Through the Interface

Getting to know the Project Draw API

Last week David Falck, over at the Autodesk Labs team, provided me with an API key to have a play with the API to Project Draw. This post documents what I did, and how it all worked.

Note: I'm not actually doing any coding whatsoever in this post: I used the handy API test page provided by the Autodesk Labs team, and so didn't need to write a single line of code.

So, first of all, you'll need an API key. Here's the one I got from the Draw team:

th1SIsnOTreAlLyMyapIkeyOfCourSE

Just kidding. I've changed the above key for the purpose of this post: if you want a key, get your own. :-P

Seriously, though: just email labs.draw@autodesk.com, and they will generate and send you your very own key.

OK, once you have a key, you can navigate to the test page and start playing around. I started by copying my key (the real one, of course) into the startSession test rig, and I then hit Initiate:

The Project Draw API is exposed via REST, as opposed to SOAP (another popular - if more heavyweight, from a client perspective - mechanism for exposing Web Services), which means you pass everything the service needs to identify the session etc., in each call made to Project Draw. So you will need to use your API key along with the session ID provided in the response received for the API call we just made for each further use of the Project Draw API.

The other way to start a Project Draw session is via the setXML web method, but we'll come to that later. For now we don't have any XML to provide, so we're going to open the blank session and create some geometry from scratch.

Copy the URL provided in the response to your clipboard and paste it into a new browser window. You should get a nice, new Project Draw page upon which to draw some geometry:

I drew some simple geometry using the Project Draw interface and saved it using File -> Save. This is an important step: if you don't save to the server, then clearly any calls to access the session's geometry via the Web Service will not retrieve anything very interesting.

Here's my model - please note that I just threw some filled objects onto the canvas, and had no intention of drawing a symbol with religious or nationalistic overtones (there's something vaguely masonic about the image, I have to admit, but it's nothing I drew consciously, honestly... which should be obvious from the colours I used, if nothing else :-)

Once we've saved our geometry, we can head back to the API test page and see what we can do with it.

Firstly, we can retrieve the XML representation of this geometry, by calling the getXML web method:

You can copy & paste the returned XML fragment into a text file, if you wish. The XML returned for my feeble artistic efforts can be accessed here.

Secondly, we can retrieve a rasterized view of our design, in PNG format:

This provides us with a nice, high-quality raster of our design:

Now that we've extracted our XML content and generated a pretty image from it, we can (and indeed must) delete the session:

Now that we have some XML content - which we could have generated/transformed/manipulated programmatically in some way - we can use it to create a new session, via the setXML web method:

That's it for today's quick tour of the Project Draw API. As you should be able to see from this procedure - and from the XML representation of the design I created - it's altogether possible to populate and manipulate content in the Project Draw service programmatically, and - as the API is simply HTTP - you're able to do so from the programming language of your choice (something we did not touch on at all today).

A final, quick note: if there's something more you'd like to see exposed in the Project Draw API, don't be shy - let us know. The Autodesk Labs team is really keen to get external feedback on this technology.

Looking for API developers to work with Project Draw

Over on It's Alive in the Lab, Scott Sheppard is looking for developers interested in working with the API to Project Draw. If you're interested, send an email.

Using AJAX to generate pages hosting Freewheel views

I touched on this subject a few weeks ago in part 2 of my DWF-related AU handout, but thought I'd come back and describe in more depth some of the fun (although a more accurate word might be "difficulty" :-) I had solving this problem.

I've been playing around with web services and XML since SaaS was still known as ASP, and have tried to stay up-to-date with the technology as best I can. I'm really a client-side programmer, all things considered: I've created some server-side code, but have mostly involved myself with desktop-oriented programming and creation of samples that developers can execute locally, rather than having to set up a host environment.

So when working with web services, I really want to provide a simple application that can be run locally and connects to these services via simple, understandable client code.

The problem I wanted to solve with my AU demo was fairly simple (at least so I thought): for a particular DWF file I wanted to create a page linking to - and embedding - Freewheel views of the DWF's various sheets. The logical way to do this was to use the DWFRender web service to query the number of sheets contained in the DWF, and then create a page using DHTML that had some content for each of these sheets.

