AThe ambient coefficient is an attribute of type kQ3AttributeTypeAmbientCoefficient. It is a floating point value between 0.0 and 1.0 that determines how much of a scene's ambient light is reflected from an object's surface. It's described on page 5-15 of the unabridged version of 3D Graphics Programming with QuickDraw 3D, which you can find as an Adobe Acrobat file on the CD-ROM that accompanies the book in: QuickDraw 3D Documentation/QuickDraw 3D Reference/3D Graphics Prog w/ QD3D .