Editing QuickDraw 3D (section)

==QD3D==
QD3D was designed from the start to operate on computers with considerably less power than workstations. This led to a concerted effort to cleanly separate the upper and lower layers of the API, with the lower-level RAVE system being closer to MiniGL from the start. This had the advantage of providing a clean and minimal API that could be more easily ported to different hardware.

Since only RAVE needed to be ported, the upper layer APIs could be made as complex as desired, and the QD3D system included a complete scene graph, a standardized model file format, 3DMF, and even basic GUI objects that utilized them. To write a simple application in QD3D, the programmer only had to include a few libraries and then place the GUI elements in their program using [[ResEdit]] or similar tools.

Additional functionality included a "plug-in" rendering system, which allowed an application to render a scene in a variety of styles. Without changing the model or their code, developers could render the same scene interactively or (with suitable plug-ins) using methods such as ray-tracing or phong shading.

The QD3D API was an object-like system based on pure-[[C (programming language)|C]] code. The various structures were carefully constructed to contain pointers to other important objects. Objects knew all the drawing state they needed, thereby eliminating code that would normally be needed when developing under OpenGL.

On the downside, QD3D's layering introduced performance issues. For instance, the system stored and automatically set state for every object before drawing. This made development much easier, but also made the performance drop in a way the developer had no direct control over. Those applications demanding performance over ease of programming could instead choose to use the RAVE layer directly.

Another area of concern is that the scene graph was hidden from view, and considerable improvements in rendering performance can be made by carefully "culling" the graph to remove those objects that are not in view. Although later releases of QD3D gained the ability to automatically perform visibility culling (based on the grouping of objects in the scene graph), OpenGL's lack of support for this feature typically forced developers to implement it from the start.