block placement with raycast in unity3d

Question

I'm trying a game like Space Engineers/Minecraft. with this code, I place a block on the side of a block already placed using raycast. It works well until I add a collider(then it place the block anywhere between block and screen). Help with code or another idea, please.

RaycastHit hit;
int maxBuildDist = 10;
public GameObject Block;
Vector3 BlockPos;

void Update(){

if(Physics.Raycast(Camera.main.ScreenPointToRay(                                                
    new Vector3((Screen.width / 2 ),(Screen.height / 2),0)),out hit, maxBuildDist)){

        BlockPos = new Vector3(hit.normal.x,hit.normal.y,hit.normal.z);  

        Block.transform.position = (hit.transform.position + BlockPos)/2;                         
    }
}

}

Answer 1

Update your Physics.Raycast call to only hit the objects you're interested in. Check the Physics.Raycast documentation about the layerMask parameter to learn how to do this: https://docs.unity3d.com/ScriptReference/Physics.Raycast.html

1. Create a layer, and set on block prefab

Use the dropdown menu in the prefab's Inspector window:

2. Update call to Physics.Raycast

Say you created a new layer named "BlockLayer". You would change your Update function to this:

// Find the layer based on its name.
var layerId = LayerMask.NameToLayer("BlockLayer");

// Set our mask to "ignore everything except for blocks".
var layerMask = ~layerId;

// Update the Physics.Raycast call - pass in the layer mask
if(Physics.Raycast(
  Camera.main.ScreenPointToRay(new Vector3((Screen.width / 2 ),(Screen.height / 2),0)),
  out hit,
  maxBuildDist,
  layerMask))
{
    // This code will only be reached if the raycast hit a block.
    BlockPos = new Vector3(hit.normal.x,hit.normal.y,hit.normal.z);  
    Block.transform.position = (hit.transform.position + BlockPos)/2;                         
}