Bongo2 IK precalculated settings


Please, help with simple IK animation problem, or get link to answer.

I have IK animation with short hierarchy. Separately parts work good, but in whole hierarchy have “Constraint goal not reached”. Then after Precalculate IK at the end of timeline all objects reach a success at it places and orientatios. I have mind that Bongo have settings about Precalculated IK or similar besides IK settings in Document Properties/Bongo. But I don’t now where it placed.


Probably it is merely what the error message says; a constraint goal that cannot be reached at some point.
Please post the model so I can have a look. If confidentiality is needed you can send it directly to


Luc, thank You for help. Animation is not confidential, it’s a training. I’m learning bongo now.

At this scene I have 3 steps.

At first step objekt “Box” stay down.

At second step object “t1” rotate up around X axis, and objekt “Box” move vith it.

At third step object “platform” rotate around Z axis with “t1”, “box” and “door”, and becouse of constraint object “t2” object “door” oppen up. But on playing animation step three don’t reach success.

But after precalculated IK at the end of animation, all good.

Maybe trouble in IK settings of object “T2”: joint universal, rotate free at “X” and “Z”. Pivot along object axis.

test.3dm (1.0 MB)

I’m not 100% sure what’s bothering the model. I guess it has to do with the fact that the model contains 2 IK chains (which you can observe in the commandline when IK is being solved)


and that the result of one chain depends on the result of the other.

In your model you can notice that running the solver (“BongoPreCalculateIk” command) with the timelineslider a tick where the “Constraint goal not reached” notion appears, clears the situation for that tick in particular (but not for the entire sequence). Augmenting the number of Precalculation samples merely alters the ticks the misfitting occurs.
I think you found the Bongo setting yourself.

I assume you first build the chain concerning the box and door, and afterwards added the chain with the rotating platform. I guess (correct me if I’m wrong @Joshua) that therefore the box/door chain is solved first and the platform part secondly, whereas it should be the other way around.

In the model test 000.3dm (960.7 KB) I have rebuild the chains from scratch, but now in the ‘correct’ order; first the rotating platform and then the box/door stuff… and bingo!
And notice that 100 Precalculation samples suffice.

There is a very old bugreport ( pleading for the ability to choose which IK-chain Bongo should calculate first. Could be very useful in this model.


PS. Being a apprentice, you did a fine job on the IK :clap:

Luc, wery thanks for your answer and file. I rebuild chains how You showed. Now I understand what was my trouble. But if to look at end tick, state of object “Box” is bottomer them I need. (Look to the picture). It because object “t1” rotate with object “921” now. This problem I solwed with new key for “t1” at the end of anivation. But if it can, I want do it without this.

About sequence of my steps at create hierarchies, it was: First I was create chain with object “t1” and Box. Then I separately was create chain with object “door”. Then - with object “platform” and object “t2”. After set keys for chains with box and platform, I put chain with door to chain “box”, and then put chain “box” to chain “platform” in amimation manager. After thet I did join constraint points inside all chains.

may be You will be interesting, but at one of my kinematic file with it algoritm the animation has not error, and the end states of all objects are good. But in this kinematic design rotating objects is not intersect at its ways. I don’t naw how it can be important. Link the file:
1.3dm (908.7 KB)

Thanks for your praise. I think that it may be becouse interface ofbongo is sinple for undersanding

Thanks to your 1.3dm model I think I understood the purpose of your project.
I have explored some different chain structures to get around the tilting of 921, but I keep on bumping into the issue of reciprocal constraints.
Then it came to me that the use of Expressions to compensate the rotation of Object 921 might be a solutions. And it does. test 001.3dm (963.9 KB)
Maybe this is a solution for you?

Then I had a go at your enigma with the Connections of Bongo’s WIP (Rhino - Download - Bongo for Windows WIP). test 301.3dm (970.3 KB)
It’s a peace of cake.
Note that the lifting of the box is initiated by keyframing the “t1/platform” connection.


BTW by means of the BongoVersionSwitch you can switch in between both Bongo versions without uninstalling or anything.

Luc, sorry for a long time answer. I was learned your decision with expression, its realy wery simple and it’s give the desired result for me. Don’t no why I didn’t understand this myself))). Wery thanks. About WIP Bongo, I can’t tell you about my experience of it, because I don’t have the opportunity to work with it now. But I will try do it at short time.

Wery thanks for Your help!

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