I can't fix the error cannot convert from 'float' to 'UnityEngine.Vector3'

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Arms : MonoBehaviour
{
int speed = 300;
public Rigidbody2D rb;
public Camera cam;
public KeyCode mousebutton;

void Update()
{
Vector3 playerpos = new Vector3(cam.ScreenToWorldPoint(Input.mousePosition).x, cam.ScreenToWorldPoint(Input.mousePosition.y, 0));
Vector3 difference = playerpos - transform.position;
float rotationZ = Mathf.Atan2(difference.x, -difference.y) * Mathf.Rad2Deg;
if (Input.GetKey(mousebutton))
{
rb.MoveRotation(Mathf.LerpAngle(rb.rotation, rotationZ, speed * Time.fixedDeltaTime));
}
}
}

 

You are using Mathf.LerpAngle() for Rigidbody.MoveRotation() that uses Quaternion.
use Quaternion.Slerp() or Quaternion.Lerp() or Quaternion.RotateTowards()
instead.
Beside this your Mathf.LerpAngle() is trying to Lerp between a quaternion (rb.rotation) & a float (rotationZ)... must make a choice...

 

Yes indeed, well put alexeu! And for OP, here is how to understand the choice and make the choice:

Some help to fix "Cannot implicitly convert type 'Xxxxx' into 'Yyyy':"

http://plbm.com/?p=263

If you're just hammering in sample code and have no idea, keep this in mind:

Tutorials and example code are great, but keep this in mind to maximize your success and minimize your frustration:

How to do tutorials properly, two (2) simple steps to success:

Tutorials are a GREAT idea. Tutorials should be used this way:

Step 1. Follow the tutorial and do every single step of the tutorial 100% precisely the way it is shown. Even the slightest deviation (even a single character!) generally ends in disaster. That's how software engineering works. Every step must be taken, every single letter must be spelled, capitalized, punctuated and spaced (or not spaced) properly, literally NOTHING can be omitted or skipped.

Fortunately this is the easiest part to get right: Be a robot. Don't make any mistakes.
BE PERFECT IN EVERYTHING YOU DO HERE!!

If you get any errors, learn how to read the error code and fix your error. Google is your friend here. Do NOT continue until you fix your error. Your error will probably be somewhere near the parenthesis numbers (line and character position) in the file. It is almost CERTAINLY your typo causing the error, so look again and fix it.

Step 2. Go back and work through every part of the tutorial again, and this time explain it to your doggie. See how I am doing that in my avatar picture? If you have no dog, explain it to your house plant. If you are unable to explain any part of it, STOP. DO NOT PROCEED. Now go learn how that part works. Read the documentation on the functions involved. Go back to the tutorial and try to figure out WHY they did that. This is the part that takes a LOT of time when you are new. It might take days or weeks to work through a single 5-minute tutorial. Stick with it. You will learn.

Step 2 is the part everybody seems to miss. Without Step 2 you are simply a code-typing monkey and outside of the specific tutorial you did, you will be completely lost. If you want to learn, you MUST do Step 2.

Of course, all this presupposes no errors in the tutorial. For certain tutorial makers (like Unity, Brackeys, Imphenzia, Sebastian Lague) this is usually the case. For some other less-well-known content creators, this is less true. Read the comments on the video: did anyone have issues like you did? If there's an error, you will NEVER be the first guy to find it.

Beyond that, Step 3, 4, 5 and 6 become easy because you already understand!

Finally, when you have errors...

Remember: NOBODY here memorizes error codes. That's not a thing. The error code is absolutely the least useful part of the error. It serves no purpose at all. Forget the error code. Put it out of your mind.

The complete error message contains everything you need to know to fix the error yourself.

The important parts of the error message are:

- the description of the error itself (google this; you are NEVER the first one!)
- the file it occurred in (critical!)
- the line number and character position (the two numbers in parentheses)
- also possibly useful is the stack trace (all the lines of text in the lower console window)

Always start with the FIRST error in the console window, as sometimes that error causes or compounds some or all of the subsequent errors. Often the error will be immediately prior to the indicated line, so make sure to check there as well.

All of that information is in the actual error message and you must pay attention to it. Learn how to identify it instantly so you don't have to stop your progress and fiddle around with the forum.

 

But where do i have to change something in the script?

 

If you wrote this you would know instantly what you intend to do.

If you copied this, go back because you copied it incorrectly. See my steps above.

If you are sure you copied it properly and it doesn't work, move onto a new tutorial or source of code. There's THOUSANDS of examples of simple stuff out there to learn from.

The purpose of this forum is to assist people who are ready to learn by doing, and who are unafraid to get their hands dirty learning how to code, particularly in the context of Unity3D.

If you just want someone to do it for you, you need go to one of these places:

https://forum.unity.com/forums/commercial-job-offering.49/

https://forum.unity.com/forums/non-commercial-collaboration.17/

 

But as alexu said, i should change the Mathf.LerpAngle() To Quaternion.Lerp() but that gave me another error.

 

Looks like you're using a Quaternion and 2 floats, as was said above. that's what you need to change.

rb.MoveRotation(Mathf.LerpAngle(rb.rotation-->Quaternion, rotationZ-->Float, speed * Time.fixedDeltaTime-->Float));

Quaternion is kinda like a Vector3 in that it has multiple floats involved(xPos, yPos, zPos) vs (xRot, yRot, zRot, w), so you're essentially telling it a rotation(3 transform.rotations and w), float.y, float.z rather than just (rot.x, rot,y, rot.z, w)

"Quaternions can be used to represent the orientation or rotation of a GameObject. This representation internally consists of four numbers (referenced in Unity as x, y, z & w)"

https://docs.unity3d.com/Manual/QuaternionAndEulerRotationsInUnity.html
https://docs.unity3d.com/ScriptReference/Rigidbody-rotation.html

Unity Documentation is your friend, my friend.

 

There's a lot of problems here.

First, OP still has not edited his post and fixed the code formatting, making it harder on EVERYBODY to see what is happening.

Second, Rigidbody2D is used in the original script. That takes a

float

angle, not a Quaternion, for the .rotation field. See the docs.

Thirdly, this tangle:

Code (csharp):

1. Vector3 playerpos = new Vector3(cam.ScreenToWorldPoint(Input.mousePosition).x,
2.        cam.ScreenToWorldPoint(Input.mousePosition.y, 0));

That is COMPLETELY wrong... parenthesis in the wrong place, wrong types arguments, just gibberish as far as the computer is concerned, not to mention needlessly calling an expensive camera transform function twice, which is the least of sins here.

Go back to where you got the above line of code from and as my original post says, work through it until a) you get it correct, and b) you understand it. Do ONE THING PER LINE:

- read the mouse position
- adjust anything about that position (such as the Z.. it matters. Read the docs for world point!)
- get the world point
- do what you need for it.

I quote:

"Combining a bunch of stuff into one line always feels satisfying, but it's always a PITA to debug." - Star Manta on the Unity3D forums