topic Re: IK Solvers & Maxscript - Assuming Preferred Angles? in 3ds Max Animation and Rigging Forum

IK Solvers & Maxscript - Assuming Preferred Angles?

TheTrueKaiser — Thu, 07 Mar 2019 22:12:23 GMT

Hello, everyone! I hope you are all doing well!

I've got a pretty simple question that has been causing me endless frustration: How do I apply the "Assume Preferred Angles" control programmatically?

As a primer, I have been making tools in Maxscript for roughly 6 years now, so I am no stranger to the language or the documentation!

Full disclosure, I am using 3dsMax 2011 64-bit on Windows 7.

Here is a full discourse of what all I have uncovered myself:

Firstly, I am creating an IK solver in this way:

solver = iksys.ikchain oThigh oFoot "IKLimb"

Pretty straightforward, all is well and good. I further go on to apply the VHTarget of the solver's controller:

solver.controller.vhtarget = kneeDummy

And this is where my problem arises. Doing so causes the leg to rotate slightly, which I don't want. When applying the IK chain manually, through Animation -> IK Solvers -> IK Limb Solver, this is resolved easily: hit the "Assume Preferred Angles" button, and the leg snaps back to its original rotations, while still behaving correctly with the IK solving. Great!

But I can not, for the life of me, figure out how to apply this programmatically.

So the first thing I did was address the documentation for the IKChainControl class. Here, the documentation states there is a function named "assumePrefAngles()". Now, I'm no rocket scientist, but my intuition suggests to me that the "assumePrefAngles()" method is probably what the "Assume Preferred Angles" button uses, and so I want to give it a try!

So I just casually call this:

solver.controller.assumePrefAngles()

And... it errors.

"-- Unknown property: "assumePrefAngles" in Controller:IKChainControl"

Well, okay, that's not a huge deal. The documentation says that it is in part of the Action interface. Using the MAXListener to call

showinterfaces solver.controller

Yields the same information. Specifically, it yields this:

showinterfaces solver.controller
  Interface: Action
   Properties:
   Methods:
    <boolean>snap()  -- Action Interface
    <boolean>ikSnap()  -- Action Interface
    <boolean>fkSnap()  -- Action Interface
    <boolean>toggleEnabled()  -- Action Interface
    <boolean>setPrefAngles()  -- Action Interface
    <boolean>assumePrefAngles()  -- Action Interface
   Actions:
    Category: IK_Chain_Actions; Action: IK_Chain_Snap_Action; Shortcut: -- none defined --
    Category: IK_Chain_Actions; Action: IK_Chain_IK_Snap; Shortcut: -- none defined --
    Category: IK_Chain_Actions; Action: IK_Chain_FK_Snap; Shortcut: -- none defined --
    Category: IK_Chain_Actions; Action: IK_Solver_Toggle; Shortcut: -- none defined --
    Category: IK_Chain_Actions; Action: Set_Pref_Angles; Shortcut: -- none defined --
    Category: IK_Chain_Actions; Action: Assume_Pref_Angles; Shortcut: -- none defined --
OK

Now, I will be the first to admit I don't know what this "Category: IK_Chain_Actions" malarky means, but that doesn't distract me.

I know from experience that the IKSys Interface is called in the form of IKSys.<method> . In fact, I can peek at the entire IKSys interface with showinterface:

showinterface IKSys
  Interface: IKSys
   Properties:
   Methods:
    <node>ikChain <node>startJoint <node>endJoint <string>solver
    <integer>solverCount()
    <TSTR by value>solverName <integer>solverIndex
    <TSTR by value>solverUIName <integer>solverIndex
    <void>suspendLinkNotify()
    <void>resumeLinkNotify()
    <bool>isLinkNotifySuspended()
   Actions:
OK

And we clearly see the "ikChain" control listed, beneath the "Interface: IKSys" line. We know for a fact that "iksys.ikchain" works, because I am using it to create the IK chain in the first place.

So then intuition suggests to me that to call the assumePrefAngles() method, that is inside the Action interface, that I need to call it via Action.assumePrefAngles(). So I do that.

"-- Unknown property: "assumePrefAngles" in undefined"

Well that's unfortunate. I'll just peek at the Action interface, which I know exists because showinterfaces solver.controller dumps the interface for me. So I run showinterface Action.

"-- No ""showInterface"" function for undefined"

Oookay... Let's just see what Action itself is, by simplying running Action in the MAXListener...

"Action
undefined"

Oh. Well, that explains a lot.

But, unfortunately, it doesn't explain how I'm supposed to actually call the assumePrefAngles() method. I have scoured the Internet for the past 90 minutes, and I simply cannot find any information on this.

I've exhausted all of my resources but one: all of you find ladies and gentlemen here at the forums. I am hoping that, if no one is able to yield the golden answer, then I can at least be pointed in a new direction in my hunt for this elusive knowledge.

