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QuickDraw 3D: A New Dimension for Macintosh Graphics

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QuickDraw 3D is a new technology that helps developers bring 3D capabilities to their applications. It runs on all Power Macintosh computers and offers high-performance 3D rendering and other features that make working with 3D data easier. This article gives the basics you'll need to use QuickDraw 3D in your application, whether you're a consummate 3D developer, a classic 2D application

developer, or a game developer.

QuickDraw 3D is the newest enhancement to the Macintosh graphics architecture. Developers have been requesting a 3D library, supported at the system level, since the Macintosh was introduced. Although a number of Macintosh developers have produced some amazing 3D applications, 3D graphics capabilities were relegated to niche applications due to the lack of support at the core operating system level. QuickDraw 3D, which is expected to ship in mid-1995, brings the ability to deal with 3D graphics to all Power Macintosh applications: not only can traditional 3D applications take advantage of it, but it provides base functionality for general-purpose applications as well.

QuickDraw 3D is a Code Fragment Manager-based shared library, with a C-based API. Here we'll cover some concepts you need to know to get basic QuickDraw 3D support into your application. This issue's CD contains a prerelease version of the QuickDraw 3D shared library, the 3D Viewer shared library, programming interfaces, preliminary Inside Macintosh: QuickDraw 3D documentation, sample code, utility libraries, and other goodies. Two of the sample programs are discussed in this article.

    The API described in the article is based on a beta version of QuickDraw 3D; although nearly final, the API may change before the final release of the software.

In addition, we'll talk about reading and writing data in QuickDraw 3D metafile format, which is a way of representing 3D data in a consistent, transferable manner. But first we'll set the stage with some background information.


As we'll explain further in this article, QuickDraw 3D provides developers with a number of benefits:

  • a rich set of high-level geometries

  • built-in renderers that cover the base functionality needed by developers

  • immediate and retained graphics

  • a common 3D file format

  • human interface guidelines and widgets

  • a 3D pointing-device manager that provides support for input devices with more than two degrees of freedom

  • pointing and picking support that enables user selection of 3D data

  • transparent access to graphics accelerators

  • an extensible, plug-in shading and rendering architecture

  • implementation advantages over other 3D libraries

We've made

dealing with 3D data in applications easier with QuickDraw 3D. By creating a standard for data interchange, with a well-rounded metafile definition, we're enabling applications to read and write 3D data in a consistent format. The metafile specification addresses requests from both end users (who couldn't exchange data between applications in a common format) and developers (who had

to write special-case code to deal with several different file formats).

QuickDraw 3D comes with a set of human interface guidelines to foster the adoption of a consistent look and feel between applications (see "The QuickDraw 3D Human Interface"). 3D applications today are geared toward the trained 3D expert; what you learn in one application is generally not transferable to another application. By following the QuickDraw 3D human interface guidelines, however, developers can help make 3D graphics an integral part of the user experience within their applications.



    QuickDraw 3D provides human interface guidelines (in version 1.0) and a toolkit for implementing the guidelines (to come in the second major release). A sample application on this issue's CD illustrates our current ideas for a 3D human interface. By getting a preview of our plans, you can start taking your applications along the common path.

    Our main goal is to provide integration into the Macintosh experience. We feel that 3D graphics will be the next popular multimedia data type -- in the way that 2D graphics, sound, and movies have been in the past -- and users will want to incorporate 3D data into their documents in the same way that they can now incorporate other multimedia data types. To do this they'll need an interaction model built on the 2D principles that they're familiar with.

    Our guidelines offer suggestions and examples of how things can be done. If your applications are targeted for a very specific audience, and you know that audience well, you may decide to communicate with them in a different way, and that's perfectly OK.

    One of our guidelines, about direct manipulation through the use of a widget, is illustrated in Figure 1. Here we've appropriated the 2D grab handles that are popular in many "draw" programs and extended them to 3D. A widget is a set of handles for control of spatial parameters. Some widgets, such as the scale tool shown in Figure 1, indicate selection of a shape, while others make an invisible object, such as a light or a camera, visible.


    Figure 1. A scaling widget

    Figure 2 shows what a full-featured 3D application might look like. The emphasis here is on what's the same as in 2D applications rather than on what's unique. The illustration shows a shape selected with a rotation widget, a material selection palette, a room metaphor, and a document containing multiple views of a scene.


    Figure 2. Conceptual sketch of a 3D application>

QuickDraw 3D technology has been made possible in part by the dramatic performance improvements in the Power Macintosh line of computers. The performance of QuickDraw 3D is scalable across the Power Macintosh line; we've put in a lot of effort to ensure that the performance on even entry-level computers is excellent. With hardware acceleration, these computers can easily compete (and win) against mid-range workstations costing a lot more money.


QuickDraw 3D offers many advantages over other 3D libraries. When using other graphics libraries, you're on your own if, for instance, you want to change the way a scene is rendered (say, by doing ray tracing or applying procedural shading): you have to reimplement all of the 3D architecture. With QuickDraw 3D, you only have to write code to deal with the specific area that you want to change. And, even better, the code you write can be used as a plug-in by other


Unlike some libraries, QuickDraw 3D will be able to take advantage of a number of 3D hardware acceleration solutions, since acceleration was one of its design criteria. Another important criterion was cross-platform support. For example, a renderer could be written to take advantage of low-level 3D libraries, such as the Silicon Graphics OpenGL graphics library.


