Resolved Diagonal sine wave movement

I'm making a 2D game and want to spawn some enemies or obstacles who move in a diagonal sine motion. So far I have tried one parametric approach with a parameter t and a rotation matrix. The result isn't working as intended. The intended path is the image below:

Code (CSharp):

1. public class MoveSin_AngledTransform : MonoBehaviour
2. {
3.     float sinCenterY;
4.     public float amplitude;
5.     public float frequency;
6.     private float angle; //rotation of the wave
7.     private float t;
8.    
9.     void Start()
10.     {
11.         t = 0;
12.         sinCenterY = transform.position.y;
13.     }
14.    
15.     public void setAngle(float newAngle) {
16.         angle = newAngle*(Mathf.PI/180);
17.     }
18.    
19.     Vector3 transformcoords(float x_0, float alpha) {
20.         float x = x_0;
21.         float y = Mathf.Sin(x);
22.        
23.         float x_prime = x*Mathf.Cos(alpha) - y*Mathf.Sin(alpha);
24.         float y_prime = x*Mathf.Sin(alpha) + y*Mathf.Cos(alpha);
25.        
26.         Debug.Log("Vector3(x_prime,y_prime,0)= " + x_prime+ ", "+y_prime);
27.         return new Vector3(x_prime,y_prime,0);
28.     }
29.    
30.     void FixedUpdate() {
31.         Vector2 pos = transform.position;
32.        
33.         float sin = Mathf.Sin(pos.x * frequency) * amplitude;
34.         pos.y = sinCenterY + sin;
35.        
36.         t+=Time.deltaTime*180*Mathf.PI; //parameter is an angle in polar coordinates
37.         Vector3 transform_coords = transformcoords(t, angle);
38.        
39.         transform.position = transform_coords;
40.     }
41.  
42.     }
43. }

The sine movement is referenced from this video. This was asked in another question but I am not trying to use an animation/controller like the answer suggests.

How can I move the object as intended? Do I need to not use FixedUpdate()? Should I use Vector3.Lerp? Help is kindly appreciated.

 

Mathf.Sin() will absolutely work 100% of the time and it cares NOTHING about FixedUpdate() or anything else.

It takes a

float

and it gives a

float

.

The input is in radians (not degrees) and it emits -1 to +1 values.

Beyond that, to use Mathf.Sin your only options are:

- change the rate of change of the input (eg, multiply by scale)
- change the phase of the input (skew it forward / backwards in time without changing scale)
- scale the output
- offset the output

 

Thanks for the reply.

Am I correct in assuming my code doesn't work as intended because I am inputting polar coordinates and expecting to map the result to a Cartesian plane?

In that case, it doesn't seem like I can get the diagonal sine result just by using a Lerp with the same transformation.

 

Can you go with different (and easier) approach where you attach that object to a parent which is rotated and moves in a linear path and the child just goes up/down localy with some easing curve?

 

I have continued this here, any assistance would be greatly appreciated: Question - Moving objects in a diagonal sine wave trajectory - Unity Forum