Physics.CheckSphere is not working

Question

I try to use Physics.CheckSphere to check if a coordonate is empty. I use three for loop to cycle threw a 2 x Y x 2 chunk. The problem is that it return true if the corner is touching the coordonate

and its actually not even touching it, since I use a 0.5 sphere radius: if(Physics.CheckSphere(new Vector3(x,y,z), 0.5f) == false)...

(by the way the white cubes you can see on the picture is only to visualize where it detected empty space, they dont have any collider enabled)

and the chunks have a mesh collider, so why is it returning true when its no even touching it ?

if(Input.GetKeyDown("i")) {

for(int y = 0; y <= amp + 3; y++)
{
    for(int x = 0; x <= chunkSize - 1; x++)
    {
        for(int z = 0; z <= chunkSize - 1; z++)
        {
            if(Physics.CheckSphere(new Vector3(Mathf.Round(x),Mathf.Round(y),Mathf.Round(z)),0.5f) == false)
            {
                Instantiate(grass,new Vector3(x,y,z), Quaternion.identity);
                dontPlaceHere.Add(new Vector3(x,y,z));
            }
        }
    }
}
}

Answer 1

If you want to stop the 'kissing' from triggering a detection, you'll need to make sure it doesn't kiss.

Use a smaller detection radius. DMGregory points out that 0.49999997f would work.

            if(Physics.CheckSphere(new Vector3(Mathf.Round(x),Mathf.Round(y),Mathf.Round(z)),0.49999997f) == false)