anistrophy - turning on?

[sketchbook]

how do you get the anistrophy section under specular to turn on? i need to use it but am not sure what setting gets it from being greyed out.

thanks!

[machmirdenlukas]

how do you get the anistrophy section under specular to turn on? i need to use it but am not sure what setting gets it from being greyed out.

thanks!

just use specular-type blinn or ward instead of phong.
cheers m