The logic seemed sound, and I created a nice prototype with hardcoded sections for the two sheets of my DWF file. Here's the HTML code:

<html>

  <!-- saved from url=(0017)http://localhost/ -->

  <head>

    <title>Freewheel</title>

    <style>

      legend      { font-size: 10pt;

                    font-family: Calibri, Arial;

                    color: black; }

      button      { font-size: 10pt; }

      input      { font-size: 10pt;

                    font-family: Calibri, Arial; }

    </style>

  </head>

  <body bgcolor="#E6E6E6">

    <table width="620">

      <tr>

        <td>

          <fieldset>

            <legend>Sheet 1</legend>

            <table>

              <tr>

                <td valign="middle">

                  <fieldset>

                    <legend>Clickable Thumbnail</legend>

                    <a

                      href="http://freewheel.labs.autodesk.com/dwf.aspx?sec=1&dwf=http://through-the-interface.typepad.com/presentations/DWF/solids.dwf"

                      target="New"

                    >

                      <img

                        frameborder="0"

                        height="150"

                        width="200"

                        scrolling="no"

                        src="http://freewheel.labs.autodesk.com/dwfImage.aspx?page=1&width=200&height=150&path=http://through-the-interface.typepad.com/presentations/DWF/solids.dwf" /

                      >

                    </a>

                  </fieldset>';

                </td>

                <td>

                  <iframe

                    frameborder="0"

                    height="300"

                    width="400"

                    scrolling="no"

                    src="http://freewheel.labs.autodesk.com/dwf.aspx?sec=1&dwf=http://through-the-interface.typepad.com/presentations/DWF/solids.dwf">

                  </iframe>

                </td>

              </tr>

            </table>

          </fieldset>

        </td>

      </tr>

    <table>

    <table width="620">

      <tr>

        <td>

          <fieldset>

            <legend>Sheet 2</legend>

            <table>

              <tr>

                <td valign="middle">

                  <fieldset>

                    <legend>Clickable Thumbnail</legend>

                    <a

                      href="http://freewheel.labs.autodesk.com/dwf.aspx?sec=2&dwf=http://through-the-interface.typepad.com/presentations/DWF/solids.dwf"

                      target="New"

                    >

                      <img

                        frameborder="0"

                        height="150"

                        width="200"

                        scrolling="no"

                        src="http://freewheel.labs.autodesk.com/dwfImage.aspx?page=2&width=200&height=150&path=http://through-the-interface.typepad.com/presentations/DWF/solids.dwf"/>

                    </a>

                  </fieldset>';

                </td>

                <td>

                  <iframe

                    frameborder="0"

                    height="300"

                    width="400"

                    scrolling="no"

                    src="http://freewheel.labs.autodesk.com/dwf.aspx?sec=2&dwf=http://through-the-interface.typepad.com/presentations/DWF/solids.dwf">

                  </iframe>

                </td>

              </tr>

            </table>

          </fieldset>

        </td>

      </tr>

    <table>

  </body>

</html>

And here's what it looked like when displayed:

So far, so good.

To generate the DHTML code for each of the sections, which could then be called in a loop once we knew the number of sheets, was also pretty straightforward:

var freewheel =

  'http://freewheel.labs.autodesk.com';

function createViews(sheets)

{

  var container = document.getElementById('views');

  var htm = '<table width="620"><tr><td>';

  for(i=1; i<= sheets; i++)

  {

    htm += '<fieldset><legend>Sheet ' + i + '</legend>'

    htm += '<table><tr><td valign="middle">';

    htm += '<fieldset><legend>Clickable Thumbnail</legend>'

    htm += '<a href="' + freewheel + '/dwf.aspx?'

    htm += 'sec=' + i + '&dwf=' + path + '" target="New">';

    htm += '<img frameborder="0" height="150" ';

    htm += 'width="200" scrolling="no" src="' + freewheel;

    htm += '/dwfImage.aspx?page=' + i + '&';

    htm += 'width=200&height=150&path=' + path + '"/>'

    htm += '</a></fieldset>';

    htm += '</td><td>';

    htm += '<iframe frameborder="0" height="300" ';

    htm += 'width="400" scrolling="no" src="' + freewheel;

    htm += '/dwf.aspx?sec=' + i + '&dwf=' + path + '">';

    htm += '</iframe>';

    htm += '</td></tr>';

    htm += '</table></fieldset>';

  }

  htm += '</td></tr><table>';

  container.innerHTML = htm;

}

The only challenge remaining was to call our DWFRender web service from out JavaScript code.

