  In my file when I move the IK to FK blend slider the joints to not fully return back to the FK position, and whats more when I move the slider slow it alows the joints position when returning back to FK move closer to its original position as to when I move the slider fast it stops short.

Now the second file I posted (ik oddities chidren.zip)  this has the same set up but the difference is the controllers do not need to be constrained back to the joints with a positional constraint as I placed each controller as a child to its respected joint hence when the joint moves, so does the controllers, where as when they are not parented in this way a positional constraint is needed.  The reason why the positional constraint is needed is because the IK takes full control over the joints and will leave the fk controllers behind.

Them options I will look into now, as maybe, just maybe the answer is in there. 

Thanks again, Dan

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Posted: 13 March 2018 06:47 AM   [ Ignore ]   [ # 6 ]  
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Thanks, Dan, for the addition information.

The child based idea gave me the feeling that I really don’t know what your target is. Now I understand. As a side note, I try to read between the lines, or better: between the objects wink, here in the forum. I try to imagine what is known, what is wanted, etc. In the past fourteen years that has worked for me, and sticking to scene files as answer. Besides, I never assume that things stay the same.

To rotate a child object and have that information forced on the parent object has an effect on the child object of course. How that will work for editor and render at the same time, I’m not sure at all. The editor is update frequently, the render only once.

When I mentioned Bret, then for a good reason. There is so much in the Character Object, that carries his and of course many other peoples “handwriting” in terms of rigging, that I search in the Character Object for help when I get uncertain, hence my credit that I give.

Please have a look to the clip below
https://www.amazon.com/clouddrive/share/zrjYyr2Svn1TgZF8koCJFwAwhWZ2SBd4j0NymdqAwPL

The series of Bret’s Character Template Building, gives a clear idea about how to open and set up those templates.

Perhaps that will help to get things working as you need them.

All the best

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Posted: 13 March 2018 10:27 AM   [ Ignore ]   [ # 7 ]  
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P.S.: I guess this is the shortest and simplest version, if I understood your request correctly, that I can come up with.

In short, this solution uses three Xpresso Tags, two to transfer information and one to switch either the first or the second one off.

One moves the information from the spheres to the joints.
The other one moves the information from the joints to the spheres.
The third one just enables one and not the other (vice versa) and if not enabled, no interference.

To switch click on the Root_UD null object—>Attribute Manger> User Data.

Scene file: [sketch]
https://www.amazon.com/clouddrive/share/cI91GGkkhfbibi7R1SVGITdKuOH8rpkRoDRDqOkrNLE

(What really throw me off today was the child/parents set up, I couldn’t really see anymore where you wanted to go with this.)

I hope that works for you.

All the best

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Posted: 13 March 2018 02:59 PM   [ Ignore ]   [ # 8 ]  
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Thank you.  The file you made was a nice set up which gave me another option which I asked for a while ago, to let the IK set the position of the joints, and stay there when switched to FK to take over, very nice, however this file also highlited my problem in that the way Modo and the character object works correctly, the ik/fk blending should allow the FK to retain its original position.

See image to highlite the differences between character object, your rig an my rig.

1: Character object alows me to pose FK, blend to IK, move IK, and blend back to FK orginal position (Correct)

2: Your rig does not allow me to pose FK, blend to IK, move IK, and blend back to FK original position, if fact without moving anything, and just using slider between IK/fk rig collapes or reforms to an entirly new position in which neither was the IK or FK positioned too, it failed at step 2.

3: My rig acts like character object, but only If I use FK first to be different to IK default position.  I can blend between IK back to FK and the FK original position of joints are kept (Great!)

4:  My rig but this time I do not make any changes to FK joints position, I leave it so both FK and IK are the same.  I move IK to repose the joint chain, and then try to blend back to FK, but this time the FK does not go back, whats worse is depending as to how fast I use my IK/FB blending slider is to how close the FK gets to its original position.

In the ideal world id like the FK blending slider allow the FK joint positions to remain all the while the slider is set to fk, and no matter what I do to the IK it has no impact on full FK.  Id then like as in your rig to choose to force the FK to match the position of the IK for seamless transition between the two using a button/swicth named such as (Match IK to FK)

Image link below.

https://i.imgur.com/88FAf8l.jpg

PS: Im a idiot.  The only error I made was I used a position constraint to keep the controllers to the joints when using IK, no wonder when I blended back to FK the FK position was lost, the FK controllers where moved by the IK, but its still odd that as a function the IK repositioning of the FK controllers where not retained, so maybe the global matrix as what you used is the answer .

So in short I removed the FK postion constraints to the joints when in IK mode when left the FK controllers behind “as in the character object”  but should I wish the FK to follow the IK positioning of the joints this too would serve as a function, one im yet to work out.

Thanks, Dan

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Posted: 13 March 2018 10:32 PM   [ Ignore ]   [ # 9 ]  
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Hi Dan,

We have two complete different ideas about how this is supposed to work. (Yes, I read through and the P.S., thanks for the update.)

