Calculate force needed to reach certain point (AddForce)

Question

Hello everyone, So I have the following system setup for an arrow shooting game:

A force (from 0 to a certain maximum value) is chosen by the player. Say force is F.
The angle (from 0 to 90) is also chosen by the player. Say degrees are D.
Afterwards, having the force and degrees, AddForce is used. Two forces are applied - one for X, and one for Y. F_Y is calculated like this: F * (D / 90f), and F_X = F - F_Y. Thus the force added is AddForce(F_X, F_Y)
The Arrow is fired. Gravity value is default. Arrows may have different weights (rigidbody). Distance between the starting position and end position are given.

I need a way to figure out the total force or just one of the forces needed to reach a SPECIFIC point (X and Y, Z axis is not used at all). I am aware that there are multiple X & Y possibilities, however, is there a way to know at least one of the forces (or the total) having only the following variables? (I need to find out this value in a script for different degree, distance and arrow weight values)

Thank you!

Answer 1

Answer by sysmaya · Jul 04, 2017 at 11:12 PM

This function calculate the Vector3 and speed for parabolic shoots. EJ: Shoot Bows, Shoot canons, etc.

     Vector3 calcBallisticVelocityVector(Vector3 source, Vector3 target, float angle){
         Vector3 direction = target - source;                            
         float h = direction.y;                                           
         direction.y = 0;                                               
         float distance = direction.magnitude;                           
         float a = angle * Mathf.Deg2Rad;                                
         direction.y = distance * Mathf.Tan(a);                            
         distance += h/Mathf.Tan(a);                                      
 
         // calculate velocity
         float velocity = Mathf.Sqrt(distance * Physics.gravity.magnitude / Mathf.Sin(2*a));
         return velocity * direction.normalized;    
     }

Add comment · Show 5 · Share

Serinx · May 28, 2018 at 03:32 AM 0

Share

Hello, Sorry to Necro the thread. Does this factor in the mass of the object being launched? Or is it assumed the mass is 1?

nextage575 · Dec 13, 2019 at 06:16 AM 0

Share

@sysmaya How to call this function?

puppeteer · Mar 21, 2020 at 01:32 PM 0

Share

Thanks, this helped me get the correct bounce direction of a ball to reach a point.

JMEJAY · Jul 07, 2020 at 10:50 PM 0

Share

Hey, any idea how to calculate this considering the drag of the rigidbody?

endasil_unity · Jul 23, 2020 at 08:14 AM 1

Share

Can you explain how the math works here? Why is direction.y distance * Tan(a)? why is h/Tan(a) added to distance? Basically the stuff from that point would be great if you could explain how it works.

Calculate force needed to reach certain point (AddForce)

1 Reply

Your answer

Follow this Question

Related Questions