Back in the old days I used a component from Microsoft to call web services from HTML & JavaScript, called the Web Service Behavior, or webservice.htc. This seemed to work fine, but is no longer supported, so I thought I'd find a more modern approach, something from the AJAX bandwagon, perhaps. AJAX is "Asynchronous JavaScript and XML", and is the latest & greatest technology for developing smart yet thin applications. Or so the buzz goes.

After searching around a while, I ended up trying a couple of approaches. The first was based a technique provided by IBM. It took me a while to get the code to run, and even then it wasn't getting the result I wanted. So I implemented another approach using a technique shown at The Code Project.

Once again it didn't return anything helpful, but then I noticed this statement on the page:

Please note that many browsers do not allow cross-domain calls for security reasons.

I researched this for some time, and realised that my JavaScript code was hitting a browser security problem. It seems that cross-domain SOAP requests are an issue: if your web-page is considered to be in one domain, it will not call out across to a web service hosted on another domain. Even the Web Service Behavior I'd used in the past didn't solve the problem (thinking back I'd been calling web services hosted in the same domain, so it hadn't been an issue I'd come across).

The security problem is actually with the XMLHTTP component, which is at the core of AJAX and is now implemented by various (probably all, but I'm no expert) browsers.

There are a few ways around this limitation: it seems that most commonly developers implement server-based code that calls across to the problematic domain, basically provided a local cache of the results. In terms of clarifying the problem and spelling out the alternatives, I found this site extremely helpful, as well as this follow-up post.

Anyway, it turns out that for the purposes of my demo I could cobble something that worked together based on fairly simply client-side code. I didn't go to the effort of implementing a cross-browser solution, as the main purpose is to demonstrate calling the Freewheel web service and not to solve the problem of World (well, Internet) Peace.

There were two points that I hadn't realised were issues. The first was the Mark of the Web (MOTW). I had added this to my HTML header sometime in the past, to gain Internet Exporer's trust for it not to bother me with requests to approve the running of ActiveX Controls:

<!-- saved from url=(0017)http://localhost/ -->

Removing this was part of the trick - the other part was to adjust my browser settings to allow cross-domain access:

That then allowed my client code to run and actually get results. Here's the HTML code for the page:

<html>

  <head>

    <title>Freewheel</title>

    <style>

      legend      { font-size: 10pt;

                    font-family: Calibri, Arial;

                    color: black; }

      button      { font-size: 10pt; }

      input      { font-size: 10pt;

                    font-family: Calibri, Arial; }

    </style>

    <script type="text/javascript">

      var freewheel =

        'http://freewheel.labs.autodesk.com';

      var http_request = false;

      var xmldoc;

      var path;

      function makeRequest(url)

      {

        try

        {

          http_request =

            new ActiveXObject("Msxml2.XMLHTTP");

        }

        catch (e)

        {

          try

          {

            http_request =

              new ActiveXObject("Microsoft.XMLHTTP");

          }

          catch (e)

          { }

        }

        if (http_request)

        {

          http_request.onreadystatechange = alertContents;

          http_request.open('GET', url, true);

          http_request.send(null);

        }

      }

      function alertContents()

      {

        if (http_request.readyState == 4)

        {

          if (http_request.status == 200)

          {

            var string = http_request.responseText;

            var xmldoc;

            xmldoc = http_request.responseXML;

            var secs =

              xmldoc.getElementsByTagName(

                "unsignedInt"

              )[0].firstChild.nodeValue;

            createViews(secs);