I should have linked the buttons to the slider, (either 0% or 100% ) but my impression was that one has then to unlink them as well later on: so I choose the simpler version. And that has send you in trouble. Sorry.

This set up (not a rig, I named it clearly sketch!) was supposed to either have the joints follow what the Spheres, or what IK does; With the slider each time acknowledge this, with 0% (IK) or set to 100% (FK).
The use of the opposite was certainly not intended.

For me, and I have yet to find a reasonable source that tells me otherwise, the blend is always during keyframe setting on the position 0% or 100%. When those keys are set, the Blend might be used to smooth out the two given results. Hence the suggestion to watch this series above, that shows the raw set up.

You wanted a solution that allows the Spheres to either follow the Joints or the Joints follow the Sphere. That is exactly what this suggestion does. Except the slider works against it.
For now, I really don’t know what else to do.

If you explore the Character Rig, you will find that there are two Joint hierarchies, one for FK and one for IK, again and I know you don’t intend to watch it:  like said in Bret’s series…
I will try again with a tutorial suggestion: It is on my mind since you asked but since it is as well to a certain degree limited, I hesitated, perhaps use it as brainstorming.
https://www.cineversity.com/vidplaytut/bi-directional_constraint
As well here, you might notice all the cautions that Kai tells. So far, I think the Character Object has the most pristine solution, and yes, it is complex. To simplify from the working version might have always the danger of problems along the way.

Good luck with your exploration.

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Posted: 13 March 2018 11:00 PM   [ Ignore ]   [ # 10 ]  
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Thanks for your help.  Im sure you know what happens to the brain after 12 hours each day flat out, the mind starts to loose its edge even for the more simple things.

Ib been looking at the character tool IK/FK switch and for the life of me cant get it to do anything lol, is it documented as I cant find it in user guide?  It looks like there is some kind of order in which you use it, get that order wrong it seems to do nothing.

Im watching through this maya set see what I can get from that.

http://lesterbanks.com/2017/07/fundamentals-building-fk-ik-switch/

Dan

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Posted: 13 March 2018 11:26 PM   [ Ignore ]   [ # 11 ]  
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Thanks for the feedback, Dan, yes I agree, we called it Cat-Brain back in the days, after too many long days in a row, with too much output and too little of anything else.

On my pre-order list is another book, announced for the end of the month. Again a “Character Animation” book, this time from another Disney instructor. Fingers crossed that I will get something more out of it, than the last book. Which left exactly this field of your current exploration completely blank.

The manual tells not a lot, and it leaves it to a certain degree to interpretation, which makes me uncertain. (I never assume that I know it or that I’m right, as I’m consider that as the end of my development. My big no-no word is: I know that. My biggest term for progress is: What if…? So, I stay open, try to read the scene files, and the text in the forum, try to mix that with my past 14 years of reading forums question and then let the brainstorming begin how to find something.

Anyway, this is from the R19 Help Content:
IK/FK [0..100%]
Allows you to blend seamlessly between the chain’s current FK pose and the pose calculated for the chain by the IK solver.

No word when to blend. So, I can’t pinpoint if one could leave the slider at 37% while in Auto Key mode, and move on with animation all kind of stuff.
My idea (again, I’m happy to find something more elaborated as source, than I have in any of my trainings so far or books) is, that one blends after the keyframes are set. If one has the slider anywhere between 0.1% and 99.9%, then keyframes things, what is the use of the blend, when that position is key-framed on both sided (FK and IK).

Going further, I think that the IK will solve on many variables, and so the FK (if we match one or the other) should follow the IK, and not the other way around. So, if we want to continue from a IK situation, we can align any Joint in FK very closely to the IK joint locations. To line up an IK to the FK, not so much, talking about precision, hence the blend option.

In short, my ideal and idea is, to use the blend slider either full IK or full FK during key-framing, and for the final finish, to use -if needed at all- the Blend slider. Do I think this is the last word on it, absolutely not, but so far I have seen anything else, and I invest money again in a $50 book to update my knowledge. (No, it is not a C4D based book, so some stuff stays blurry and fuzzy for me, perhaps.)

In all of that, I try to follow your ideas and hope to find answers. grin Let me know if anything from post #9 helped at all.

My best wishes

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Posted: 14 March 2018 12:30 AM   [ Ignore ]   [ # 12 ]  
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Thank you again, your help is much needed, and appreciated.

Being Im not a animator “yet” I havent developed the dicipline to know what works best in the animation pipeline, however this is the way id imagine things to work.

Lets that your character wishes to grad a object from the shelf above him.  Id use IK to the the hand there.  He grabs a object but I wont want to use IK to bring the hand back as I want him to take a different route to another location while his arm is there only he will move just his forearm, and hands.  To get this to happen I would think id use IK to get the arm there fast, then rather than use a IK/FK blend, I use a switch, but blend would be fine if I could get the FK controllers to match the current joints position so when I blend or switch back to FK the FK controllers are in the same location as where the joints where left by the IK controller, hence no popping, not odd movement, and certainly no reverting back to the previous FK position where the arm was down.

