[Gdal-dev] Autodesk DWF library

[Andy Canfield]

I have much interest in this area/topic as it is a part of my everyday work. I 
have worked a little with DWF, a lot with dwg, and a very little with DXF. 
Here is some background on where I have been with this issue so far.

There is more than one dwf format. There is the old Whip compatible format and 
there is the new format which is what that download deals with. 

The new format is a lot more complex than the old one but does a lot more cool 
stuff. It is still however basically a raster format with very little entity 
information other than what is visually displayed. The new format works a lot 
like a jar file with a manifest and uses the same compression as zip and jar 
files. 

As far as dwg goes there are right around 6 dwg formats and they are not in 
any usable way compatible with each other. They are the Pre-R12, R12, R14, 
2000, 2000i-2002, 2003-2006 formats. Autodesk will not release any stand 
alone libraries to deal with any of the dwg formats unless you pay for it. I 
work for a huge corporation and we have asked more than once and the answer 
was an absolute no. The format 2003-2006 is also encrypted or as AutoDesk 
says "locked to validate data". 

OpenDesign formerly OpenDwg is free for in house use but you must pay if you 
distribute for money. I think if you keep it open source and don't charge for 
it it is free as well(I would have to check on that though). Their API 
follows AutoDesk's ObjectArx and ObjectDbx API's so closely that the function 
signatures in their libraries can in many cases be extracted and compared and 
there is no binary difference between the stubs. This makes OpenDesign really 
easy to use if you are familiar with ObjectArx because where they lack 
documentation you can guess and pretty sure you will be correct. The nice 
thing about OpenDesign is that it can be used on other platforms besides 
Windows. It supports all the dwg formats and all the dxf formats. They also 
have an OpenDgn library that will support the Microstation dgn's and Bentley 
uses the OpenDesign stuff for their dwg to dgn translator so their support 
for dgn is good as well. Though not as well documented as their dwg/dxf 
library.

I have had some discussions with people, Frank included, about supporting dwg 
in gdal/ogr and it basically comes down to if you want good support for dwg 
without going through AutoDesk you have to use OpenDwg. If you put that in 
there then you would have to do it as a conditional support so if the user 
doesn't want to negotiate an agreement with the OpenDesign alliance they can 
choose not to. After that it amounts to is there enough demand for it and who 
is going to spend the time implementing it? 

I currently use the OpenDesign libraries and the Ogr source in the same 
application so I know there is no compatibility issues between Ogr and 
OpenDesign anyway. If somebody volunteers to implement this I am more than 
willing to help out with any questions they might have about the OpenDesign 
C++ API's. 
Thanks,
Andy

As an aside:
My approach at my work so far has been mostly readers that translate the 
OpenDesign objects to Ogr objects( overloading operator= ) so they can be 
displayed by my apps with one draw function vice a bunch of special cases. 
The areas I have been running into headaches with is the 3D nature of dwg 
objects and some of the odd things they support like bulges in polylines 
where the bulge can jump out into the Z which doesn't display well in 2d. So 
if anyone has ideas on how to make this look decent in 2d please let me know.


On Tuesday 12 July 2005 17:21, Paul Selormey wrote:
> It is simply an alternative to PDF. It started as Whip (may be
> to whip PDF!).
>
> If there should be a support for Autodesk formats, obviously it
> should be DXF and DWG. May be one day Autodesk will sponsor GDAL
> to add the support for their RealDWG library.
>
> Best regards,
> Paul.
>
> > -----Original Message-----
> > From: gdal-dev-bounces at xserve.flids.com
> > [mailto:gdal-dev-bounces at xserve.flids.com] On Behalf Of Frank
> > Warmerdam
> > Sent: Wednesday, July 13, 2005 3:54 AM
> > To: Kralidis,Tom [Burlington]
> > Cc: gdal-dev at xserve.flids.com
> > Subject: Re: [Gdal-dev] Autodesk DWF library
> >
> > On 7/10/05, Kralidis,Tom [Burlington] <Tom.Kralidis at ec.gc.ca> wrote:
> > > FYI -- wonder if this would be useful for inclusion as an OGR
> > > supported format?
> > >
> > > ..Tom
> > >
> > > http://usa.autodesk.com/adsk/servlet/item?siteID=123112&id=5520675
> >
> > Tom,
> >
> > What isn't clear to me is how much interest there is in DWF support.
> > Reading over the DWF FAQ I am concerned that it isn't a very
> > accurate format.  I also *suspect* the original data is
> > pretty dumbed down for display purposes though I don't know
> > that for a fact.
> >
> > Best regards,
> > --
> > ---------------------------------------+----------------------
> > ----------
> > ---------------------------------------+------
> > I set the clouds in motion - turn up   | Frank Warmerdam,
> > warmerdam at pobox.com
> > light and sound - activate the windows | http://pobox.com/~warmerdam
> > and watch the world go round - Rush    | Geospatial
> > Programmer for Rent
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