Checking for collision after rotation

Questions & Answers
1

I’m trying to rotate an object, only if the rotated position is collision free. The object is made up of several child objects, each of which have their own collider.

The way I’ve gone about doing this is rotating the object, then checking if the object is in a collision. If it is, the object is rotated back to its original position. However, it seems my collision check is always returning true, so the block is always rotated back. Any ideas? I have a feeling that the children are colliding with each other, which makes the collision check always return true.

I’d also like to note that the collision check works in another part of my code, where I’m checking if a new position is collision-free (without rotation) but doesn’t seem to work here.

Rotation

// block rotation
if (Input.GetKeyDown(KeyCode.Q))
{
    this.transform.Rotate(Vector3(0, 0, 90));
    
    // if rotating puts piece in collision
    if (Collide(this.transform.position.x, this.transform.position.y))
    {
        // rotate back
        this.transform.Rotate(Vector3(0, 0, -90));
    }
}
else if (Input.GetKeyDown(KeyCode.E))
{
    this.transform.Rotate(Vector3(0, 0, -90));
    
    // if rotating puts piece in collision
    if (Collide(this.transform.position.x, this.transform.position.y))
    {
        // rotate back	
        this.transform.Rotate(Vector3(0, 0, 90));
    }
}

Collision Check

// moves peice to specified position and check children for collisions
function Collide(x:Number, y:Number)
{
	// save position
	var oldX:Number = this.transform.position.x;
	var oldY:Number = this.transform.position.y;
	
	// move to new position
	this.transform.position.x = x;
	this.transform.position.y = y;
	
	// make sure none of children collide
	var count:int = this.transform.GetChildCount();
   	for (var i:int = 0; i < count; i++)
   	{
   		var block:Block = this.transform.GetChild(i).GetComponent("Block") as Block;
   		if (block.Collide(block.transform.position.x, block.transform.position.y))
   		{
   			// move back to original pos
   			this.transform.position.x = oldX;
   			this.transform.position.y = oldY;
   		
   			return true;
   		}
   	}
   	
   	// move back to original pos
   	this.transform.position.x = oldX;
   	this.transform.position.y = oldY;
   	
   	return false;
}

Block Collision Check

// checks for collisions at the specified position
function Collide(x:Number, y:Number)
{
	return Physics.CheckSphere(new Vector3(x, y, this.transform.position.z), 0.48);
}
2

Yes, it’s likely that the children are triggering collisions with each other, if there is overlap between their colliders.

There are two ways to solve this I can think of:

The first way is to use the physics layers so that when the children collide with each other, they don’t trigger a collision event. It’s very simple to do following this unity guide: Unity - Manual: Layer-based collision detection

The second way would be to check that the parent is not the same in the collision handling event, and if it is, do nothing.

void OnTriggerEnter(Collider other) {
	if (other.transform.parent == this.transform.parent) {
		return;
	}

	// revert the rotation here
}