The 3D application development process can be broken down into four areas: creation of 3D data into a set of data structures, manipulation of that data in the human interface of the application, presentation of the data by displaying it, and transportation of the data (saving to and reading from files). QuickDraw 3D provides support in each of these areas. You can implement one or more of them in your application:

  • QuickDraw 3D geometries -- If you're planning to write an application to deal with the creation of models, QuickDraw 3D lets you define the representation of the objects to be modeled in 3D form.

  • QuickDraw 3D human interface -- Maybe you want to allow users to visualize 3D data and models in a standalone application or as part of an existing application. QuickDraw 3D's human interface guidelines and built-in widgets provide a consistent way of manipulating 3D objects.

  • QuickDraw 3D rendering and shading -- Rendering turns the 3D geometries into pixels; shading determines what color those pixels should be. Realism can be added by applying textures to objects: texture mapping takes a texture (usually from a picture source, such as a picture of a brick wall) and wraps it around an object. For example, Figure 3 shows a dinosaur mesh rendered with a skin texture picture as a texture map. In its second major release, QuickDraw 3D will enable you to write plug-in renderers and shaders and license them to other developers.


Figure 3. Dinosaur mesh mapped with a skin-like texture

    The dinosaur model was supplied in QuickDraw 3D metafile format courtesy of Viewpoint DataLabs Intl.
  • QuickDraw 3D metafile format -- If you want to provide 3D clip art in the form of models, you'll really be pleased with QuickDraw 3D's metafile format. One of the common problems encountered by users when working with several 3D applications is that of data interchange, where one application's file is not readable by another due to the multitude of 3D data formats. QuickDraw 3D addresses this problem by providing a standard for the interchange of 3D data. This device- and platform-independent representation of 3D data is extensible, so your custom data gets preserved. And all of the elements for a scene can be stored in the metafile, including lighting, camera objects, texture maps, and shaders.


Based on our experience working with developers, we've created a road map for adoption of QuickDraw 3D. Here we'll look at how different application developers might begin to adopt QuickDraw 3D, in order from the least to the greatest amount of support. These categories provide you with a general strategy for bringing QuickDraw 3D into your applications.

  • Developers of general-purpose 2D applications should add support for the metafile format, enabling users to read and save 3D data within an application. This can be achieved by using the 3D Viewer, which allows 3D objects derived from metafile data to be viewed and manipulated by the user.

  • Developers who use other 3D libraries and may not be ready to move to QuickDraw 3D just yet should at least add support for the metafile format and additionally consider adopting the QuickDraw 3D human interface guidelines. Obviously, support for the metafile format requires writing a parser to convert metafile data to another internal representation (Apple will be supplying parser code). Implementing the human interface guidelines will make the application be compatible with and look consistent with other 3D applications available on the Macintosh. Note that an application that uses a 3D library other than QuickDraw 3D will have a harder time using the 3D Viewer.

  • Developers of existing 3D applications who want to take the first step toward creating a QuickDraw 3D-savvy application should take advantage of QuickDraw 3D's rendering capabilities through the use of immediate-mode rendering (more on this later). This method provides not only fast rendering in software but also transparent access to hardware, while allowing the application to preserve its own data structures. In addition, these developers should plan to add support for the metafile format and the human interface guidelines.

  • Developers who want to leave the low-level work to QuickDraw 3D, and concentrate on creating differentiating features within their applications, should make their applications as QuickDraw 3D-savvy as possible. This means taking advantage of the full API, including QuickDraw 3D's data structures and geometries (which provide metafile support virtually for free), rendering (both immediate and retained modes), and the human interface guidelines.


The QuickDraw 3D architecture isolates in a layer within the system software those things that all developers have to do, leaving them to concentrate on the code that will allow their application to stand out. This architecture can be thought of as a sandwich filling that sits between your application and the hardware it's running on, isolating you from having to deal with operating system and hardware issues directly. Like any good sandwich filling, if you examine it closely, you'll see that it's divided into a number of appetizing chunks. Figure 4 shows some of the functional blocks that make up QuickDraw 3D,

with an emphasis on those areas that can be customized by developers.


Figure 4. QuickDraw 3D architecture

Let's take a quick look at each of these functional areas, which we'll expand on later. Here we'll use the word scene to describe not only the objects being modeled, but also the lighting, camera settings, shaders, and other entities that affect the final appearance on output devices.

Widgets are used to enhance the user experience for 3D applications. For example, to allow the user to interact with an object, the application can draw grab handles, in the form of a translation widget, to allow the object to be manipulated.

Geometries are the encapsulation of data used to describe an object. Some geometries are provided as part of QuickDraw 3D, resulting in a very concise representation; for more information, see "QuickDraw 3D Geometries." (QuickDraw 3D uses geometries to draw widgets.)


    The QuickDraw 3D geometries that are currently available are as follows: line, polyline, triangle, point, simple polygon, general polygon, trigrid, mesh, box,

    marker, NURB curve, and patch.

    In addition, the following geometries are planned for the second major release of QuickDraw 3D: torus, ellipse, ellipsoid, disk, cylinder, cone, and triangle strip. (In version 1.0, you can create any of these geometries by representing them as meshes.)

    Where applicable, the geometries are parameterized so that they're ready for texture mapping or other shading effects.

