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View Full Version : Why do they call them Skinned meshes?



WhatEver
10-19-2002, 03:38 PM
I've seen in several places where they call deformable meshes skinned meshes. Are they not the same?

Hmmmmm, this doesn't seem OpenGL related. I'll make it OpenGL related http://www.opengl.org/discussion_boards/ubb/smile.gif.

Could you point me to a link that does skinned meshes with vertex programs(I already know of one, I just want to make this thread OpenGL related http://www.opengl.org/discussion_boards/ubb/biggrin.gif).

dorbie
10-19-2002, 05:10 PM
AKAIK skinned meshes are simply meshes that deform based on seletal keyframes. So under the mesh there's a simple stick model that is animated with keyframes. That is interpolated and the mesh is deformed based on the 'bone' it is attached to, or some weighted interpolation in an intermediate zone near a joint for example.

jwatte
10-19-2002, 05:33 PM
It's called a "skinned" mesh because it's a surface "skin" that's clad on top of a stick figure "skeleton". Vertices are attached to one or more skeleton bones with weights for each important bone.

When you say "deformable mesh" it's a bit less well defined. For example, if you store morph target meshes and interpolate with weights between source mesh and target mesh, that's a "deformable mesh" but it's not (necessarily) a "skinned mesh".

WhatEver
10-19-2002, 08:11 PM
Ok, I can see how saying deformable mesh would be to broad of a term. Saying skinned doesn't really work either though. Skinned is a term already taken for the texture mapped onto a mesh, so that's why I think it's a bad choice of words. Instead of skinned mesh, maybe it could be called skinned bone or skinned joint.

I guess there really isn't a short way of saying: Deformable meshes infuenced by a hierarchy skeleton http://www.opengl.org/discussion_boards/ubb/smile.gif.

Korval
10-19-2002, 10:08 PM
Skinned is a term already taken for the texture mapped onto a mesh, so that's why I think it's a bad choice of words.

No, skinning has never been an accepted alternative for texture mapping. The mod community has stolen and damaged this term, using it instead as a shorthand for applying texture maps to a character.

The use of skinning for skeletal models/animations makes perfect sense. The use of "skinning" makes little sense in terms of applying texture maps, especially since textures (especially Quake model textures) have little to do with skin.

The only way I would accept "skinning" as some form of texture mapping is if you're doing that nifty stuff they did in Shrek to make skin. Their multilayered texturing could be considered "skinning", not basic single-texture mapping of clothing.


Instead of skinned mesh, maybe it could be called skinned bone or skinned joint.

Neither of those terms makes any sense, given the accepted meaning of "bone" and "joint". Skinning a bone (where bone means transformation matrix) doesn't make sense. And "skinned joint" makes it sound like you're only doing the skinning at that location.

WhatEver
10-20-2002, 07:49 AM
The use of "skinning" makes little sense in terms of applying texture maps

I was going to disagree 100% with you until I realized that the term "skinned" makes sense when you're refering to a skeleton or a mesh.

Think of a house without panels nailed to the vertical wall supports yet. That's called a skeleton. The panels are the skin. So in your case the term "skinning" applies well to this situation.

Now think of a wire mesh in the shape of whatever you want. You can cover the mesh with paper, and that's considered skinning.

The definition of "skin": A usually thin, closely adhering outer layer

So the term skin can be used either way.

It makes sense to me now why they would call it skinning when referring to a skeleton.

jwatte
10-20-2002, 10:04 AM
I agree it is confusing because "skinning" in vernacular means just any kind of customization of how something looks. I e the mod community stole "skinning" of something like WinAMP to mean "skinning" of an existing mesh by swapping out its texture.

However, for the last 15 years or so, "skinning" in computer graphics has meant putting a deformable mesh with bone-weighted vertices on top of a (typically hierarchical) skeleton of "bones" (transformation matrices). CG was first; that's the definition I'll stick to :-)

V-man
10-20-2002, 10:35 AM
I thought it was official to call texture mapping ->skinning. It is so common nowadays that even popular applications like winamp, netscape, etc call it skinning. It's better to call those themes.

Texture mapping can be called texturing, plain and simple.

V-man