Strategy to implement NPCs "visibility"

Hi. 

On the AI of my game, the NPCs (non-player character)  must be able to "see" the player.

>From the eye position, the player it´s visible if he/she it´s inside a pyramid or cone with a, say, 60 degrees.

It´s possible to use ODE to implement this?

Other way it´s to cast a ray from the eye to the player, and if it doesn´t collide with anything, the player it´s visible.

I would like to use ODE as the only collision system.

Thanks


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