The I/O layer provides support for metafiles. There are routines for reading and writing 3D data to Storage objects, which may be disk or memory based and are useful for providing Clipboard or drag and drop support in your


Picking is used to determine which object a user chose. QuickDraw 3D's picking facilities are more extensive than in other 3D libraries, not only providing several different types but also returning quite a bit of information to the application beyond whether a hit took place.

Light objects supply the lighting for a scene. QuickDraw 3D provides four types of light sources: ambient, directional, point, and spot. Based on the light sources for a given scene and the illumination shader, the renderer makes intensity calculations for each object's surface and vertex contained in the scene.

Camera objects define a point of view into a particular scene. QuickDraw 3D provides three different camera types: view angle, orthographic, and view plane.

Attributes are used to specify different characteristics for each object (or parts of an object, such as its vertices or faces), and also to attach custom data to an object.

Shaders are used to modify or add data, on either a per vertex or a per pixel basis, as geometries are being processed by the renderer -- for example, illumination and texturing shaders.

Renderers are the business end of QuickDraw 3D. A renderer is a set of routines used to create a shaded synthetic model of the scene, based on the information stored in the geometry and taking into account the lighting, surface attributes, and camera location. QuickDraw 3D provides two basic renderers: a wireframe and an interactive renderer. You can extend QuickDraw 3D by writing a plug-in renderer, developing an accelerator card, or implementing a combination of both -- a renderer tied to a particular hardware setup.


Now, on to the coding details. We realized that some application developers wouldn't want to get involved with the low-level details of a new API. We looked at the QuickTime model and saw that a lot of developers implemented support for viewing movie data by using movie controllers in their existing nonmultimedia applications. We likewise wanted to allow applications to support the viewing of QuickDraw 3D metafiles with minimal effort, so we've provided an additional shared library that implements a 3D Viewer. The Viewer allows users to view and have a basic level of interaction with 3D data without your having to make any QuickDraw 3D calls. Figure 5 shows a Viewer implementation in a modified version of the Scrapbook. (We used a preliminary version, so the

Viewer interface may change.)


Figure 5. Viewer implementation in the Scrapbook

    The car model was supplied in QuickDraw 3D metafile format courtesy of Viewpoint DataLabs Intl.

Adding Viewer support is simple -- it requires only about five function calls. Your application can check to see if the Viewer is available by calling Gestalt

with the constant gestaltQuickDraw3DViewer.

We'll now look at how your application can create and use a QuickDraw 3D Viewer object. In the application named Simple 3D Viewer on this issue's CD, we create a window in which the only object is a Viewer.

    As you read through the code samples, you'll notice that function names have a "Q3" prefix, data types have a "TQ3" prefix, and constants have a "kQ3" prefix. The part of a function name before the underscore indicates the object being operated on (the class), while the part after the underscore indicates the operation (the method). For example, to set the origin of a Box object, you'd call the function Q3Box_SetOrigin.


Creating and disposing of a Viewer object is very easy to do. You attach a Viewer to a window with the Q3ViewerNew function:

viewerObj = Q3ViewerNew((CGrafPtr)theWindow, &theRect, 0L); 

This function takes a WindowPtr, a pointer to a Rect that describes the window area where you want the 3D scene to appear, and a long word containing flags for modifying the behavior of the Viewer. When you're finished with the Viewer, you need to dispose of it with the Q3ViewerDispose function:



To display the contents of a metafile in your Viewer, you can use the Q3ViewerUseFile function:

Q3ViewerUseFile(viewerObj, fileRefNum);

Q3ViewerUseFile takes a reference to the Viewer object and a file reference to a previously opened QuickDraw 3D metafile. You can also display data from the Clipboard or data you created yourself, with the Q3ViewerUseData function:

Q3ViewerUseData(viewerObj, myDataPtr, myDataSize);

This function takes a reference to a Viewer object, a pointer to the data, and the size of the data in bytes. The data must be in metafile format.


You need to modify your event loop slightly to give the Viewer the opportunity to handle events, as follows:

wasViewerEvent = Q3ViewerEvent(viewerObj, theEvent);

Q3ViewerEvent takes a reference to a Viewer object and a pointer to an event record (usually obtained from WaitNextEvent). This function allows the Viewer to respond to events, such as a mouse-down event in one of its controls. It returns a value

of type Boolean that indicates whether the event was handled.

If the area occupied by the Viewer needs to be updated, you need to redraw the data in your update event handler by calling Q3ViewerDraw:

theErr = Q3ViewerDraw(viewerObj);


The Viewer allows access to the View object for the scene, which enables you to customize the Viewer's behavior by changing the renderer or lighting for the scene (more on Views later). Also, the Viewer provides support for cut, copy, and paste; see the Simple 3D Viewer sample on the CD for an example.


Now let's look at programming with the QuickDraw 3D API, starting with error checking and initialization. First, the QuickDraw 3D shared library needs to be installed in the Extensions folder or in the same folder as your project. During your development cycle you should use the debugging version of the

library for extensive error checking.

Error checking may seem like a weird place to start, but checking and responding to what QuickDraw 3D is trying to tell you will save a great deal of trouble and strife during development. The QuickDraw 3D error manager provides several levels of error checking along with functions for checking the last error that occurred. The error checking, which is similar to that in QuickDraw GX, has three levels: errors, warnings, and notices.

