From Metaverse U Wiki
Streaming Collada Graphics and physics content for use in a virtual world
Theo Armour:
I want to get the next autocad to go into virtual worlds:
- Collada is a database format
- Something like an autocad model (eventually tool) into a virtual world
- Architect edits model, architect saves into the virtual world
- others view it... he changes things and the model is updated quickly
- Audience sees the update (those who oversee the look&feel of model)
- Medical imaging with model synced via collada
Daniel Miller
- Advantage of open source project:
- If architected well, modular and usable
Theo Armour:
- Cannot use something that needs a translation
Daniel Miller:
- RealXtend modules actually let you import ogre meshes
- Ogre meshes are convertable from collada
Theo Armour:
- Need to accurately represent models for visualization with low
turnaround time
- Needs to have immediate feedback from user/viewer and quick turnaround
Daniel Miller - Collada Question:
- Difficult without validation + tests
- What does 'friction' mean: it's even dependent on physics engine
+ timestep
- Maybe specify
- Worry: not concerned about meaning of the parameters
-Daniel Horn
- Physics format looks like:
<physics_material id="RigidBody1-material" name="RigidBody1-material">
<technique_common>
<dynamic_friction>0.200000</dynamic_friction>
<restitution>0.600000</restitution>
<static_friction>0.200000</static_friction>
</technique_common>
</physics_material>
- Daniel Miller
- Who decides what it means with dynamic_friction
- In MPEG days we went down to the pixel
- Daniel Horn
- I don't think you could make people adopt your standard if you
specified exactly how the physics converge
- You could make a special phyics technique for your physics engine
that had your specific need
- Daniel Miller
- So then basically we're agreeing on a way to misunderstand each other
- We have separated with syntactic vs semantic information
- We've basically only agreed on getting the structure of the data
from machine A to machine B
- Daniel Horn
- You could disallow certain optimizations by specifying exactly how
physics performs
- Theo Armor
- You can live with decisions made years ago if you make a brittle spec
- If you can get collada and learn to deal with it you're set for a
few years
-
- Depends on What you want to do: if it's a very specific scientific model
- Depends on the application
- Theo Armor
- Can you load part of the model: and just be able to look at the
relevant portion of the geometry
-Daniel Horn
- There's a way to stream collada, so maybe you can skip in the stream
-Daniel Miller
- O3d was nice with that streamable .tar.gz format so you can get
callbacks at each file
-Daniel Horn
- There was a zipped dae specification so you can download the zip
of the collada to get the compression
- Ryan
- Collada DOM + C code to parse it
- Jukka Jylänki
- To get second life to do medical work would be a huge engineering
- effort
- Theo
- The virtual world for the time being is probably just best for viewing
-Daniel Miller
- That kind of physics has different codes for different specializations
- You'll not get a godlike physics engine that will work for
different domains for the foreseeable future
-Ryan
- Is all the semantic information able to be stored within a COLLADA file
-Theo
- most autocad items are in 2d
-Daniel Horn
- It seems like you could jam 2d vector art into a file
-Theo
- The difference is that the viewing conditions need to be different
---Back to worry about loose specifications within collada---
-Daniel Horn
- The whitepaper http://delivery.acm.org/10.1145/1230000/1229407/p101-coumans.pdf?key1=1229407&key2=1148173421&coll=GUIDE&dl=GUIDE&CFID=37151037&CFTOKEN=94708571
- big section on constraints
- Section that says: In addition to the mass and inertia of the object, the frictional and
elastic material properties are included. This provides enough
information for the physics engine to determine how the object will
react to the various forces and collision events in the environment,
using classical Newtonian physics.
-Daniel Miller
- Whatever erwin decided to call the collada fields will map nicely
to bullet
- So I guess since he got first dibs on the format, he gets the easy job
-Daniel Horn
- It may be easier to get collada working than custom formats we
invent even for a preliminary release of sirikata
-Daniel Miller
- I managed to do opensim: second life without a file format, but it
was a kludge
- If there are standard C++ libraries we can link in
-Daniel Horn
- I'm pretty sure that the programs are importing/exporting collada
-Daniel Miller
- I'm wondering if there is simple example code to import port
- Jukka
- I'm pretty sure the collada.org has collada import, and probably
in bullet itself
-Daniel Horn
- How should we reconcile that our systems want to store their
external assets by their hash but collada lets you store your items
by any old URI
- Jukka
- I don't think that users are going to make the same texture name
without the same URI
- Daniel Horn
-I want to copy your mesh and store it at my URI but have the same
fingerprint so that my caching system only downloads it once
-I'd like to encourage baking the fingerprint into the URI
- Jukka
- That's a security issue...
-Daniel Horn
- You can verify if the hash when you donwload it
- But how can we encourage our URIs to be saved by hash
- Jukka
- As soon as you get a collision you have a security problem (cache pollution)
- Daniel Miller
- Collada isn't exactly compact
-Ryan
- They said you should zip up the collada file
- Daniel Miller
- Maybe collada should be considered only an authoring format
- What's our path should be for getting them into binary
- Are we going to cache parts of the mesh so that we can obtain
parts of it?
-Daniel Horn
- Remi and co said that collada is only an authoring format but you
should convert to your binary format before giving it away
-Daniel Miller
- It would be nice to tune your compression to the XML itself
So that you can save your files for years
- Maybe you can use an ephemeral compression format tuned to the
streaming itself (eg wire protocol) but keep the asset as XML
-Daniel Horn
-But if you want to use an existing CDN system you can't have
serverside compression logic--and you store what you eat
-Daniel Miller
- So what if you want to just download the physics part to part of
the system and the graphics for the other part
-Daniel Horn
- You could store separate COLLADA portions for physics and
-Bonnie Devarco MediaX Stanford:
- I'm here for a virtual world purpose
- I represent an education community who have abandoned worlds or
resuce universes
- All of these object sets are in .rwx renderware format
- We created our objects using 3dstudio max or notepad and they've
been translated
- We own our object sets but not the world format (aw is still alive
after 10 years) but they never took off like second life (pre-broadband)
- So we don't want to lose that work
- Now we have our ephemeral worlds and we can't use the modules yet
with collada
-Daniel Horn
- I think that you could hire a programmer with marginal knowledge
to write a converter to collada
-Bonnie
- Would you want to convert directly to Sirikata?
-Daniel Horn
-I would suggest you converted to the collada interchange format
first then figure out how to convert that to ogre or whatever
world format you would use
-Bonnie
- Ya because our worlds are still usable and very well done and we
want to convert those to 3d worlds
-Jukka
- All your objects are in renderware? Can you convert them and
loadable somewhere?
-Daniel Horn
- You can potentially capture the actual buffers from the graphics
card and export those to collada
-Bonnie
- We can still run it on the closed source worlds
-Daniel Horn
- Since it's a closed source world you could get coders to sit
between the graphics driver and the code to capture the meshes and
save them into collada
-Daniel Miller
- Is the company still alive?
-Bonnie
- The new company bought the world but does not have a license to
run it
-Daniel Miller
- Maybe you can hire a contractor to pay to convert the format into
collada cus they have the core knowledge to do this
- $10,000 can get them to jump through hoops
-Jukka
- You might be able to go directly to criterion or EA to help them
-Daniel Miller
- Activeware may want to make happy customer
- Jukka
- Maybe you can go get a trial engine for renderware and then write
a simple code to export it using their engine itself (rwx is not
dying, so it will stay alive even if activeworlds is alive)
- Actiev worlds may still have some extensions
-Bonnie
- Community built activeworlds is still alive
- We were waiting for a new open source opportunity to come along
