Hi
I want to find some some IK solution to my character
have two bones,upper arm and lower arm,drawn in front view
and in the case of right arm, when I transform my R_Arm_IK solver,
my lower arm rotates from left to right,counterclockwise,
right elbow rotation.
That's fine.
But, in the case of left arm, it should rotates from right to left,clockwise,
like you bend you left hand in elbow(look at you friend,facing him)
So, probably I have to change some IK solver parameters.
But, which one?

Best regards and Marry Christmass
Ben

Good question. I'm guessing that you drew the arms two times. Since the Bones tool always orients the chain root in world space, you end up with them twisting in different directions. There's two solutions that I can think off the top of my head:
- Delete one of the arms. Use the Mirror tool to mirror your bone chain. This will produce a chain root that will be point in the desired direction.
- Manually fix the chain root by yourself. In the upper arm bone, turn on Keep Position When Parenting. Disconnect it from its chain root. Put in a -1 in the X scale of the chain root to orient the proper way. Now connect back the upper arm bone to the chain root.

Just as an aside, you can find yourself getting viewport flipping if you “home” your viewport on something with a -1 scale. This can be extremely disconcerting when you're working with objects with non-1 scales (which is often!).

How to test?
*) Create a new geometry object
*) Change it's scale to -1 to for funnier results, something wacking like 3,1,1.
*) Switch into SOPs viewer and turn to See One, in the See One/See All button.
*) Hit f or g to home to viewport.
*) Boing, your object looks regular again.
*) Hit See All and see that everything else is deformed! This is because your camera space is deformed to match the object you homed on.
*) Hit home again… ahhh.

Not to hijack this thread, but this happens frequently with mirrored objects and its something to keep in mind. (In my opinion it's a bug, because although “correct” in some ways, its totally useless and just causes confusion right now. Handles also don't look right on scaled objects, at least in 6.1.208)

Take care,
Jason

That's kinda interesting. Note that you left out the part where you also need another object in the scene to notice the effect. It took me a couple of tries before I realized that.

I thought that the scaling on the handles has been fixed in 6.1 for quite a while now. It works for me in 6.1.208 as long as you're not in the whacked viewport scaling mode.

edward
That's kinda interesting. Note that you left out the part where you also need another object in the scene to notice the effect. It took me a couple of tries before I realized that.

Ah yes, true - sorry about that. You can get some pretty interesting effects with that, being inside a space warp. Thank God all the transforms on the camera are affine (non-distorting) or you could get in a real fix.

edward
I thought that the scaling on the handles has been fixed in 6.1 for quite a while now. It works for me in 6.1.208 as long as you're not in the whacked viewport scaling mode.

You know, I thought that too. I'd must have been fixed for 5.x, because I loaded up 6.0.333 and I get the same behaviour. I don't have 5.x at home…

Happy holidays,
J