          }

          else

          {

            alert('There was a problem with the request.');

          }

        }

      }

      function replaceAll(strText, strTarget, strSubString)

      {

        var intIndexOfMatch = strText.indexOf( strTarget );

        while (intIndexOfMatch != -1)

        {

          strText = strText.replace( strTarget, strSubString )

          intIndexOfMatch = strText.indexOf( strTarget );

        }

        return( strText );

      }

      function createViews(sheets)

      {

        var container = document.getElementById('views');

        var htm = '<table width="620"><tr><td>';

        for(i=1; i<= sheets; i++)

        {

          htm += '<fieldset><legend>Sheet ' + i + '</legend>'

          htm += '<table><tr><td valign="middle">';

          htm += '<fieldset><legend>Clickable Thumbnail</legend>'

          htm += '<a href="' + freewheel + '/dwf.aspx?'

          htm += 'sec=' + i + '&dwf=' + path + '" target="New">';

          htm += '<img frameborder="0" height="150" ';

          htm += 'width="200" scrolling="no" src="' + freewheel;

          htm += '/dwfImage.aspx?page=' + i + '&';

          htm += 'width=200&height=150&path=' + path + '"/>'

          htm += '</a></fieldset>';

          htm += '</td><td>';

          htm += '<iframe frameborder="0" height="300" ';

          htm += 'width="400" scrolling="no" src="' + freewheel;

          htm += '/dwf.aspx?sec=' + i + '&dwf=' + path + '">';

          htm += '</iframe>';

          htm += '</td></tr>';

          htm += '</table></fieldset>';

        }

        htm += '</td></tr><table>';

        container.innerHTML = htm;

      }

      function OnGenerateSheetViews()

      {

        path = document.getElementById('URL').value;

        var url = freewheel + '/dwfrender.asmx/sectionCount?path=';

        var dwf = path;

        dwf = replaceAll(dwf, '/', '%2F');

        dwf = replaceAll(dwf, ':', '%3A');

        url += dwf;      

        makeRequest(url);

      }

    </script>

  </head>

  <body bgcolor="#E6E6E6">

    <input

      type="text"

      id="URL"

      size="60"

      value="http://through-the-interface.typepad.com/presentations/DWF/solids.dwf" /

    >

    <input

      id="GenerateSheetViews"

      type="button"

      value="Generate Sheet Views"

      onclick="return OnGenerateSheetViews()" /

    >

    <div id="views"></div>

  </body>

</html>

You'll notice that the page is nearly all script: the static elements are minimal - just somewhere to enter the URL of our DWF file and a <div> for our DHTML tags to be squirted into.

When the page loads there's not a great deal to see:

And it generates our sample pretty successfully:

The application comes into its own when we run it with a DWF with lots of sheets: the sample file, http://freewheel.autodesk.com/sample/Hotel5.dwf, has 29 sheets in case you really want to put it through its paces. :-)

Additional note:

A colleague kindly reminded me about something I had meant to mention. The code in this post makes use of the Autodesk Labs Freewheel server (http://freewheel.labs.autodesk.com). When you're developing applications based on Freewheel, you should really use the production Freewheel server (http://freewheel.autodesk.com), wherever possible. I used the Labs version (which is hosted on a single server, rather than being on a load-balanced, production-capable server farm) simply because it was able to render the specific DWF I was hosted in my site: fixes are generally rolled out first on the Labs server and migrate over time to the production server, as you'd expect, and in this case my DWF wasn't yet viewable via the production system.

To adjust the above code to use the production server, simply change the value of the "freewheel" variable:

var freewheel =

  'http://freewheel.autodesk.com';

AU Handouts: Enriching Your DWF™ - Part 2

[This post continues from part 1 of this series. The source for the below applications is available here: DWF Toolkit application source, Design Review application source & Freewheel application source.]

Mining the data with the DWF Toolkit

Now we’re going to look at using the DWF Toolkit – the freely available, cross platform toolkit for creating and reading DWF files – to extract the “identity” and “material” metadata associated with our geometry.

