Crash when possessing pawn

Development Programming & Scripting
1

Hello, I have created a character using C++. The code written is for VR. It has basic movement feature and also grab certain objects. Then I tried, using blueprint, to possess a pawn.

106171-controller1.png
106171-controller1.png1118×339 54.9 KB

106172-controller2.png
106172-controller2.png1142×482 122 KB

But for some reason it crashes. If I run the same code but instead of possessing from my VRCharacter I posses from some other pawn, then possession is successful. Why does that happen? What can be the possible reasons for it? Any suggestion would be helpful. If code is needed I can provide that too.

Regards

2

Did you check with an “IsValid” Node if the Character you try to possess is actually, well, valid?

3

Tested it with “IsValid” on your suggestion. Still crashing.

4

Could you try to give the Target-input on your Possess node the output of GetPlayerController?

5

the code is in Controller class. Do you want me to try it in this class or move the code to GameMode?

6

Hey,

Can you post the crash log?

Thanks.

7

Here it is:-

MachineId:0A5724804E422E69B5DD0FA03D52BB7B
EpicAccountId:542acf2ff56347d3b52f5c554f92ed63

Access violation - code c0000005 (first/second chance not available)

[rest attached as text][link text][1]
8

That’s OK. In the future you can upload the .txt files instead of pasting the text in them, if you want.

Can you post the following function:

AVRCharacter::MoveForward()
9

Hey,

Can you post the following function?

AVRCharacter::MoveForward()

Thanks

10

Well you were right on spot. I recreated the class again. Added parts of code to see where error is.

void ATestForPossession::MoveForward(float Value)
{
	/*FVector Direction = FRotationMatrix(Controller->GetControlRotation()).GetScaledAxis(EAxis::X);
	AddMovementInput(Direction, Value);*/
}

void ATestForPossession::MoveRight(float Value)
{
	/*FVector Direction = FRotationMatrix(Controller->GetControlRotation()).GetScaledAxis(EAxis::Y);
	AddMovementInput(Direction, Value);*/
}

MoveForward and Move Right are creating the problem. Though I am unable to understand why.

Edit: I commented them because those lines are what were crashing the engine when possessing.

11

Hey,

Can you try this?

 void ATestForPossession::MoveForward(float Value)
 {
	if( Controller )
	{
		FVector Direction = FRotationMatrix( Controller->GetControlRotation( ) ).GetScaledAxis( EAxis::X );
		AddMovementInput( Direction, Value );
	}
 }
 
 void ATestForPossession::MoveRight(float Value)
 {
	if( Controller )
	{
		FVector Direction = FRotationMatrix( Controller->GetControlRotation( ) ).GetScaledAxis( EAxis::Y );
		AddMovementInput( Direction, Value );
	}
 }

Also, to explain what is going on:

You are trying to use “Controller” when it might not exist, resulting in a Access Violation; in “easy” terms, a Access Violation is when the program during runtime tries to use a nullptr (a pointer with an empty value). When this happens, the program will terminate with the error you are getting.

In the future, I recommend checking to make sure any pointer you are using that may not be assigned yet or may lose an assignment. As such:

if( MyPointer )
{
    // Pointer Exists
}
else
{
    // Pointer doesnt exist
}
12

Oh wow thanks a lot. And I feel kinda stupid :P. I messed up at a very basic level. Guess that’s what you get for not programming for a while. This has been a good lesson.

13

As an alternative, the way input is done for most generic characters, is as follows:

[.h]

void Forward( float Amount );
void Right( float Amount );

[cpp]

void MyCharacter::Forward( float Amount )
{
	if( Amount != 0.f )
	{
		AddMovementInput( GetActorForwardVector( ), Amount );
	}
}

void MyCharacter::Right( float Amount )
{
	if( Amount != 0.f )
	{
		AddMovementInput( GetActorRightVector( ), Amount );
	}
}

Good luck with your project.