Converting radians to degrees with C#

Question

I'm creating a small game in Unity with C#, I'm not allowed to use any of the built in physics or colliders. What I have is a platform with a weight object on it. With the arrow keys you can tilt the platforms angle. The weight on top should then react accordingly to the given tilt angle. I have calculated everything with the friction, max friction, normal force a.s.o. The thing that doesn't work is when you press a key to change the tilt, the force on the object should change accordingly, and if the force on the weight is greater that the maximum friction force, then the weight should move. Here is a simplified example of my code.

public float m = 35;

public float µ = 0.15f;

public float g = 9.82f; //(N/kg)

public float N;

public double deg = 0;

Fmax = m * g * µ;

if (Input.GetKeyDown(KeyCode.UpArrow)) {
   deg++;
   N = m * g * µ * (Math.Cos(deg) * (180.0 / Math.PI));
   platform.transform.Rotate(0, 0, deg, Space.Self);

} else if (Input.GetKeyDown(KeyCode.DownArrow)) {
   deg--;
   N = m * g * µ * (Math.Cos(deg) * (180.0 / Math.PI));
   platform.transform.Rotate(0, 0, deg, Space.Self);
}

if(N > Fmax) {
 // Do the rest of the code
}

I think that the problem has to do with that Math.Cos(deg) turns the deg into a radian, but I tried to then covert back the reg to a deg with: (180.0 / Math.PI). I can get everything to work on my calculator but not in the code.

Do you mean rad(ians) to deg(rees)? Unsure what `reg` is. If you do mean radians then Unity has a conversion for that build in in the `Mathf` libary. `Mathf.Rad2Deg` and `Mathf.Deg2Rad` https://docs.unity3d.com/ScriptReference/Mathf.Rad2Deg.html https://docs.unity3d.com/ScriptReference/Mathf.Deg2Rad.html — Remy, Dec 17 '19 at 11:39
You need `Math.Cos(deg * Math.PI / 180)`. Math.Cos takes its argument in radians. — Andrew Morton, Dec 17 '19 at 11:47
I got it working with @AndrewMorton solution but now I get a convert error when I want to do this: ```N = m * g * µ * ((Math.Cos(deg * Math.PI / 180)));``` should I cast it? — Krullmizter, Dec 17 '19 at 12:24
I suggest using only `double` for floating-point numbers. The only thing you will get from `float` is problems in this case. Ref: [Float vs Double Performance](https://stackoverflow.com/a/417591/1115360). — Andrew Morton, Dec 17 '19 at 12:36
@Krullmizter it is exactly the same as already suggested by Remy_rm : `Mathf.Cos(deg * Mathf.Deg2Rad)` since it returns exactly the same as `Math.PI / 180` does. Note that there is a difference between the general c# library `Math` and Unity built-in `Mathf`! — derHugo, Dec 17 '19 at 12:39
Cosine value ranges from -1 to +1. The conversion has to happen so the argument you pass to the function is in radians. It would go inside the function argument, not multiplying the cosine value. — duffymo, Dec 17 '19 at 15:06
Unsolicited advice: I'd avoid namimg a variable `µ`. There's potential for that to cause issues. It's also just more difficult to type. I'd go with `mu` or `u`. — 3Dave, Dec 17 '19 at 15:13

score 3 · Accepted Answer · answered Dec 17 '19 at 15:07

3

This is incorrect:

   N = m * g * µ * (Math.Cos(deg) * (180.0 / Math.PI));

If the angle is in degrees you have to convert it to radians and pass that the cosine function:

double rad = deg*Math.PI/180.0;
N = m*g*mu*Math.Cos(rad);

answered Dec 17 '19 at 15:07

duffymo

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This still not part of the Math/MathF classes? Wtf... – jjxtra Mar 26 '23 at 17:13
I don't know of a single language that uses degrees instead of radians as inputs to trig functions. Not one, from FORTRAN to C to Java to Python. – duffymo Mar 26 '23 at 17:18
I mean that Math/MathF don't have a built in DegreesToRadians function. – jjxtra Mar 26 '23 at 17:51
It's a one-liner. How hard is it? – duffymo Mar 27 '23 at 00:47
Not hard. More just annoying to have to add it to every project. – jjxtra Mar 27 '23 at 14:38
You're living a fine life if this is your biggest annoyance. – duffymo Mar 27 '23 at 14:44
I can't complain I suppose. – jjxtra Mar 27 '23 at 14:45

score 1 · Answer 2 · answered Dec 17 '19 at 16:17

You can easily convert from radians to degrees and from degrees to radians using the Mathf.Deg2Rad and Mathf.Rad2Deg constants

using UnityEngine;

public class Example : MonoBehaviour
{
    // convert 1 radian to degrees

    float rad = 10.0f;

    void Start()
    {
        float deg = rad * Mathf.Rad2Deg;
        Debug.Log(rad + " radians are equal to " + deg + " degrees.");
    }
}

score -1 · Answer 3 · answered Dec 18 '19 at 02:47

-1

There is a super handy function called Mathf.Rad2Deg and Mathf.Deg2Rad. They convert radians to degrees and degrees to radians.

answered Dec 18 '19 at 02:47

ninety-ninehundred

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Those aren't functions, they are fields. – Ruzihm Jan 09 '20 at 23:44

Converting radians to degrees with C#

3 Answers3