Quartz Composer

Quartz Composer is a node based visual programming language provided as part of the Xcode development environment in Mac OS X v10.4 "Tiger" for processing and rendering graphical data.

Quartz Composer uses OpenGL, Core Image, Core Video, and other technologies to build an API and a developer tool around a simple visual programming paradigm. Apple has embedded Quartz Composer deeply into the operating system. Compositions created in Quartz Composer can be played standalone in any QuickTime-aware application (although only on Mac OS X v10.4), from inside the Quartz Composer application or can be embedded into a Cocoa or Carbon application. Because Quartz Composer makes extensive usage of hardware acceleration and pixel shaders, it is recommended to have a recent graphics card with at least 32MB of VRAM.
Quartz Composer has many similarities to Max/MSP although its primary usage is for graphical rather than audio processing. The ability to construct interactive video compositions that react to audio or MIDI signals but which can be played from any QuickTime aware application has caused a great deal of interest in Quartz Composer from VJs.
Pierre-Olivier Latour originally developed the predecessor to Quartz Composer under the name PixelShox Studio.