  • Errors are the most severe indication of a problem and can be divided into two kinds, fatal and nonfatal. You can determine whether an error is fatal with the call

    TQ3Boolean Q3Error_IsFatalError(TQ3Error theError);

    For a complete list of errors provided by QuickDraw 3D, look in the QuickDraw 3D header files.

  • Warnings are less severe than errors, but you should be prepared to handle them. If the system generates a warning based on a recoverable situation that you ignore, often an unrecoverable error may occur later.

  • Notices indicate problems that may exist with the way you're using the QuickDraw 3D library. Although they're less severe than warnings, you should take note of what notices are telling you, to prevent problems from occurring later in your application's execution. Notices are generated only in the debugging version.

You can install your own error, warning, and notice handlers, which can write the error information to a window or file or present a dialog or alert. Presenting too many alerts can be annoying to the user, so you should probably log errors, warnings, and notices to a file or a status window, and present a dialog or an alert only for fatal errors from which no recovery is possible.


Handlers for errors, warnings, and notices are all similar -- they're functions that take an error code of type TQ3Error and have no return value. Listing 1 shows a definition of an error handler.

Listing 1. Error handler

static void MyErrorHandler(TQ3Error firstError, TQ3Error lastError,
                           long refCon)
   char   buf[512];

   sprintf(buf, "ERROR %d - %s\n", lastError, 
         getErrorString(lastError));      // Get the error as a C string.
   if (gErrorFile == NULL)
      gErrorFile = fopen("error.output", "w+");
   if (gErrorFile != NULL)
      fputs(buf, gErrorFile);

Once handlers have been defined, it's a snap to install them. For example, you would install the error handler defined in Listing 1 as follows:

Q3Error_Register(MyErrorHandler, 0L);


Before you can use QuickDraw 3D, you need to call Gestalt to see if the library is installed, using the constant gestaltQuickDraw3D. You then need to initialize the library as shown in Listing 2. You call the Q3Initialize function to ensure that the QuickDraw 3D library gets a chance to allocate its internal data structures and to initialize any subcomponents (such as plug-in shaders) that it needs to call. You then do other initialization as needed, such as installing an error handler. The return value indicates whether the

call was successful.

Listing 2. Initializing and closing the connection to the library

void Initialize3DStuff(void)
   if (Q3Initialize() == kQ3Failure) {
      // Handle the error.
void Exit3DStuff(void)
   if (Q3Exit() == kQ3Failure) {
      // Handle the error.

When your application is about to quit, you should shut down your connection to the QuickDraw 3D library by calling Q3Exit, also shown in Listing 2. (Obviously a real application would have more sophisticated error handling here.)


The Box application on this issue's CD is a simple QuickDraw 3D program that opens a window, displays 3D boxes in the window, and rotates the boxes (see Figure 6). While this isn't a useful application as such, it covers all the basics needed to create and display objects using QuickDraw 3D. It also illustrates double buffering support, which helps an application provide flicker-free drawing when animating geometries; QuickDraw 3D's double buffering

takes advantage of hardware double buffering when available.


Figure 6. A window from the Box sample program

    For a more complex example, see the Modeller program on the CD, which shows most of the things a QuickDraw 3D application needs to do, such as reading and writing metafiles, texture mapping, and using interpolation styles.

We define the following data structure to store the information that QuickDraw 3D needs to model and render our scene:

struct _documentRecord {
	TQ3ViewObject		fView;				// The view for the scene
	TQ3GroupObject		fModel;				// Object in scene being modeled
	TQ3StyleObject		fInterpolation;	// Style used when rendering
	TQ3StyleObject		fBackFacing;		// Whether to draw shapes that face 
													// away from the camera
	TQ3StyleObject		fFillStyle;			// Drawn as solid filled objects or 
													// decomposed to components
	TQ3Matrix4x4		fRotation;			// The transform for the model
typedef struct _documentRecord DocumentRec, *DocumentPtr, **DocumentHdl;

We can create a new instance of this type, initialize it with the required values, and store a reference to it in each window's refCon field.


Creating a simple object -- like a box -- is straightforward. We'll make four copies of the box, each with its own transform. The code to create these boxes is shown in Listing 3. We can store the boxes in our document simply by storing

the value returned by this function in our document's fModel field.

Listing 3. Creating four boxes

TQ3GroupObject MyNewModel()
   TQ3GroupObject         myGroup;
   TQ3GeometryObject      myBox;
   TQ3BoxData            myBoxData;
   TQ3GroupPosition      myGroupPosition;
   TQ3ShaderObject      myIlluminationShader;
   TQ3Vector3D            translation;
   TQ3SetObject         faces[6];
   short                  face;

   // Create a group for the complete model.
   if ((myGroup = Q3DisplayGroup_New()) != NULL) {
      // Define a shading type for the group and add the shader to
      // the group.
      myIlluminationShader = Q3PhongIllumination_New();
      Q3Group_AddObject(myGroup, myIlluminationShader);   

      // Set up the colored faces for the box data.
      myBoxData.faceAttributeSet = faces;   
      myBoxData.boxAttributeSet = nil;

