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View Full Version : Rotational Joint Limits not working how I want (in 3ds Max)


chillyche
10-22-2008, 03:05 AM
So, I have a robotic arm which features, in addition to an elbow, another joint which allows twisting of the fore-arm. when I limit that particular bone's Rotational Joint around the Z-axis (the axis that it needs to rotate around to twist in this case), it seems to be limiting it to the World Z-axis, not the object's Z-axis. I can't figure this out. any ideas?

uiron
10-22-2008, 06:06 AM
seems like you didn't pick the right axis to limit after all. select object you want to limit, select rotate tool and set it's rotate space to "gimbal". now you can see how your euler rotation planes are aligned and which channel represents which rotation in space.

wamo
10-22-2008, 08:20 PM
So, I have a robotic arm which features, in addition to an elbow, another joint which allows twisting of the fore-arm. when I limit that particular bone's Rotational Joint around the Z-axis (the axis that it needs to rotate around to twist in this case), it seems to be limiting it to the World Z-axis, not the object's Z-axis. I can't figure this out. any ideas?

If i did understand what you mean well, then the answer is, just you need to limit the Object's Local Z-axis insted of its world Z-axis,and you need to make a parent for the joint you wanna limit which the parent transform should be aligned to the joint you wanna limit, now you have changed the limitation coordinate from world to Local.

chillyche
10-22-2008, 10:29 PM
If i did understand what you mean well, then the answer is, just you need to limit the Object's Local Z-axis insted of its world Z-axis,and you need to make a parent for the joint you wanna limit which the parent transform should be aligned to the joint you wanna limit, now you have changed the limitation coordinate from world to Local.

So does this mean that, for example, if I have a shoulder and an upper arm, and I want the upper arm to twist around the Z axis for some reason, that the shoulder's Z-axis has to be aligned to the upper arm's Z-axis?

uiron
10-23-2008, 08:00 AM
basically, yes, this is how euler rotations work, actual value of object's rotation represents value "how much object is rotated compared to it's parent".

however, you CAN do what you want without aligning parent bone at all. i can't see your scene, but if object's local Z axis is the one you want to twist around - do a little trick, change object's euler rotation order to ZXY or ZYX (you might have to realign your object as it might change it's orientation by doing this). because of how eulers work, Z is now taking effect only after Y and X rotation was made.

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