This tutorial is going to cover how you can alter the orientation of your skeleton's joints using a skeleton that we created in the previous tutorial for a human arm. I'm going to hide the geometry because we don't need that. for this tutorial.
The first thing I'm going to show you is how we can view the local rotation axis of joints. So by selecting the shoulder joint and right clicking and choosing select hierarchy this will select each individual joint in our chain. And then if we go to display, transform display, local rotation axes, Maya then shows us the orientation of each of the joints.
Now, we want them all to be orientated in the same way and also in the correct direction. We can see that we have some kind of these end joints pointing off and most noticeably our wrist joint. If I were to try and rotate this by using the Z-axis, it doesn't rotate as we see it.
we would expect. If we wanted to rotate it straight down we would have to guess where to click and we wouldn't get nice rotation on a single axis. So we need to fix this. To do this, I'm going to first orientate all the joints the same direction. So I'm going to select the shoulder again, right click, select hierarchy.
With my rigging menu selected, I'm going to go to skeleton, orient joint and I'm going to open the options. I'm just going to reset the settings so I can talk you through what each of them does. The primary axis is the axis that points down the bone.
Okay and currently it's set to x and I want to keep it as x so I'm going to leave the primary axis. This is X. The secondary axis and the secondary axis world orientation work together. And this is, you can set which you want your secondary axis to be. And then you can also set which direction you want the secondary axis to point.
So I want all my z-axis to point forward, which is positive z. So I need to select z to tell it I want to alter the z-axis direction. And then I want to point that direction in z positive.
If you watch what happens when I click apply, you'll notice... that some of my joints alter. Okay there we have it.
They're all pointing in the same direction now, a bar a few which I'll talk about now. We'll notice that that didn't fix our wrist. All that did is just make sure that the wrist was oriented to the first finger that I drew. So I need to actually make it so that it's going to rotate in line with the elbow. To do this I'm just going to select all of the next joint from down from the wrist and press shift p to unparent you can also go to edit unparent if you wanted to i'm going to select the wrist joint and with my orient joint options still open i'm going to check orient joint to world and hit apply orient joint to world means that this joint will try and align itself with the elbow, which is what we want.
So with that done, I'm going to reselect all of these joints and then my wrist and then you can either press P or you can go to Edit Parent. So we've reparented those and now when we select the wrist and try to rotate, we can grab just the Z and we have as we would expect. expect the wrist can bend. The last thing that we need to do here is make sure that the end joints orient correctly.
So with that selected, we can just do the same as we did to the wrist by using the orient joint to world and this will try and align them with the last joints in the chain before them. Hit that and they've now oriented. So they are all the same. But I just want to show you why we might want to make one more tweak.
If I select the thumb. and the fingers if I was going to animate them and then use the Z rotation. We get a nice curl of the finger and we get a curl of the thumb however it's not curling in the direction that we want.
So what we actually want to do is set different orientation settings for the thumb so that we can grab them all and use Z and the thumb rotates the direction that we want to. So I'm just going to undo that. So to reorient the thumb I'm going to select the top joint, right click, select hierarchy. I'm going to go to my orient joint options. I'm going to turn off orient joint to world.
I still want the primary axis to be the same, so I still want the X to point down the joint, just like the fingers. I still want the secondary axis to be Z. I need to orient it differently.
So I'm going to use a secondary axis of Y in the negative and hit apply. and that's reoriented the thumb. Just kind of double check that the end joint is oriented correctly.
By selecting it, orient joint to world, apply. And now, we come in and rotate using Z. We have a bend in the thumb, which is what we wanted. So there we have our arm oriented correctly.