      // Create the box itself.
      Q3Point3D_Set(&myBoxData.origin, 0, 0, 0)
      Q3Vector3D_Set(&myBoxData.orientation, 0, 1, 0);
      Q3Vector3D_Set(&myBoxData.majorAxis, 0, 0, 1);   
      Q3Vector3D_Set(&myBoxData.minorAxis, 1, 0, 0);   
      myBox = Q3Box_New(&myBoxData);
      // Put four references to the box into the group, each one with 
      // its own translation.
      translation.x = 0; translation.y = 0; translation.z = 0;
      MyAddTransformedObjectToGroup(myGroup, myBox, &translation);
      translation.x = 2; translation.y = 0; translation.z = 0;
      MyAddTransformedObjectToGroup(myGroup, myBox, &translation);
      translation.x = 0; translation.y = 0; translation.z = -2;
      MyAddTransformedObjectToGroup(myGroup, myBox, &translation);
      translation.x = -2; translation.y = 0; translation.z = 0;
      MyAddTransformedObjectToGroup(myGroup, myBox, &translation);

   // Dispose of the objects we created here.
   if (myIlluminationShader != NULL) 
   for (face = 0; face < 6; face++) {
      if (myBoxData.faceAttributeSet[face] != NULL)
   if (myBox != NULL) 
   return myGroup;

Notice that we dispose of the boxes after adding them to the document group. [[QuickDraw 3D]] will create references to the boxes in the document group, so we can safely dispose of them. To be good QuickDraw 3D citizens and to make more effective use of memory, we need to dispose of each QuickDraw 3D object as soon as we're done with it. QuickDraw 3D keeps track of the reference count of each object to help detect memory leaks. If you're using the debugging version of QuickDraw 3D, it will tell you when you call Q3Exit if there are any objects remaining that need to be disposed of.


We talked earlier about retained and immediate modes. Which mode to use is the subject of big philosophical arguments in the world of 3D graphics. Some developers prefer one over the other as a matter of principle; other developers make a choice based on the type of application being developed. QuickDraw 3D offers the best of both worlds: not only does it support both ways of rendering geometric data, it also allows you to mix these types in the same rendering loop.

    Retained and immediate modes are simply methods of rendering, without the usual connotation of the term "mode" (a state that you must exclusively remain in once you get into it). Although this terminology has become common in the field of 3D graphics, retained rendering and immediate rendering calls can in fact be freely mixed.

In retained mode, the definition and storage of the geometries are kept internal to QuickDraw 3D (as an abstract object). This mode provides convenient features for caching, rejection of entire objects based on clipping and culling, preservation of tessellated surfaces, multiple instantiation of objects (drawing multiple versions of an object but storing its definition only once), and conversion between geometry types. Retained mode is useful when the geometry has to be passed around to different modules within the application or to plug-in renderers. Extensive geometry editing functions are provided as part of the QuickDraw 3D API, which makes it easy to alter the data associated with

each geometric object.

In immediate mode, the application keeps the only copy of the geometry. This is particularly useful when your application needs to reference data that's in a format different from the one used by QuickDraw 3D or when a large number of vertices that make up the geometry are being edited continuously -- for example, in the animation of a stress analysis for mechanical design.

The code in Listing 3 creates the boxes in retained mode, by creating objects that encapsulate the box data; QuickDraw 3D then manages the box data for us. If you want to add QuickDraw 3D rendering and drawing to an existing application with its own 3D data structures, you can draw in immediate mode instead. To draw a box in immediate mode, you simply initialize the values in the TQ3BoxData structure to the appropriate values and then draw the data directly in a rendering loop (described later) by calling the following function:

myStatus = Q3Box_Submit(&myBoxData);

Because you never create a QuickDraw 3D object, there's no need to call Q3Object_Dispose.

    Notice that in Listing 3 we initialize an object using a data structure of type TQ3BoxData. This structure contains all of the information required to draw a Box geometry, but is not an object in itself. Because of this we don't call Q3Object_Dispose on the box data structure, but we do call it on the Box object.


All window system dependencies are isolated to a layer we call the draw context. This makes porting your application easier (and it also makes it easier for us to port QuickDraw 3D to other platforms). Although QuickDraw 3D is platform independent, of course at some point you'll need to deal with the

realities of a particular platform's window system, in this case the Mac OS.

This is where the concept of a draw context comes in. It's a means for QuickDraw 3D to interface with the host environment. There's a special draw context for the Mac OS, called a Macintosh draw context; information describing this context is stored in a TQ3MacDrawContext object, which contains the information necessary for QuickDraw 3D to image the data on a computer running the Mac OS.

Listing 4 is a routine from the Box application that creates a Macintosh draw context the size of a window that we pass in. We're telling QuickDraw 3D to create a buffer in which to image the data; this is referred to as the back buffer. If we're using double buffering (that is, we set the doubleBufferState field of the Macintosh draw context to true), the front buffer will be the window associated with the draw context. The data is copied from the back buffer to the front buffer when Q3View_EndRendering is called. This helps provide flicker-free animation if you're animating the object being viewed.

