CODEWITHSUNDEEP
c#unity-game-engine
Andrew
Andrew

Reputation: 367

Unity Ridgidbody Constraints, Freeze Position Y

I want to freeze the y position of a block in Unity. Here is my C# code:

var test = GetComponent<Rigidbody>().constraints;
test = RigidbodyConstraints.FreezePositionY;

It comes up with no errors however the Y position doesn't freeze.

Could someone help me? I have read the documentation but it just says to do what I have done.

Upvotes: 0

Views: 6677

Answers (1)

Maximilian Gerhardt
Maximilian Gerhardt

Reputation: 5353

RigidbodyConstaints is an enumeration (enum, mind that small word in the doc), you must change it directly without making a copy of it first. With that code, you're pulling a copy of that enum, then modify it, that's why it this fails:

using UnityEngine;
using System.Collections;

public class PosFreezer : MonoBehaviour {

    void Start () {
        var rb = GetComponent<Rigidbody>();
        var constr = rb.constraints; //grab a copy (NOT a reference)
        constr = RigidbodyConstraints.FreezePositionY; //(modify the copy)
    }
}

This does not:

using UnityEngine;
using System.Collections;

public class PosFreezer : MonoBehaviour {

    void Start () {
        var rb = GetComponent<Rigidbody>();
        //Modify the constraints directly.
        rb.constraints = RigidbodyConstraints.FreezePositionY;
    }
}

So, remember, every enum is a value type, like a struct, in comparison to an instance of a class, which is a reference type. Grabbing a copy of a value type and modifying it localy probably doesn't do what you want. Your code would however also have worked if you had written:

var test = GetComponent<Rigidbody>().constraints;
test = RigidbodyConstraints.FreezePositionY;
GetComponent<Rigidbody>().constraints = test;

But that's to messy and unreadable anyways.

Upvotes: 1

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