# Thread: First, Thank you for all the help? Now a few questions?

1. ## First, Thank you for all the help? Now a few questions?

1. What is the difference between extruding a bone and adding a bone from the same point?
Answer: I just added an armature and then E a bone, then added a bone. The extruded bone has a parent and the added bone does not. But they are still part of the same armature...

When you give the added bone a parent to bone, it will not be scaled when you move the parent bone, unlike the extruded bone which is scaled in the direction of the moved parent. The extruded bone is linked or in the chain?

2. Whats a vector pole? Are they used only in the armatures? Are they the top and bottom of the bones?

When I add a bone and press r to rotate it, it rotates in all directions? comparing it to rotating a mesh object which requires you to press r twice to get full freedom of rotation.

3. Why does it do that? Is that to maintain the poles? or what? its fun to watch though.

4. Are we still required to add an armature only from top view? I added one from front and the axis all pointed correctly is why I ask.

I was researching free information regarding armatures and ik solvers and this is one of the first urls listed:
harkyman
12-Sep-03, 05:36
You need to make an IK solver. There won't be one automatically (yet).

As for IK/IKA: IKA's were the name given to the old armature system. When someone talks about IKA's, it's sort of like they're talking about the 0.5 version of armatures. IK refers to Inverse Kinematics, the calculation of the position of bones in a chain dictated by the location of the endpoints. It differs from the other method of bone placement, Forward Kinematics (FK), in which each bone in a chain inherets its position from up the chain.

How to make an IK solver:

1. Have a chain of bones.

In purple edit mode (TAB):
2. Select the endpoint (not the root) of the last bone in the chain.
3. Snap the cursor to this point (Ctrl-S)
4. Extrude a new bone from this point (e-key)
5. Create a new bone at the cursor point. Name it chain.acc.

The extruded bone you made in 4 is now a part of the IK chain of bones from 1. It will be your IK solver. The bone that created in 5 is not linked to the other bones. It will be your controller (thus the .acc suffix that I use to mean "actuator").

In pose mode (blue edit mode, Ctrl-TAB):
6. Select the extruded bone.
7. Move the the constraint buttons (the chain links)
9. Choose IK Solver from the popup menu that appears
10. In the OB field that appears, type the name of your armature (case sensitive, and at this probably just "Armature")
11. In the BO field, type chain.acc

Select the chain.acc bone in pose mode, move it around and you should have working IK!

Good luck.
aersoy
12-Sep
yes I know its like four years old, but it helped a lot in my understanding, but as information does, it led to the questions above.

I just did this simple tut, and am ecstatic!,

LOL, I think I need a tut that starts:

Armatures are special little objects, used to deform a mesh. They are really fun to learn about and play with.

To begin, ........

2. Hello there weiry traverler.
I too am a noob at blender, but I have played around alot with the armature,

1, the difference between exruding and add a bone, is when you extrude you create a chain of bones, and when you add, you create a new bone, witch can become chains as well,
so it is just another option you have when creating the armature, and yes they are the same armature object. FYI you can have multipule armatures control the same mesh. and armature that control armatures also.
Verctor poles, from what I thought they were, are mostly found in sphears where all the verts merg into one, at the top and bottom. does that sound like it fits your idea of a vector pole?
As for rotating the bones, you can select(while in edit mode) the tip, or the base of a bone to re oriant its postition, or if you have the bone selected, it will rotate the entire bone.

here are a few pricless tuts on riging
http://wiki.blender.org/index.php/BS...cter_Animation
http://wiki.blender.org/index.php/BS...rmature_Object

And lets not for get the ever popular Ludwig, I learned so much from picking this guy apart, you can download the fully rigged character here
good luck and keep blending

3. 1) Both of you got it . When you extrude a bone you are extending the bone hierarchy . When you just add a bone it does not extend the hierarchy and the added bone is at the same hierarchy level as the first bone you added in that particular armature object . You can change this by going to the Armature Bones panel in edit mode and choosing an existing bone from the drop down menu next to the "Child of" or selecting a bone and Ctrl-P it like you would for any other parenting operation in bone edit mode .

2) Pole vector is actually a term used in Maya . It refers to the direction a bone is set to point towards in Maya rigging . For example, the direction you want the knees to point towards can be set using pole vectors . Apparently Blender will also get this feature soon . Right now you have to add target bones so that the knees will only bend one way (see Ryan Dale's BSoD tutorial), but with the option to use pole vectors you won't need to do this in the future .

