Sets a floating point attribute.
int rc;
/* set the world's directional light source to point straight down */
aw_float_set (AW_WORLD_LIGHT_X, 0.0f);
aw_float_set (AW_WORLD_LIGHT_Y, -1.0f);
aw_float_set (AW_WORLD_LIGHT_Z, 0.0f);
if (rc = aw_world_attributes_changes ())
printf ("Unable to change world attributes (reason %d)\n", rc);