| Type | Name | Surface | Displ. | Purpose |
| color | Cs | R | -- | Surface color (input) |
| color | Os | R | -- | Surface opacity (input) |
| point | P | R | RW | Surface position |
| point | dPdu | R | R | Change in position with u |
| point | dPdv | R | R | Change in position with v |
| point | N | R | RW | Surface shading normal |
| point | Ng | R | R | Surface geometric normal |
| float | u,v | R | R | Surface parameters |
| float | du,dv | R | R | Change in u,v across element |
| float | s,t | R | R | Surface texture coordinates |
| color | L | R | -- | Direction from surface to light source |
| color | Cl | R | -- | Light color |
| point | I | R | -- | Direction of ray intersecting on surface point |
| color | Ci | RW | -- | Color of light from surface (output) |
| color | Oi | RW | -- | Opacity of surface (output) |
| point | E | R | -- | Position of camera |