The DWF Toolkit is a C++ toolkit, so we have two components to our project:

1. A C++ DLL that uses the DWF Toolkit to read a DWF, storing the data we care about in XML
2. A VB.NET module that implements a user interface for viewing the XML content.

By its nature, DWF Toolkit client code tends to be somewhat complex, as it closely follows the internal structure of the DWF format, so I’m not going to go into the code. I will just say that you need to be a competent C++ programmer to work with the DWF Toolkit – it is not for the casual developer to dip into. There are clearly cases where using the DWF Toolkit makes a lot of sense – such as using it to modify or post-process DWFs non-graphically - but where possible I would recommend using a “higher level” API such as the API to Design Review or the publishing APIs within AutoCAD (just as we saw earlier).

The full source code for the project is posted to my blog, and here is what the application looks like:

Figure 12 – a DWF Toolkit application to extract our metadata

Linking 2D with 3D DWF data in an application embedding Design Review

In the next part of our demo, we’re going to make use of the metadata embedded in our DWF file to link the 2D and 3D sheets of our DWF.

Emedded 2D and 3D view onto DWF data actually have quite different API capabilities: 2D views have a set of events that you can respond to, to determine when objects are hovered over or selected (which you cannot receive for objects in 3D views), while 3D views allow you to manipulate object visibility and transparency (something you cannot control for objects in 2D views).

So we’re actually going to play to the strengths of the two API sets: we’re going to respond to an event when objects are hovered over in the 2D view, and during that callback we’re going to manipulate the 3D view to “isolate” the object in that view. And the way we’re going to link the two views is via the metadata that’s attached to our objects.

The HTML code is too long to include in its entirety here, so I’m going to describe the overall functionality and leave it to the reader to work through the code at their own pace. I will post the full source in a blog entry, though (as well as making it available for download there).

One of the key things is that in our “OnOverObject” callback (which we respond to with JavaScript code in our HTML), is that we receive a geometry index (a node ID) for the object that’s being hovered over. This, in itself, isn’t directly useful, so we need to find a way to map it to the objects in question. I managed to do this by hosting the object identity (handle) metadata in a combobox, populated in the same order as the geometry IDs we receive. So it’s very important that we populate the combobox appropriately, even if it’s hidden (which in our case it isn’t – we also make it available for the user to select objects by their handle).

Let’s look at how we embed our two views – both onto the same DWF file. Here’s the object tag for the 3D view:

<object

  id="ObjectView"

  width="100%"

  height="100%"

  classid="clsid:A662DA7E-CCB7-4743-B71A-D817F6D575DF"

  codebase= "http://www.autodesk.com/global/dwfviewer/installer/DwfViewerSetup.cab#version=7,0,0,928"

  VIEWASTEXT

>

  <param name="src" value="solids.dwf?section=1">

</object>

We have used the src property to set the appropriate section by using “?section=1” to specify the first one.

With the 2D sheet we’ve taken a slightly different approach:

<object

  id="Canvas"

  width="100%"

  height="100%"

  classid="clsid:A662DA7E-CCB7-4743-B71A-D817F6D575DF"

  codebase= "http://www.autodesk.com/global/dwfviewer/installer/DwfViewerSetup.cab#version=7,0,0,928"

  VIEWASTEXT

>

  <param name="src" value="solids.dwf">

</object>

We have not selected the sheet here – to avoid timing issues we’ve done so in the EndLoadItem JavaScript callback of the 2D view’s document:

if (Canvas.SourcePath != "solids.dwf?section=2")

{

  Canvas.SourcePath = "solids.dwf?section=2";

}

Much of the rest of the code is around user interface tweaks, such as forcing the “Orbit” mode by default in the 3D view, and the “Select Object” mode in the 2D view. We also disable the toolbars etc., to reduce dialog clutter.

Figure 13 - embedding and linking multiple Design Review windows in an HTML application

Hosting an embedded Freewheel view in a custom web-page

Freewheel – and its Labs sibling, Project Freewheel – is a zero-client AJAX (Asynchronous JavaScript and XML) technology for working with both 2D & 3D DWF content. The DWF file resides on a server – whether uploaded securely by the user or hosted on a publicly-accessible web-page – and the graphics for the current view on the DWF content are piped down to the HTML client via raster. It’s impressively responsive, even when orbiting in 3D.

