[x3d-public] X3D Model Archive Format

[Leonard Daly]

I just wrote a post about using X3D as a Standardized Model Archive 
format. The article is at 
http://realism.com/blog/model-archive-format-x3d. This message 
summarizes and quotes portions of it for discussion.

I mentioned a number of formats include FBX, OBJ, glTF, and X3D as 
possible candidates for an archive format. X3D is the only one that is 
ISO standardized. Vince has pointed out that glTF is not an archive 
format in that the file contains data in a format that allows it to get 
into the GPU with minimal processing".

"It is important that models exist to be imported into a scene (or 
sub-scene). The models may contain animation, but this key-frame 
animation that indicates what part of the model needs to be where at 
various relative time values. Models do not contain a run-time or 
interactive component. Neither do they contain lighting or environmental 
effects (backgrounds, fog, etc.). These features are added in the scene 
rather than to the model."

*Current ***Industry *Work Flow*

"The current state of modeling creates a quad-mesh as the surface 
geometry of the object. The model is animated either as multiple meshes 
(rigid body animation) or (much more frequently) as skin deformations 
due to joint movement. Faces or other highly deformable surface with a 
fixed underlying structure are animated as morphs using morph targets. 
[The target is a linear combination of a basis set and the animation is 
the path to get from existing to target.] Textures are created and 
applied to the model. "

A note on animation: FBX has established the standard (by use) of a 
single master timeline for all animations. Individual animations may 
occupy just a portion of that timeline.

*Model Profile Requirements*

A Model Profile needs to provide archive support for all of the ways 
people model, texture and other appearance, and animate.

* 3D geometry capabilities
  - Triangles
  - Quads
  - CAD (NURBS, CAD structures)

* Appearance capabilities
  - Image texture
  - Advanced texturing (bump, emmisive, occlusion, etc.)

  * Animation capabilities
  - Single timeline
  - Skin/joint motion
  - Morphing & Morph targets

I believe that most of this is easy to accomplish with material in V3.3. 
The new/revised capabilities could be added for V4.0. In conjunction 
with the definition, a 2-way conversion library should be provided. 
Inbound would be calls to create the appropriate X3D data structure. 
Outbound would handle things like triangulation. It might also be good 
to have a single file format where the X3D and external media files are 
zipped/merged together.

-- 
*Leonard Daly*
3D Systems & Cloud Consultant
LA ACM SIGGRAPH Chair
President, Daly Realism - /Creating the Future/
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