Listing 4. Creating a Macintosh draw context

TQ3DrawContextObject MyNewDrawContext(WindowPtr theWindow)
   TQ3DrawContextData      myDrawContextData;
   TQ3MacDrawContextData   myMacDrawContextData;
   TQ3DrawContextObject      myDrawContext;
   TQ3ColorRGB             clearColor;

   Q3ColorRGB_Set(&clearColor, 1, 1, 1);
   myDrawContextData.clearImageState = kQ3True;
   myDrawContextData.clearImageMethod = kQ3ClearMethodWithColor;
   myDrawContextData.clearImageColor = clearColor;
   myDrawContextData.paneState = kQ3False;
   myDrawContextData.maskState = kQ3False;
   myDrawContextData.doubleBufferState = kQ3True;
   myMacDrawContextData.drawContextData = myDrawContextData;
   myMacDrawContextData.window = (CGrafPtr) theWindow;   // The window
                                          // associated with the view
   myMacDrawContextData.library = kQ3Mac2DLibraryNone;
   myMacDrawContextData.viewPort = nil;
   myMacDrawContextData.grafPort = nil;
   // Create draw context and return it; if nil, caller must handle it.
   myDrawContext = Q3MacDrawContext_New(&myMacDrawContextData);
   return myDrawContext;

Sometimes you might want to be able to get at the back buffer yourself; for example, you might want to create a picture preview of some metafile data to place on the Clipboard along with the metafile data, so that applications that don't support metafiles can display the picture. QuickDraw 3D makes this possible by providing a different type of draw context, called a pixmap draw context, which can be based on a GWorld. First you need to create a GWorld the size of the window area; then you can create a pixmap draw context as shown in Listing 5.

Listing 5. Creating a pixmap draw context

TQ3DrawContextObject MyNewPixmapDrawContext(GWorldPtr theGWorld)
   TQ3PixmapDrawContextData   myPixmapDCData;
   TQ3ColorRGB                  clearColor;
   PixMapHandle                hPixMap;
   Rect                        srcRect;
   Q3ColorRGB_Set(&clearColor, 1, 1, 1);

   // Fill in the draw context data.
   myPixmapDCData.drawContextData.clearImageState = kQ3True;
   myPixmapDCData.drawContextData.clearImageMethod =
   myPixmapDCData.drawContextData.clearImageColor = clearColor;
   myPixmapDCData.drawContextData.paneState = kQ3False;
   myPixmapDCData.drawContextData.maskState = kQ3False;
   myPixmapDCData.drawContextData.doubleBufferState = kQ3False;
   hPixMap = GetGWorldPixMap(theGWorld);
   srcRect = theGWorld->portRect;
   myPixmapDCData.pixmap.width  = srcRect.right  - srcRect.left;
   myPixmapDCData.pixmap.height = srcRect.bottom -;
   myPixmapDCData.pixmap.rowBytes  = (**hPixMap).rowBytes & 0x7FFF;
   myPixmapDCData.pixmap.pixelType = kQ3PixelTypeRGB32;
   myPixmapDCData.pixmap.pixelSize = 32;
   myPixmapDCData.pixmap.bitOrder  = kQ3EndianBig;
   myPixmapDCData.pixmap.byteOrder = kQ3EndianBig;
   myPixmapDCData.pixmap.image      = (**hPixMap).baseAddr;

   return Q3PixmapDrawContext_New(&myPixmapDCData);

When using a pixmap draw context, you must keep the GWorld's PixMap locked all the time (which implies that you need to call LockPixels on it, to help avoid heap fragmentation). Also, the PixMap must be 32 bits deep -- other depths are not supported.


A camera is a QuickDraw 3D object used to project a 3D scene onto a 2D plane. It defines a point of view on the scene and a method of projection onto the viewing plane. QuickDraw 3D provides three types of camera:

  • View angle or perspective -- This type of camera is defined in terms of a viewing angle and horizontal-to-vertical aspect ratio. It's the most common camera type because it provides a natural-looking perspective.

  • Orthographic -- This is a parallel projection, where the direction of projection is perpendicular to the projection plane. Orthographic projections are generally less realistic than perspective projections; however, they're popular for engineering drawings because parallel lines remain parallel in the projection, rather than converging to a single point on the horizon.

  • View plane -- This is a perspective projection defined in terms of an arbitrary viewing plane. This type of camera is useful for providing an off-axis view, which is used for scrolling.

We use a view angle camera for

the Box application, creating the camera with the routine in Listing 6.

Listing 6. Creating the camera

TQ3CameraObject MyNewCamera(WindowPtr theWindow)
   TQ3ViewAngleAspectCameraData   perspectiveData;
   TQ3CameraObject               camera;
   TQ3Point3D       from = { 0.0, 0.0, 13.0 };
   TQ3Point3D       to   = { 0.5, 0.5, -1.5 };
   TQ3Vector3D    up   = { 0.0, 1.0, 0.0 };
   float          fieldOfView = 0.523593333;
   float          hither      = 0.001;
   float          yon         = 1000;

   perspectiveData.cameraData.placement.cameraLocation = from;
   perspectiveData.cameraData.placement.pointOfInterest = to;
   perspectiveData.cameraData.placement.upVector = up;
   perspectiveData.cameraData.range.hither = hither;
   perspectiveData.cameraData.range.yon = yon;
   perspectiveData.cameraData.viewPort.origin.x = -1.0;
   perspectiveData.cameraData.viewPort.origin.y = 1.0;
   perspectiveData.cameraData.viewPort.width  = 2.0;
   perspectiveData.cameraData.viewPort.height = 2.0;
   perspectiveData.fov = fieldOfView;
   perspectiveData.aspectRatioXToY =
      (float) (theWindow->portRect.right - theWindow->portRect.left) / 
      (float) (theWindow->portRect.bottom - theWindow->;
   camera = Q3ViewAngleAspectCamera_New(&perspectiveData);

   return camera;


QuickDraw 3D includes a number of different light objects that can be used to provide illumination to the surfaces in a scene. Lighting is additive, meaning that the amount of lighting applied to a particular surface will be the sum of the lighting from all sources. There are four light types:

  • Ambient -- This is the amount of light added to all surfaces in a scene. Since this light type has no location, it doesn't cast shadows.

