I'm trying to make a character jump on a landing pad who stays above him. Here is the formula I've used (everything is pretty much self-explainable, maybe except character_MaxForce that is the total force the character can jump ):

deltaPosition = target - character_position;
sqrtTerm = Sqrt(2*-gravity.y * deltaPosition.y + MaxYVelocity* character_MaxForce);
time = (MaxYVelocity-sqrtTerm) /gravity.y;
speedSq = jumpVelocity.x* jumpVelocity.x + jumpVelocity.z *jumpVelocity.z;

if speedSq < (character_MaxForce * character_MaxForce) we have the right time so we can store the value

jumpVelocity.x = deltaPosition.x / time;
jumpVelocity.z = deltaPosition.z / time;

otherwise we try the other solution

time = (MaxYVelocity+sqrtTerm) /gravity.y; 

and then store it

jumpVelocity.x = deltaPosition.x / time;
jumpVelocity.z = deltaPosition.z / time;
jumpVelocity.y = MaxYVelocity;

rigidbody_velocity = jumpVelocity;

The problem is that the character is jumping away from the landing pad or sometime he jumps too far never hitting the landing pad.