Model 3 3D Hardware
Main Tree Node (a.k.a Scene Descriptor) description

Index |	Description

  0	Bits 8 - 11: Viewport selection (only 0 - 3, 2 bits ?)
	Bits 3 - 4: Viewport priority

  1	Sub tree node link
  2	Next main tree link
  3	Unknown
  4	Sun Light Vector Z component
  5	Sun Light Vector Y component
  6	Sun Light Vector X component
  7	Sun Light Intensity (floating point)
  8	Unknown
  9	Unknown
  10	Unknown
  11	Unknown
  12	Unknown
  13	Unknown
  14	Unknown
  15	Unknown
  16	Unknown
  17	Unknown
  18	Unknown
  19	Unknown

  20	High word: Viewport Y width (14.2 fixed point ?)
	Low word:  Viewport X width

  21	Unknown
  22	Matrix base address
  23	Unknown
  24	Unknown
  25	Unknown

  26	High word: Viewport Y start (12.4 fixed point ?)
	Low word:  Viewport X start

  27	Bits 8 - 11: Viewport Selection (why is this in two places ?)
	Bits 3 - 4: Viewport Priority

  28	Unknown

  29	High word: Light Y size
	Low word:  Light Ypos (13.3 fixed point ?)

  30	High word: Light X size
	Low word:  Light Xpos

  31	Light extent (floating point)

  32	Byte 3 (highest / first byte): Unknown
	Byte 2: Unknown
	Byte 1: Unknown
	Byte 0: Scroll Fog (0.8 fixed point ?)

  33	Unknown
  34	Fog Color
  35	Fog Density (floating point)

  36	Byte 3 (highest / first byte): Unknown
	Byte 2: Unknown
	Byte 1: Sun Light Ambient (0.8 fixed point ?)
	Byte 0: Scroll Attenuation (0.8 fixed point ?)

  37	Fog Offset
  38	Unknown
  39	Unknown
  40	Unknown
  41	Unknown
  42	Unknown
  43	Unknown
  44	Unknown
  45	Unknown
  46	Unknown
  47	Unknown