Thanks jean, thanks for the method.
Why the raycast rather than proximityTrigger, i don't know. It s for a mobile game. So i ask for 1 frame, for a specific location (crossy road like) ! it looks likes less expansive ..but i never verify.
In other case, when my player hold touch, the character pre-Anim. When player release , the character jump forward. But if there is an obstacle, the pre-anim roll back, and you stay at the same position.
So my need was to check in front of him (or side depending the requested direction) before jumping.
Raycast is usefull for that.
It's possible to offset a trigger to check that.. but... that's seems not elegant solution.