# How to make the SGI logo

Written by Paul Bourke
November 1992

The SGI logo is generated as follows:
Given two lengths l1 and l2, the "turtle graphics" instructions along with the resulting wire frame result are given below. In what follows, left and right refer to moving towards the negative numbers or positive numbers respectively. Up and down is movement along the z axis, back and forward refer to the y axis.

 forward l1 left l2 down l1 right l1 up l2 back l1 down l1 forward l2 left l1 back l1 right l2 up l1 left l1 down l2 forward l1 up l1 back l2 right l1

In the example above l1 = 1 and l2 = 0.7

Turning the line segments into cylinder/sphere pairs is shown below with its geometric description in Radiance

 s cylinder cyl 0 0 7 -0.5 -0.5 0.5 0.5 -0.5 0.5 0.13 s cylinder cyl 0 0 7 0.5 -0.5 0.5 0.5 0.5 0.5 0.13 s cylinder cyl 0 0 7 -0.2 -0.8 -0.8 -0.2 0.2 -0.8 0.13 s cylinder cyl 0 0 7 -0.2 0.2 -0.8 0.8 0.2 -0.8 0.13 s cylinder cyl 0 0 7 0.8 0.2 -0.8 0.8 -0.5 -0.8 0.13 s cylinder cyl 0 0 7 0.8 -0.5 -0.8 0.8 -0.5 0.2 0.13 s cylinder cyl 0 0 7 0.8 -0.5 0.2 0.8 0.5 0.2 0.13 s cylinder cyl 0 0 7 0.8 0.5 0.2 0.8 0.5 -0.5 0.13 s cylinder cyl 0 0 7 0.8 0.5 -0.5 -0.2 0.5 -0.5 0.13 s cylinder cyl 0 0 7 -0.2 0.5 -0.5 -0.2 0.5 0.5 0.13 s cylinder cyl 0 0 7 0.5 0.5 0.5 -0.2 0.5 0.5 0.13 s cylinder cyl 0 0 7 -0.5 -0.5 0.5 -0.5 0.2 0.5 0.13 s cylinder cyl 0 0 7 -0.5 0.2 0.5 -0.5 0.2 -0.5 0.13 s cylinder cyl 0 0 7 -0.5 0.2 -0.5 -0.5 -0.8 -0.5 0.13 s cylinder cyl 0 0 7 -0.5 -0.8 -0.5 -0.5 -0.8 0.2 0.13 s cylinder cyl 0 0 7 -0.5 -0.8 0.2 0.5 -0.8 0.2 0.13 s cylinder cyl 0 0 7 0.5 -0.8 0.2 0.5 -0.8 -0.8 0.13 s cylinder cyl 0 0 7 0.5 -0.8 -0.8 -0.2 -0.8 -0.8 0.13 s sphere sph 0 0 4 -0.5 -0.5 0.5 0.13 s sphere sph 0 0 4 0.5 -0.5 0.5 0.13 s sphere sph 0 0 4 0.5 0.5 0.5 0.13 s sphere sph 0 0 4 -0.2 0.2 -0.8 0.13 s sphere sph 0 0 4 0.8 0.2 -0.8 0.13 s sphere sph 0 0 4 0.8 -0.5 -0.8 0.13 s sphere sph 0 0 4 0.8 -0.5 0.2 0.13 s sphere sph 0 0 4 0.8 0.5 0.2 0.13 s sphere sph 0 0 4 0.8 0.5 -0.5 0.13 s sphere sph 0 0 4 -0.2 0.5 -0.5 0.13 s sphere sph 0 0 4 -0.2 0.5 0.5 0.13 s sphere sph 0 0 4 -0.2 0.5 0.5 0.13 s sphere sph 0 0 4 -0.5 0.2 0.5 0.13 s sphere sph 0 0 4 -0.5 0.2 -0.5 0.13 s sphere sph 0 0 4 -0.5 -0.8 -0.5 0.13 s sphere sph 0 0 4 -0.5 -0.8 0.2 0.13 s sphere sph 0 0 4 0.5 -0.8 0.2 0.13 s sphere sph 0 0 4 0.5 -0.8 -0.8 0.13 s sphere sph 0 0 4 -0.2 -0.8 -0.8 0.13

The "logo" can be interlinked in each 3D direction, a few cells are shown below