How I can avoid a model getting thinner with weighted bones?

[gedo831]

When I apply two bones to a mesh setting cp's bone weight and I bend or rotate one of the bones, the model getting thinner.

I am trying to use bone weight function to my model's joint like knees and elbows so I want it to keep the same thickness.

I know I can do it using fan bones with constraints, but I want to do it with bone weight because I want use my model in my 3D games and so I want my models to be simple as much as possible.

Does anyone can advise me how I avoid my model getting thinner with bone weights?

 

Thanks,

[itsjustme]

When I apply two bones to a mesh setting cp's bone weight and I bend or rotate one of the bones, the model getting thinner.

I am trying to use bone weight function to my model's joint like knees and elbows so I want it to keep the same thickness.

I know I can do it using fan bones with constraints, but I want to do it with bone weight because I want use my model in my 3D games and so I want my models to be simple as much as possible.

Does anyone can advise me how I avoid my model getting thinner with bone weights?

 

Thanks,

 

Okay, first, if you twist anything like that, it will get thinner, gedo831. In that image, you are rotating the bone on its' 'Z' axis, so, that's what will happen. An arm or leg would rotate either on the 'X' or 'Y' axis depending on how you set it up, but the 'Z' axis will always cause a loss in volume when done the way you have your example...it wouldn't if the bone were turned sideways and positioned at the knee, but that's not what you have.

 

Next, you've got a lot of Control Points for a knee or elbow there. For every joint, make sure you have three spline rings and at least one spline ring between each joint. This image of Squetchy Sam's arm should illustrate what I mean...you could put more if necessary, but that amount of spline rings can do the job. Sam can be downloaded using the link in my signature at the bottom of this post.

 

Lastly, if you do run into problems with losing volume on a limb when bending, you can use different CP Weighting, fan bones, more splines or Smartskin to correct it.

 

Hope that helps.

[gedo831]

itsjustme,

 

Thank you for your advise.

Your lecture is filled with good explanation. Now I completely understand how AM's bone&cp weight behaves and I need to do some trick to use a model for my 3D games when I get it exported from AM.

Thank you very much!

 

gedo831