How do I arc a rigidbody so it lands on a target?

[system]

I have a cannon (the source) point, the projectile (a cannonball) and a target. How do I call the cannonball’s rigidbody so it lands exactly on the target? I want the trajectory to be an arc shape. This is in 3D space (that is, it’s not a 2D platformer like all the other similar questions seem to be asking about).

[Julien-Lynge]

First of all, if you want to spend money and exert minimum effort the free iTween package for Unity has an example project that does pretty much exactly what you’re looking for ( iTween for Unity by Bob Berkebile (pixelplacement) ). The package of examples costs $20, so you may not want to go that route.

If you wanted to do it numerically / with realistic physics, you’d have to solve a few of basic physics equations. You have two variables that describe the motion: the initial velocity and the firing angle. Wikipedia has a great section on the parabolic equation you would need:

Trajectory

In a nutshell, you plug in your desired velocity or angle and range to get the required angle or velocity to hit your target. Then, turn on gravity for the rigidbody and set the initial velocity of the rigidbody. Assuming we’re firing in the positive X direction:

rigidbody.velocity = new Vector3(desiredVel * Mathf.Cos(desiredAngle), desiredVel * Mathf.Sin(desiredAngle), 0f);

In any other direction the Y velocity is the same and you change the X and Z trigonometrically based on your angle around the Y axis.

If you wanted friction from the air this becomes a differential equation, and you should consult your local mathematician.

[aldonaletto]

I answered a similar question some time ago - the cannon shoot at 45 degrees and the ball always land on the target position (unless the target runs away before). Clike here to read this answer.