  • Directional -- Sometimes referred to as an "infinite" light, this light source emits parallel rays of light in a specific direction. The intensity of this light source doesn't change as the distance from the light changes.

  • Point -- This light source emits rays of light in all directions from a particular point location. A point light is attenuated, meaning that the intensity of the light decreases as the distance from the light increases; QuickDraw 3D provides a set of constants to control this behavior.

  • Spot -- This type of light emits a circular cone of light from a point source in a particular direction. A spot light is attenuated both by the distance from the source and by the position across the cone; the intensity of light at the center of the cone is greater than the intensity at the edge of the cone.

Listing 7 shows an extract from our sample's MyNewLights routine;

here we create a point light and add it to a light group.

Listing 7. Creating a point light in a light group

lightGroup = Q3LightGroup_New();

pointData.lightData.isOn = kQ3True;
pointData.lightData.brightness = 0.80;
pointData.lightData.color.r = 1.0;
pointData.lightData.color.g = 1.0;
pointData.lightData.color.b = 1.0;
pointData.location.x = -10.0;
pointData.location.y = 0.0;
pointData.location.z = 10.0;
pointData.castsShadows = kQ3False;
pointData.attenuation = kQ3AttenuationTypeNone;
light = Q3PointLight_New(&pointData);

Q3Group_AddObject(lightGroup, light);



Once you've added the light to a group, you can associate the group with the View object for your scene. A View object keeps track of the information necessary to render an entire scene, tying together the different parts of QuickDraw 3D. In our simple example it ties together the draw context, camera, lights, and renderer. Listing 8 shows the code we use to create the View object

for the Box program.

Listing 8. Creating the View object

TQ3ViewObject MyNewView(WindowPtr theWindow)
   TQ3Status               myStatus;
   TQ3ViewObject            myView;
   TQ3DrawContextObject      myDrawContext;
   TQ3RendererObject         myRenderer;
   TQ3CameraObject         myCamera;
   TQ3GroupObject            myLights;
   myView = Q3View_New();
   // Create and set the draw context.
   myDrawContext = MyNewDrawContext(theWindow);
   myStatus = Q3View_SetDrawContext(myView, myDrawContext);
   // Create and set the renderer. Use the interactive software renderer.
   myRenderer = Q3Renderer_NewFromType(kQ3RendererTypeInteractive);
   myStatus = Q3View_SetRenderer(myView, myRenderer);
   // Create and set the camera.
   myCamera = MyNewCamera(theWindow);
   myStatus = Q3View_SetCamera(myView, myCamera);
   // Create and set the lights.
   myLights = MyNewLights();
   myStatus = Q3View_SetLightGroup(myView, myLights);

   return myView;


All drawing must be done in a rendering loop. This is necessary because we don't know in advance how much memory is required to render a complex model. The loop should fit neatly into your application, because most Macintosh applications will localize drawing in the update event-handling code, which is where you'll call your rendering loop for QuickDraw 3D. A simple rendering loop

will look like Listing 9.

Listing 9. The rendering loop

TQ3Status DocumentDraw3DData(DocumentPtr theDocument)
   do {
      Q3Style_Submit(theDocument->fInterpolation, theDocument->fView);
      Q3Style_Submit(theDocument->fBackFacing, theDocument->fView);
      Q3Style_Submit(theDocument->fFillStyle, theDocument->fView);
      Q3DisplayGroup_Submit(theDocument->fModel, theDocument->fView);
   } while (Q3View_EndRendering(theDocument->fView) 
                     == kQ3ViewStatusRetraverse);
   return kQ3Success;

Recall that earlier we set up our Macintosh draw context to use double buffering; this causes all drawing to take place in the back buffer. The calls in the rendering loop draw into the active buffer, which we have set up to be the back buffer. The image data is copied from the back buffer to the front buffer (in this case

the window) when Q3View_EndRendering is called.

A rendering loop for a pixmap draw context would be similar to the routine in Listing 9, except you would need to copy the data from your PixMap to the screen yourself, generally with CopyBits.


Here we'll take a brief look at the architecture of QuickDraw 3D's metafile format (file type '3DMF') and at how you can provide metafile support in your


The QuickDraw 3D metafile comes in two forms: plain-text (ASCII) and binary. Table 1 shows the differences between these two forms. The plain-text form is more useful for debugging purposes; once your application is debugged, it's more efficient to use the binary form, which may be read and written much faster and may require less storage space on disk.


The metafile format supports a wide range of primitive data types, including 1-, 2-, 4-, and 8-byte signed and unsigned integers and 4- and 8-byte IEEE floating-point numbers, together with a range of types for describing 3D data. In addition, metafiles may contain big- or little-endian numbers, making them ideal for storing data that may be used in a cross-platform manner.


There are three distinct types of metafile organization: normal, stream, and database. The organization of the file can affect both the size of the file and the time it takes to access the data in the file. Let's look at a simple example in which a single Box object is drawn four times at different positions by means of four different Transform objects, as was shown in Figure 6. The three types of organization are illustrated in Figure 7. (Note that # marks the beginning of a comment.) These types are as follows:

  • Normal -- This is the most compact representation. Referenced objects are listed in a Table of Contents (TOC). In our example, only the Box object is listed in the TOC. The Transform objects don't appear in the TOC because they were referenced only once. Note that random access to the file is needed to resolve references, since after reading a reference, the metafile parser needs to skip forward to the TOC, and back to resolve the references.

