beginner bones/skinning problem

[Anonymous]

Salutations,

I am having a beginner's problem with applying Skin with bones in 3ds max 8.
I will try to describe the problem: imagine an animal with a thick neck, like a horse;
now, imagine putting bones and Skin in the head of this horse. Here is the problem:
since the neck is thick, where am I supposed to position the bone inside the neck?
If I put it very high (closer to the spine) and skin it, then turning the horse's head upward
will work fine, but rotating it down will make the lower part of the neck enter in the body,
since all vertices of the neck need to have weight in the Skin. Now, if I position the neck's bone
lower, the same problem will happen. See the problem? I don't know if it is very clear.
(Note: Envelopes don't work for us; we prefer changing the weight of each vertex individually.)
Anyone has a workaround for this problem? Free tutorials are extremely difficult to find.

Thank you in advance.

[Anonymous]

I would put it in the middle, with a slight bias towards the real spine location... realize that you can move the ends of the envelopes if they are not influencing the whole neck in section. BTW - I hardly ever have to weight anything but a few stray verts... post a screen dumb if you continue to have problems.

-Shea

[Anonymous]

Thank you for your patience.
We actually have not very much practice in skinning. We are beginners.
As we are not sure about how to proceed, we attached a screen dump as
you suggested.
Note: actually, the horse is just one case. This same thing naturally
happens with bending arms too.
Note: we are from Brazil, so our English may not be very expressive.

[Anonymous]

Your model is pretty sparse along the neck, a few extra edge loops should help take the linear segments out when it is deformed. The trick is in blending the envelopes, with some overlap such abrupt changes during deformation can be eliminated... in this case bones representing the spine along the back would be used to blend between the areas that you are currently having trouble with. Even if you only need to animate the neck and head (judging form the lack of bones), you can still put some additional bones in there to blend with. This is the beauty of envelopes, they weight the verticies based on falloff, not hard values. Enable the falloff shading to really see your work,.. a nice gradient of colors shows nice falloff between envelopes.

BTW - Are you using smooth instead of mesh or turbosmooth? You know it is for smoothing across faces and not for subdivision to increase the model's resolution... a common workflow.

Your english is fine, charming even. I look forward to your progress!

-Shea

[samab]

This is just to illustrate what Shea said about blending. The red verticies have 100% weight, they will be influenced by that one bone only, that is what is causing the bad creases, not the position of the bone. That's OK for those in the middle on the neck, but verts on joints need to be blended with adjoining bones for smooth deformation. Your horse needs at least a backbone for the base of the neck to blend with and the top of the neck must blend with the head.
The orange and yellow verts have partial weight and blue have low weight.

[Anonymous]

thank you for the responses.
we understood what you meant. we tried applying it and the
movement of the head now seems fine, but there is still some
problem with the movement of the neck. look the attachment.
we want the head to be able to lower, so that it reaches the
ground (for grazing).
actually, we are still going to add more bones, but we started by
the head/neck because we already knew it was going to give problem.
note: this horse model is not ours. we are using it for learning
purposes; we are learning it by ourselves.
obs.: just a thought, but maybe this horse model is not ideal for
skinning, because of the way faces are organized?

[samab]

It's best to make all your bones before skinning, though you can add more later if need be. It would help to divide the neck into more bones, that way the first link does not have to rotate as far and make a big crease (see pics).
Get some refernce images of horses grazing to see how they move. There are some links to horse anatomy/skeleton reference on this link I saw on another thread, it may be helpful for you.
http://forums.cgsociety.org/showthread.php?f=202&t=257570

[Anonymous]

Salutations,

Thank you for the answers. We really didn't know this envelopes'
falloff technique. It is very good. Thank you also for the horse
pictures and references.
We put more bones in the neck.
The horse's neck now bends fine, we think, but it is strange, the
initial size of the neck + head of this horse seems too small for
being able to lower and reach the ground.
How can this horse's head reach the ground? Does he stretch the neck
in some way? It seems that the neck is longer when it is in
grazing position.

Thank you in advance.

[samab]

I'm not really an equine expert, but looking at the reference pictures, the horses neck and head in the up position have a slight S shape curve. in the down grazing position it appears to be straightened out. This would account for the increased length.
Lots of reference images:-
http://images.google.co.uk/images?hl=en&q=horse+skeleton&btnG=Search+Images&gbv=2

http://images.google.co.uk/images?gbv=2&hl=en&safe=off&q=horse+grazing&btnG=Search+Images