[x3d-public] Feature comparison of glTF and X3D as Interchange Formats

[Michalis Kamburelis]

My intention was not that I want to compare specific X3D and glTF browsers.

I was pointing the fact that if the goal of the table is to help people in
choosing the format (X3D or glTF), then comparing "X3D Interchange profile"
vs "complete glTF specification" is not perfect. You choose a subset of X3D
specification (I think all X3D browsers implement something more than
Interchange), and compare it with the full glTF specification (that is
unlikely supported by most glTF readers).

I do not have a solution to this problem, I know that designing a "fair"

- subset of glTF and
- ‎superset of X3D Interchange

...would be hard (lot of work, hard to do it objectively, and outside of
what you wanted to describe).

I'm only pointing that the current table should not be used as a simple
guideline "what I can practically do with X3D vs glTF". And I fear it will
be taken as such -- the title of the page is "glTF/X3D Comparison", and the
fact that it's limited to X3D Interchange profile may be lost to some
people (or not understood, if someone is coming from outside of X3D
community and doesn't know that "Interchange profile" is a bare minimum in
practice).

I hope that this explains my intentions better.

As for the "runtime" -- I see that my understanding of this word was
different than yours, so please disregard my notes about them.

Regards,
Michalis

22.09.2017 4:46 AM "Leonard Daly" <Leonard.Daly at realism.com> napisał(a):

Michalis,

To compare X3D's runtime with glTF is not an appropriate comparison. It has
nothing to do with the heaviness or lightness of X3D's runtime, but the
fact that glTF does not have one.

If the work flow is to ingest models and make modifications, then the
runtime capabilities are irrelevant to the extent that those capabilities
do not impose requirements on the importing tool.

Since the addition of components of a profile is strictly a browser choice,
it does not have any place in a comparison of specifications. This
comparison was not to establish test cases for bench marking various
browser that support glTF or X3D (or both). This was strictly a comparison
of features that are in the specification.

If you want to see a comparison of browsers please feel free to go ahead
and design and do the testing. It is beyond my available time right now.


Leonard Daly




2017-09-21 23:40 GMT+02:00 Leonard Daly <Leonard.Daly at realism.com>
<Leonard.Daly at realism.com>:

Since higher level X3D
Profiles include a lot of run time and glTF does not include any, it would
not be a fair comparison -- it wouldn't even be relevant. Someone might need
to work in a specific environment which would preclude X3D's runtime.

But an X3D browser can implement the parts of X3D responsible for the
missing features (vs glTF, in your table) without "a lot of run time".
I know that it's more-or-less what I'm doing myself (details below).

If you consider some X3D browsers as "heavier" on resources than some
glTF browsers, then you should point and
compare these specific browsers, and mention that browser X (which
happens to use X3D) is heavier on resources than browser Y (which
happens to use glTF). As far as standards go, saying that X3D requires
"heavier runtime" for the same features is not true, in my experience.

I actually do implement in my X3D browser various features that you
list as missing in your table (since they are indeed missing from the
Interchange profile). I'm quite sure that implementing these features
does not make the runtime "heavy", at least not more than implementing
them using glTF would be.

Some details:

- Implementing [Indexed]QuadSet nodes (which is part of CAD component,
and provides "Quad surface model" feature in your table) is very easy,
and it does not require anything special from the runtime. It's just
another geometry node. (Some APIs, like OpenGLES, may not support
quads, but you don't pass polygons from IndexedFaceSet straight as
polygons to OpenGLES either.)

- Using shaders is something that all renderers do already, regardless
if it reads X3D or glTF. Exposing shaders to the X3D author is
relatively easy, and it does not require any "heavy runtime", you just
copy some data from X3D shader nodes to your renderer shaders.

- Implementing animations (using morph and joints) is indeed not
trivial (to do it efficient). But it's the same level of difficulty as
doing it with glTF.

- Implementing bump mapping etc. using X3D CommonSurfaceShader is the
same level of difficulty as implementing these features using glTF.
The input format doesn't really matter here much.

Regards,
Michalis



-- 
*Leonard Daly*
3D Systems & Cloud Consultant
LA ACM SIGGRAPH Chair
President, Daly Realism - *Creating the Future*
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://web3d.org/pipermail/x3d-public_web3d.org/attachments/20170922/5d60a553/attachment.html>