I have been trying to animate some poses for a character, but I get a bad result when my character tries to kneel down or stand up: the armatures rotate to assume the pose, but my character does not stay in the correct place during the transition from one pose to the other.
If there were a way to define vertex keys based on a pose, I could set up a number of vertex keys to accommodate a better transition. I’ve tried to do this, but failed because changing the armatures simply deform the mesh, and don’t change any actual data about the vertices. You cannot permanently apply the armature’s deformations to the mesh when the mesh has vertex keys, so that route didn’t work either.
It’s a little hard to visualize your difficulty. Could you post some images as illustrations?
Also, the main purpose of an armature is to “simply deform the mesh.” Having that work as you want it to requires proper mesh design & proper vertex weighting. Some deformations are difficult to achieve cleanly and can require “corrections,” and shape keys (is that what you mean by vertex keys?) are useful for that, but usually the armature handles the major alterations to a mesh when animating.
Oops, you’re right, Shape Keys are what I was trying to describe. I’m having some trouble uploading the screen captures for a nice example I have set up, but it depicts a character lying down to begin with, who then comes to a kneeling position. The trouble happens in the middle of that animation, when the characters’ knees go through the floor a little bit. The character ends up in the right position, but the transition wasn’t very believable. I was thinking that using shape keys for those poses could solve the problem, because the vertices would travel straight to where they need to be, rather than in circular arcs. The mesh may deform a little, but I could try several poses in the middle to clean that up.
The problem is that I’m having trouble “copying” the pose into a shape key, which could immediately solve my issue.
Thanks for your help!
PS: Is there another way to post images? I get an Error #2038.
The image-posting error may have something to do with you having a low post count since you’re a fairly new forum member – some kind of a security thing to prevent spam. After a certain post count you can attach images and put links in your posts. Sorry, I didn’t think of that earlier. And “Welcome,” by the way!
I did a very similar sequence in my short movie Kata (link in my sig), and found the action needed a larger number of intermediate keyframes than for less demanding motions, since the body’s center of gravity and weight distribution went through some complex changes. I recall having to keyframe on the threes (every third frame) or even less in some parts. I can’t say if that’s a solution for you without seeing a bit more about your action. But one tip I can pass on is to render your frames out with frame numbers (see the “Stamp” options in the Render pane), then pinpoint the frame where the error is greatest and correct for it, check the problem area of the sequence again, and correct as needed. This way you can “focus in” on problem frames. Often times I found things such as knees into the ground required only a small tweak to a single bone like the pelvis/hips, since it’s instrumental in determining body position.
That depends a lot on how you’ll be using the Pose Library. But I’d venture to say yes, keep them out. They are there to compensate for the normal dislocations that can occur as a rig interpolates between keyframes, and may not even show up under different circumstances, even those involving the same key poses. Hard to be certain, though. If the same thing starts showing up regularly, then yeah, maybe do include them.
Keep in mind that some parts of rigs do have “circular” motions they impart to the mesh, because the bones are rotating, pivoting. But this is very much the way the body moves as well, so using a linear correction (shape key) may not be as natural-looking as correcting the rotation at that point by adding an intermediate key. Highly flexed knees can be particularly prone to these kinds of small problems (they aren’t really errors, btw – the interpolation is correct for the keys you have), and kneeling can make them more frequent, because you essentially have two pivot points around which the knees can rotate – the feet/ankles, fixed to the floor, and the hips, possibly moving in a couple of axes. Think about performing a similar move yourself – as you lean forward from a kneeling position, weight is transferred to your knees. Physics keeps your knees from penetrating the floor, but not the knees in Blender! So you have to compensate for that. Same for many other situations that can arise when setting up a sequence using library poses. Armatures rarely move 100% naturally on their own – it’s the animator’s job to whip them in line!