We don’t get the same ability to view and work with metadata (at least not right now), but it is still a compelling experience if you want to embed lightweight navigation for DWF without forcing an install of Design Review on the client machine. It’s also getting some very cool collaborative review capabilities, to allow multiple people to mark 2D or 3D designs up in real-time. Very cool stuff, but not today’s subject, I’m afraid.

The first thing is to get our design into Freewheel. One option is to use the “Share Now” utility available from Autodesk Labs, which publishes to DWF and uploads to Freewheel, or we could upload it via the Freewheel user-interface, as we have a DWF file ready-to-go.
In our case, however, I’ve already posted a version of the DWF file to a publicly-accessible internet location, so we’re going to use that:

http://through-the-interface.typepad.com/presentations/DWF/solids.dwf

A quick note on using Autodesk Freewheel vs. Project Freewheel. Autodesk Freewheel (http://freewheel.autodesk.com) is the production environment for Freewheel, and is hosted on a high-availability, load-balanced server farm. Project Freewheel (http://freewheel.labs.autodesk.com) is hosted on a PC under someone’s desk (OK, that’s an exaggeration :-), but contains the latest & greatest functionality. I’ve found that the DWF files I’ve been creating for this demo are best viewed with the Project Freewheel server, so I’m using that, today, but I recommend you first try with the production system when implementing your own Freewheel-powered sites.

The two basic approaches for including a Freewheel view in your website are to link or to embed. Linking is simple: you create a standard HTML link with a URL pointing Freewheel to your DWF file:

<a href="http://freewheel.labs.autodesk.com/dwf.aspx?dwf=http://through-the-interface.typepad.com/presentations/DWF/solids.dwf">My link</a>

This creates a straight link to the Freewheel view. As with any HTML link, you can choose to launch this in a new window using the target property. You might also want to show a different page – you do this using the “sec” argument, which is the page/sheet number starting from 1:

<a href="http://freewheel.labs.autodesk.com/dwf.aspx?sec=2&dwf=http://through-the-interface.typepad.com/presentations/DWF/solids.dwf">My link</a>

Next we’re going to embed a view. We do this using an HTML iframe:

<iframe

  frameborder="0"

  height="300"

  width="400"

  scrolling="no"

  src="http://freewheel.labs.autodesk.com/dwf.aspx?sec=2&dwf=http://through-the-interface.typepad.com/presentations/DWF/solids.dwf">

</iframe>

Once again, you can use the “sec” parameter to select a particular sheet. This creates a navigable view on your DWF file.

Aside from linking or embedding, Freewheel exposes an ever-growing set of web services APIs, to allow you to render a particular view of a DWF to raster or to get information about a DWF, such as the number of pages, etc.

We can use the dwfImage web service to get an image of a DWF to use as a thumbnail:

<img

  frameborder="0"

  height="150"

  width="200"

  scrolling="no"

  src=

"http://freewheel.labs.autodesk.com/dwfImage.aspx?page=1&width=200&height=150&path=http://through-the-interface.typepad.com/presentations/DWF/solids.dwf" /

>

We can throw these together and create a web-page that links from the sheet thumbnails to full instances of Freewheel, as well as embedding interactive views of the same sheets. (The HTML source for this page is posted on my blog – it’s not complicated, but too long to include here.)

Figure 14 – embedding and linking to Freewheel in a custom web-page

The code that defines the above page could actually be generated manually – and that’s the next bit of fun… :-)

Using AJAX you can call web services from your client code: there are limitations as to what you can do (especially with regards to security limitations accessing web services across domains - which will make a great advanced topic for my blog), but this should give you a rough idea of what’s possible. In the below sample we query the number of sheets for a particular DWF, and use DHTML to generate the tags that allow us to view the content, as in the above hard-coded sample:

Figure 15 – our Freewheel generator on load

Figure 16 – our completed Freewheel generator