  • Stream -- There is no TOC, and references to objects are written as copies of the objects themselves. This may result in a larger file if a lot of object references were used, but it allows for a sequential search. A sequential search is very useful for reading from the file and imaging to a printer, since each object can be read, imaged, and disposed of. This organization is also useful as a wire protocol for imaging on remote machines.

  • Database -- Every object is logged into the TOC, even if it's not referenced. Each TOC entry contains the type of the object. Accessing the TOC lets you see all the information contained in the file without having to read in all of the file and create objects. This would be useful for creating a catalog of textures, for example.

(image missing)

Figure 7. Three types of metafile organization (representing Figure 6)


The simplest way to access data in metafiles is to use the QuickDraw 3D API. First, there are two types of objects you need to understand:

  • TQ3FileObject -- Objects of this type maintain state information and provide an interface between a given file format and a Storage object. File objects are used to read and write data in metafile format from and to Storage objects.

  • TQ3StorageObject -- Objects of this type act as an interface to a type of physical stream-based storage (for example, memory and files). Storage objects are used to represent a piece of physical storage.

Why have this

two-stage approach? The answer is that all the machine dependencies are localized in the Storage object, which allows files to be used to read and write data from differing types of physical storage with the same set of routines. For example, you can use the same File object to write to a Storage object that represents a file on your hard disk and to write to another Storage object that represents a block of memory that will be passed to the Scrap Manager.

The usual method for using File and Storage objects is to create a new instance of a Storage object and attach it to a newly created File object using Q3File_SetStorage, as shown in Listing 10.

Listing 10. Attaching a Storage object to a file

TQ3FileObject MyGetNewFile(FSSpec *myFSSpec, TQ3Boolean *isText)
   TQ3FileObject      myFileObj;
   TQ3StorageObject   myStorageObj;
   OSType            myFileType;
   FInfo               fndrInfo;

   // We assume the FSSpec passed in was valid and get the file
   // information. We need to know the file type; this routine may get 
   // called by an Apple-event handler, so we can't assume a type -- we 
   // need to get it from the FSSpec.
   FSpGetFInfo(myFSSpec, &fndrInfo);
   myFileType = fndrInfo.fdType;

   if (myFileType == '3DMF')
      *isText = kQ3False;
   else if (myFileType == 'TEXT')
      *isText = kQ3True;
      return NULL;
   // Create a new Storage object and new File object.
   if (((myStorageObj = Q3FSSpecStorage_New(myFSSpec)) == NULL) 
         || ((myFileObj = Q3File_New()) == NULL)) {
      if (myStorageObj != NULL) 
      return NULL;

   // Set the storage for the File object.
   Q3File_SetStorage(myFileObj, myStorageObj);

   return myFileObj;

Reading data from metafiles. There are three routines that you can use to help with reading the data: Q3File_GetNextObjectType, Q3File_ReadObject, and Q3File_SkipObject. Listing11 illustrates the technique used to read drawable data from a metafile. The code loops through the file, getting each object and checking to see if the object is drawable; if so, it adds the object

to a group object.

Listing 11. Reading from a metafile

TQ3Status MyReadModelFromFile(TQ3FileObject theFile, TQ3GroupObject
   if (theFile != NULL) {
      TQ3Object      myTempObj;
      TQ3Boolean      isEOF;
      // Read objects from the file.
      do {
         Q3File_ReadObject(theFile, &myTempObj);
         if (myTempObj != NULL) {
            // We want the object in our main group only if we can 
            // draw it. 
            if (Q3Object_IsDrawable(myTempObj)) 
               Q3Group_AddObject(myGroup, myTempObj);
            // We either added the object to the main group, or we don't 
            // care, so we can safely dispose of it.
         // Check to see if we've reached the end of the file yet.
         Q3File_IsEndOfFile(theFile, &isEOF);
      } while (isEOF == kQ3False);   
   if (myGroup != NULL)
      return kQ3Success;
      return kQ3Failure;

Because we're isolating the implementation details of how the metafile data is stored in the Storage object that we associated with the File object at its creation time, we don't care how the metafile data we're reading is physically stored. What this means is that we could use the routine above to read data from the scrap, from a handle supplied by the Drag Manager, or from a file, as long as

the storage object attached to the file is set up properly.

Writing data to metafiles. Data is written to files similarly to the way it's drawn in a rendering loop. Depending on the available memory and the complexity of the model, QuickDraw 3D may need to traverse the model in the group more than once in order to write all the data out (this is the same reason that the rendering needs to be done in a loop). As shown below, you need to preface your file-writing loop with a call to Q3File_BeginWrite, and test the value returned by Q3File_EndWrite to see if there's a need to traverse the data again.

Q3File_OpenWrite(file, kQ3FileModeNormal);
do {
	Q3Object_Write(group, file);
} while (Q3File_EndWrite(file) == kQ3FileStatusRetraverse);


QuickDraw 3D lowers the bar for application developers who want to put support for 3D data into their applications. By providing support for the features that all developers need to have in applications -- geometries, metafile support, rendering, and human interface -- QuickDraw 3D allows you to concentrate on the features and facilities that set your application apart.