inverse kinematics

[sparky]

Guys (n gals)

Anyone have experience of linking objects through inverse kinematics in VIZ (i think this is how i need to get round a certain problem but have never really used this function in VIZ before)

Ok, I have a standard VIZ pivot double door. I have created a couple of handles for it and want it to be attached to the door and pivot when the door opens so the handles move with the door. I am looking at walking up to this building as an animation and then the doors open as you approach. It would be really good to get a better understanding of how this could be acheived. I presume you need to go down the road of inverse kinematics to achieve this but was wondering if anyone could enlighten me? is there a quick way to do this.

cheers in advance

sparky

[charleyc]

What you would want is Linking, not so much IK. IK is a hierarchical solver for when you have a series of Linked objects (a Hierarchy) of say, a leg and foot. In FK (Forward Kinematics), you would rotate the thigh, then the calf, then the foot to place it where you want. IK is where you can simply grab the foot and move it, and the rest will follow. But for a doorknob on a door, you need to simply Link.

That being said. The Door and Window objects within Max/Viz are based on subObject animation. Simply Linking will not work. You need to use an Attachment Constraint, which will allow you to constrain an object to a specific Face of another object. The best way to do this is to apply an Edit Mesh modifier on the door, and select the face where you want the Door handle. There is a readout under the Selection buttons in the Control Panel that will tell you the face index you have selected. Then, delete that modifier, and apply your doorknob to the door with the Attachment Constraint. In that, you will have a place to enter the Face number, enter the index number you got from the Edit Mesh and using the little triangle with the red cross, align the door know to the exact place you want. A real cool thing about that is that if you have several doors, you can copy both the door and the door handle and it will create a new constraint between the two. And as long as you don't change the number of faces in the door, you can even re-size it.

A common alternative is to detach the door from the frame, ensure that the pivot is in the correct location and Link the door handle to the door and manually rotate the door open or closed.

Each method has its pros and cons.
I hope this helps you.

[sparky]

What you would want is Linking, not so much IK. IK is a hierarchical solver for when you have a series of Linked objects (a Hierarchy) of say, a leg and foot. In FK (Forward Kinematics), you would rotate the thigh, then the calf, then the foot to place it where you want. IK is where you can simply grab the foot and move it, and the rest will follow. But for a doorknob on a door, you need to simply Link.

That being said. The Door and Window objects within Max/Viz are based on subObject animation. Simply Linking will not work. You need to use an Attachment Constraint, which will allow you to constrain an object to a specific Face of another object. The best way to do this is to apply an Edit Mesh modifier on the door, and select the face where you want the Door handle. There is a readout under the Selection buttons in the Control Panel that will tell you the face index you have selected. Then, delete that modifier, and apply your doorknob to the door with the Attachment Constraint. In that, you will have a place to enter the Face number, enter the index number you got from the Edit Mesh and using the little triangle with the red cross, align the door know to the exact place you want. A real cool thing about that is that if you have several doors, you can copy both the door and the door handle and it will create a new constraint between the two. And as long as you don't change the number of faces in the door, you can even re-size it.

A common alternative is to detach the door from the frame, ensure that the pivot is in the correct location and Link the door handle to the door and manually rotate the door open or closed.

Each method has its pros and cons.
I hope this helps you.

Hi Charleyc

Many many thanks for the info and spairing the time. Sounds exactly what Im looking for. I'll try what you've explained and get back to you if anything in this process is bemusing me.

Cheers

Sp

[sparky]

ok charleyc, i had a go at using the attachment constraint to create a link between objects and it did connect to the selected face. However, it moved the orientation of the handle so that although it is sitting on the face it isnt aligned correctly. You can then rotate the object to align with the face but you cannot move it on the face you have selected (even if you try and move the cross within the little red triangle you mention.......) Any ideas what Im doing wrong??.....It may be that Im having a blonde moment but cant seem to get things to work completely properly as yet.....perseverence may be the key on this........

[mike_kennedy]

detaching to seperate objects will be the easiest way to do this, just setup your new pivots on the new objects, use the link tool and go. For the Attachment trick, try attaching a dummy to the face, then link your door handle to the dummy......but leave in space where you want....

[charleyc]

I cannot say for sure what your problem is without seeing your file, and even then I have Max, so there could be an issue with Viz.

[sparky]

detaching to seperate objects will be the easiest way to do this, just setup your new pivots on the new objects, use the link tool and go. For the Attachment trick, try attaching a dummy to the face, then link your door handle to the dummy......but leave in space where you want....

Thanks for the tips guys. This is what I ended up doing in the end.....