geometric operations

Light Sources

light and area-light specify new light and area light source shaders. name should be a string specifying the name of the shader. Both procedures return a unique integer identifier for the light source which can be used by illuminate to selectively illuminate surfaces. Lights which appear inside separators only illuminate objects within that separator; however, lights are different from all other gops in that they still exist outside that separator (unlike other attribute gops) and can illuminate other surfaces if the illuminate gop is used.

(illuminate id onoff)

illuminate turns a light on or off by specifying the integer identifier of the light source to modify. (This identifier is returned by the light or area-light gops.) onoff is a boolean, #t for "on" and #f for "off."

(light-shadows onoff)

light-shadows is an attribute of the graphics state which specifies whether or not light sources should cast shadows on other objects. If onoff is #t, subsequently created light sources will cast shadows. If onoff is #f, subsequently created light sources will not cast shadows.

(casts-shadows val)

casts-shadows is an attribute of the graphics state which specifies whether or not subsequent geometry will casts shadows on other geometry (when shadow-casting light sources are present). If val is #t, geometry will casts shadows (using a policy defined by the specific renderer). If val is #f, geometry will not casts shadows. val can also be a string in which case it specifies a renderer specific setting. val is #t by default.

(light-camera onoff)

light-camera is an attribute of the graphics state which specifies whether or not a camera for the light source will be created. If onoff is true, subsequently declared light sources will have an associated camera which gives a view of the scene as seen by the light source. This mechanism is frequently used when rendering shadow maps to determine if the shadow map will adequately and efficiently cover the area to be shadowed. onoff is #f by default.