Thank you all very much for taking the time to read this post and consider my plight! I look forward to hearing any thoughts or suggestions you fine people may have!

Re: IK Solvers & Maxscript - Assuming Preferred Angles?

ads_royje — Fri, 08 Mar 2019 11:45:06 GMT

Hi @TheTrueKaiser,

I agree, documentation is not clear on the subject.

I currently do not have Max 2011 installed but I have 2012.

I tried below with success in 2012.

Can you give a try to :

showinterface IKChainControl.IKChainActions()

It should print:

Interface: IKChainActions
Properties:
Methods:
<boolean>snap() -- Action Interface
<boolean>ikSnap() -- Action Interface
<boolean>fkSnap() -- Action Interface
<boolean>toggleEnabled() -- Action Interface
<boolean>setPrefAngles() -- Action Interface
<boolean>assumePrefAngles() -- Action Interface

With the IKChain object selected, you should be able to use :

IKChainControl.IKChainActions.setPrefAngles()
IKChainControl.IKChainActions.assumePrefAngles()

Let me know if this helps or not,

Regards,

Re: IK Solvers & Maxscript - Assuming Preferred Angles?

TheTrueKaiser — Fri, 08 Mar 2019 20:55:00 GMT

Hey Royje!

It seems like the interfaces might have changed between 2011 and 2012, because unfortunately, running

showinterface IKChainControl.IKChainActions()

On a fresh session of 3dsMax, with nothing created or selected, returns the following error:

showinterface IKChainControl.IKChainActions()
-- Unknown property: "IKChainActions" in IKChainControl

HOWEVER!

If I probe IKChainControl.snap directly, just to see if it exists, it returns that it is, indeed, a function. This is one of the functions listed in the interface when I tap the IKChainControl interface. Similarly, assumePrefAngles returns as existing here as well:

showinterfaces IKChainControl
  Interface: Action
   Properties:
   Methods:
    <boolean>snap()  -- Action Interface
    <boolean>ikSnap()  -- Action Interface
    <boolean>fkSnap()  -- Action Interface
    <boolean>toggleEnabled()  -- Action Interface
    <boolean>setPrefAngles()  -- Action Interface
    <boolean>assumePrefAngles()  -- Action Interface
   Actions:
    Category: IK_Chain_Actions; Action: IK_Chain_Snap_Action; Shortcut: -- none defined --
    Category: IK_Chain_Actions; Action: IK_Chain_IK_Snap; Shortcut: -- none defined --
    Category: IK_Chain_Actions; Action: IK_Chain_FK_Snap; Shortcut: -- none defined --
    Category: IK_Chain_Actions; Action: IK_Solver_Toggle; Shortcut: -- none defined --
    Category: IK_Chain_Actions; Action: Set_Pref_Angles; Shortcut: -- none defined --
    Category: IK_Chain_Actions; Action: Assume_Pref_Angles; Shortcut: -- none defined --
OK
IKChainControl.snap
snap()
IKChainControl.assumePrefAngles
assumePrefAngles()

This indeed got me onto the right track!

The following block of code correctly assumes the preferred angles, and resolves the problem that I've been trying to resolve:

		select ikEffector
		IKChainControl.assumePrefAngles()
		deselect ikEffector

There is, however, a minor caveat: If this code is called in the same chunk that creates the IK Chain, EG:

		-- Create the IK chain
		ikEffector = iksys.ikchain oThigh oFoot "IKLimb"
		ikEffector.controller.vhtarget = kneedummy
		
		-- Assume preferred angles, to stop the leg snapping when the VHTarget is set
		deselect selection
		select ikEffector
		IKChainControl.assumePrefAngles()
		deselect ikEffector

Then the operation appears to go too fast - the "assumePrefAngles()" won't have any effect, and the leg will rotate incorrectly, just as before. If I wait until the function creating the ikEffector returns, and then call the assumePrefAngles() chunk in the MAXListener, it works correctly.

I know this is beyond the purview of this question, but I figure I might as well ask for posterity:

Is there a way to make Maxscript wait for a method to complete, before executing the next instruction? In this case, I suspect waiting for the iksys.ikchain control to fully complete would resolve this issue.

I would separately love to have the ability to wait for Skinwrap to complete - I have tools that utilize it, and I had to break the automation up into separate buttons the user manually presses, because otherwise the script runs too fast, and executes instructions before the Skinwrap completes.

Re: IK Solvers & Maxscript - Assuming Preferred Angles?

ads_royje — Mon, 11 Mar 2019 15:20:49 GMT

Hi @TheTrueKaiser ,

I installed 2011 to be able to try too.

As you figured out already, indeed, in 2011 the interface is different then 2012 and forward.

I am glad to read this helped you get unblocked anyway! 🙂

With a little mxs code, I was not able to reproduce an issue with some mxs race condition.

Usually, when maxscript runs too fast for Max, I use ForceCompleteRedraw() and that helps.