Mesh Armature elbow help needed

I’m looking for a tutorial or an explanation of how to set up a joint such as an elbow or knee so that I don’t get any pinching.

When I bend the arm 45 degrees or more, the elbow will pinch. Like bending a straw.

I thought the solution was to have a few edge loops with maybe one or two edgloops being shared VIA vertice groups by the two bones. In this gase the forearm and bicep bones. I’ve tried adjusting the weight of the vertices, but can’t seem to get the right combination.

http://s02.picshome.com/187/screen_shot001.jpg

http://s02.picshome.com/187/screen_shot002.jpg

I had a similiar problem when I first started designing characters.

(these solutions are NOT perfect but they will help you in the right direction.)

  1. creat a small (Very small) "elbow bone) no humans don’t have this however it will create a small space and limit the pinching.

  2. this hint is counterintuitive but goto edit mode and shrink the “elbow” area of the arm. joints are generally smaller. (I didn’t believe this at first but it is true).

  3. Shape the biceps and forarms. although this will not directly take care of the pinch it will make the arm look a LOT better. this said as long as it looks good it will pass.

hope this helps. I migth try to post some pics of my versions. Again this is not perfect but definetly a step in the right directions.

BlackManta :Z

I guess I should clarify, if you are trying to model a realistic figure then joint size varies. for example if the arm is turned sideways the joing actually might be bigger. but in your angle on your post the elbow is smaller.

If you want to make fun cartoon characters that will pass just shrink the elbow region down all around. (then do sub-surf and set smooth) you will like the results.

BlackManta :Z

BlackManta

Thanks. I was considering something like that but I think it could be done without the extra bone. Check out this avi regarding the stretch to constraint. http://download.blender.org/demo/movies/stretchto_demo.avi

From

http://www.blender.org/cms/Stretch_To_Constraint.483.0.html

There’s no extra bone except for the muscle bulge. Notice the elbow stays in place, no pinching. Unfortunately the link to the blend file is dead so I can’t get a working example.

In the meantime I’ll try your way of doing it.

http://blender.isoserv.com/uploads/stretchto_demo.blend

Toloban has some majic demos and tuts on this subject that go all the way back to 2.28. For 2.4 all that gerrymandering is obsolete as you can now add Shape Keys to the mesh and drive them with an IPO from the rig.

Regarding our previous discussions about the Floor Constraint look at (you may already have) Rob Backmans rig here:

http://rapidshare.de/files/8796819/RobsRig.blend.html

Unhide all the bones you find in Edit mode that are not there in Pose mode to better get the picture.

%<

I have considered trying not to use the third bone, but I found it was actually a nice thing to use for elbows…(some seens you would bend at the forarm and others (if you needed a longer forarm :wink: ) would be bent right after the upper arm.(I am sure there is a rule against this but it really is kind of a nice option) I guess it has to do with what your goal for the final outcome is. I know even the formal models at the blender websites page offers (its ike Keyro or something I can’t remember) but they use three bone arms.

BlackManta

Here is a sample file using ipo driven shape keys (rotate the calf bone up to 110° to see the effect):
example.zip

Here is a text describing the process (I am still learning): http://kokcito.tk/rvk/ipo.html.

Setting up a skin stretching and muscle simulation system with shape keys might not to be so easy. For that example I used four shape keys. At 60°, 75°, 90° and 110°, and had to learn to tweak all the curves, because otherwise the movement looked quirky and the keys were difficult to edit.

I also thought so. For limbs that twist and other parts like hips, the magic might not be as obsolete. Constraints are still useful (or a combination of constraints and RVKs). Actually, not only shape keys can be driven, but also bones parented to empties or whatever Ipo curve.

Black Manta

I’d like to see how you did your rig. Would you mind posting or emailing me a blend file of your elbow rig?

FLigh % Thanks for the links.

As to the stretch_to_demo, I guess it was just to show the stretching constraint. When I rotated the root bone, there are vertices that are not assigned to any groups which cause some strange effects.

5009 posts!!! Do you ever sleep? Did you get a prize at Elysiun for hitting 5K? :wink:

toloban

Your tutorials look great! I’ll try them out tomorrow. It’s 12:30 AM here and I’m too tired to think for now.

Yeah No problem I will grab a character out and send it to you.
Like I said it isn’t perfect but I was going for the “cartoon” look anyway.
Oh one more thing whne you import your bones and your mesh will not be parented. So if you have a character standing rigid you will have to do all the parenting by hand. ohterwise part of the leg will go with the arm. That is why it is alwasy a good idea to make a character in the “jumping Jack” position.

BlackManta :Z
I will send you a blend file when my computer stops rendering.

BlackManta - Looking forward to seeing your rig.

tolobán - Wow, I leraned a lot from you tutorial, I’m still working through it. My first time thropugh it I could not get the shape to change with the bone rotation but I’ll have more time this weekend to study it.

Fligh% It looks like toloban’s idea could be applied to the toes so that they don’t go through the floor. I’ll experiment with it later.

I was editing the mesh based on Toloban’s concept and I wasn’t able to get the proportional edit mechinism to work. Is this a bug or was it it designed that way or perhaps there’s anew button that needs to be clicked?

I’m usig CVS windows 11-24-05

From the release logs at blender.com:
http://www.blender.org/cms/Modifier_System.681.0.html

The Cage Mode (Fig. 3.6) button is used to apply the modifier to the editing cage, which gives more accurate display of the geometry of a mesh once a modifier has been applied. This displays vert/edge/face positions in their modified locations instead of their original positions. It should be noted, however, that transform operations still act on the original locations of the cage vertices and not on the displayed locations.

Also described here by a user.
http://www.blender.org/forum/viewtopic.php?t=7261

Sadly, that means we still can’t precisely manipulate vertices when editing meshes which are transformed by an armature modifier. I had never thought of using proportional editing, but I can confirm it doesn’t work.

I don’t think this discrepancy is so terrible, it is like getting used to manipulate things looking at a mirror. I will try to update the tutorial soon.

So this is not a bug, and being in the finished official release logs must mean we will not have a predictable modeling mode with the official release. :frowning:

:frowning:

Thanks.

I guess it’s just going through a learning curve on how to maipulate the mesh. Frustrating as it is it’s still better than before.