I followed that Maya, but I got as far as seeing its a 3 chain manual fk/ik Blend, the same I think as one of the links you posted for C4D.  Looking about it seems this is a scripting job, but that IK to FK and FK to IK switch in the advanced character biped should be doing what I want, but it does nothing?

I will go through all you posted to make sure I didnt miss a think

Thanks, Dan

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Posted: 14 March 2018 01:47 AM   [ Ignore ]   [ # 13 ]  
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Dan,

A good and detailed education in animation is a process . I wish I would have the “grands” to take the http://www.animationmentor.com classes, but I don’t. (Kai and Bret did those and their career shows it.) There (AM), it is assumed to get through it, takes two years, or at least 1.5years for the basics.
So, what can Cineversity deliver and what can we do here in the forum? Certainly aiming to get as much as possible shared and communicated. Bret has certainly shared a lot here.

Your example, I would go with the IK as far as possible, and if you find the need to go FK, use the “Reset FK”, blend to 100% [FK] and go from there. The Blend in my book is not in any way to use during key-framing the IK nor the FK solution. It would not only limit the use and capacity of the Blend, it creates a weird overlap. Anything I said above already, I know.
In my imagination, the IK Tag builds up two copies internally. The result is supplied to the third (or originally) and which is the one in the scene visible. Similar is the Character Object set up.
So, while you key frame, as mentioned, any keyframes set while the slider is not to the left or right, will NOT allow for this frame to blend properly (edit: as in only limited), to use this slider the IK needs to be set, then the FK, purely, not at the same time.

Please have a look at the set up that the Character Object provides. 
https://www.amazon.com/clouddrive/share/IZH9goRagvK8EsSLVKb8RaonApILopssbq5TZtNO1la
The whole rig certainly not short on ingenious solutions, and yet, it works with an IK, FK and a Blend [BLND] hierarchy. So, if a simple PSR solution would have solved it, wouldn’t you think it would have been used instead of adding three times the joints plus an immense amount of nulls, etc, to that system? I really don’t think that they missed the point here. But, yes, I’m always open to explore and try to share what I can, even as sketch, which I consider is part of motivating the brainstorming process. So, in that sense, I’m happy about any discussion as it helps in so many ways the process of sharing the process “inner logic” of the whole.

My best wishes

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Posted: 14 March 2018 02:56 AM   [ Ignore ]   [ # 14 ]  
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Brilliant information, thank you.  I watched the recommended Brets video on IK.FK and have learnt some very usefull set ups and slightly different ways to do things.  I was aso very happy to see some things iv done fro my own experimentation’s is what Bret recommends so that gives me a bit more confidence in my rigging journey.

The Reset FK, man if id know that, it does the job, sets the fk to where the Ik placed the joints, awesome.  Iv learnt a heck of alot in the last 17 hours, thank you.  I will also check the rig you just posted tomorrow.

A rest for my brain now.

PS: AM thats very expensive, but you get what you pay for.  As for me Rigging/Animation is a bolt on of knowledge which will be on going, but I cant neglect where my target expertise are, so its difficult to be a jack of all trades, and a master of many, one mastery will be fine for me, its a on going learning experience, and Im not young no more so need to priorities where Im spending my time.  What I have learnt is if time is of essence its well worth paying to training by experts in their field.

Dan

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Posted: 14 March 2018 03:06 AM   [ Ignore ]   [ # 15 ]  
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This is very nice of you, Dan, thanks for the feedback: Yes, if in doubt about CA, reverse-engineer Bret’s work or watch his stuff, never a waste, not at all.

Enjoy your rest, twelve hour shifts will otherwise take a toll.

Here is a short workflow example, and of course not the one and only way of how to do it: (Scene file and screen capture clip)
https://www.amazon.com/clouddrive/share/bTpR3tGHNChlQXDxkB2Vg0BFrnKnnU59bERjPmUDq7S

Have fun with your projects.

P.S.: Not the last word, but perhaps it is, checking your idea to influence the single IK-Tag based Joint-Chain with extra objects, seems to end in a priority problem. This problem doesn’t seem to be not solvable (Again, single joint chain IK).
If we take a look at IK/FK 0% or 100%: In those extreme situations the PSR could be disabled or not. However – where I have found no solution so far is when the slider goes between 0 or 100%. It is not done with limiting the influence of the PSR, after all, the higher priority will take over the situation, and might not eliminate the prior influence fully.
I assume that the handles will carry the keyframes. If they done’t have to carry the keyframes, and the Joints hold their FK keyframes, then there might be a chance, but it feels then a question of how much complexity one likes to introduce for a very tiny comfort. I guess to establish an visual selector and go with the Axis bands seems just more feasible. Or just use a Selection Object, to activate the joints from a different point.

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