When I add a bone and press r to rotate it, it rotates in all directions? comparing it to rotating a mesh object which requires you to press r twice to get full freedom of rotation.
Er... You must have pressed R twice because the trackball function is not automatic for bones either ...

3) So you have to understand that an armature bone on a programming level is in mathematical terms a vector (if you remember your math lessons a vector is simply a segment in space with with a starting point and end point with a particular direction) . So if you extend this to the armature bones the head of a bone is the starting point and the tip is the end with the direction of the bone going from head to tip .

4) Yes you should always add in top view . An armature bone always has its axes set (Y is always up X side to side and Z depth) and you cannot change this like you can with mesh objects, so it seemingly won't matter which view you add a bone while in Edit Mode but in Object Mode your armature object will have a 90 degree rotation around the X axis (if you add it in front view) which can and usually does create problems down the road .
If for some reason you want to add bones in front view simply start by adding the first armature bone in top view ad then switch to front view to add additonal bones . You can just delete the first bone or rotate it while in Edit Mode .

4. When I set the child of for a new add/bone it is still separate from the chain, meaning I can grab part of the chain and pull the rest, but the add/bone does not follow with them, and I cannot move the chain by moving the add/bone.

Nope, I pressed r once. I tried it several times thinking I was doing something wrong. The bone rotated the normal 90, etc, but also rolled. Not like the trackball type of rotation. Taking the bone tip pointing north, and rotate it to point west not by the tip but by selecting bone. As it moved, it was as if the back of the bone also rolled around to the front.

It was cool to watch. If you look at the pictures, you can see the black part of the bone (arrows pointing at it) shows how it is rolling while rotating it to the right.

Id guess it has something to do with the poles directions too.

I could take some pics and make a gif, but that doesnt show the that I pressed r only once, lol.

I dont recall taking any vector math. Maybe it was called something other than that? Hmmm.... now I am curious, I loved all math. Math is a game in itself.

So if I have time perhaps I will compile the new blender with the polls in it... sounds like fun.

Thank you

5. Wow, you know what? If you add the bone in top and then rotate it so it points up in front view, the stuff in the statement above works.

However if you add the bone in front view, and then rotate it? it rotates normally.

Heres the blend

6. Ok now I see what you are talking about ... you are rotating a bone in Edit Mode in the front view ... and yes all of that behavior does have a lot to do with vectors and the fact that armature bones have a set orientation ... and the fact that Blender's default views have the Z as the "up" axis while the armature system is coded with the Y as the "up" (like most 3D apps) ...

When you rotate a bone in the front view, when the bone is aligned to that view and the Z is the up axis, you will give a roll value the bone because it is rotating perpendicular to its coded up axis ... this can cause you problems in some situations when you want a "neutral" roll value in Pose Mode... in most cases you'll want to recalculate the roll value with Ctrl-N (which will remove the visible rotation and insert a value in the "Roll:" field in the Transform Properties subwindow) and give it a non zero roll value in Edit Mode so that in Pose Mode it is properly aligned and rotated for poses and constraints ...

You won't get that behavior if you rotate in either the top or side views if the bone is aligned to the view ...

7. Hmmm, lets see. So you can only rotate the armature bone in top or side view.

Seems very strange. Is that in the wiki someplace? LOL.

Anyway, thank you again. Im very glad Im not crazy, and my blender is not broken, nor my graphics card.

Another question:
if the bone is aligned to the view ...
What does that mean? you want me to stand up so you can throw something at me?

Ok did a fast search on vectors, vector graphics, and started reading, and I do remember working out those equations for curves etc, lol. But I still dont recall, poles and magnitude.

But Im tired. I just thought they were points. you know I really loved playing with that stuff, I wonder if I can find my college math books. I did run across a notebook full of notes. I couldnt understand the last half of it anymore...

8. Hmmm, lets see. So you can only rotate the armature bone in top or side view.
No you can rotate armature bones in any view . It's just that if you have the Y axis (the axis the bone rolls on) perpendicular to the Global Y axis then you will have to recalculate the the bone roll angles to get it aligned properly for pose space .

By "bone is aligned to the view" I mean what it is like when you first add a bone in a preset view, i.e. head at bottom and tip up at top in Edit Mode with no rotation applied .

And If you really are interested in learning about vectors as it relates to CGI just pick up a book on game programming . A good one will explain some of the math as it applies to the programming as well as some of the basics . It seems you can't do CG programming without using vectors ... and matrices ... both go into every aspect of CG from the rendering (realtime and "render" rendering) to the animation ...

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