Accurate Mouse Snap to Grid within Threshold? (Float Rounding Errors)

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Im having the same issue as this guy but the convo ended short with no solutions. (http://forum.unity3d.com/threads/snap-to-grid-and-mouse-position.155132/).

I know I need to add a threshold so my mouse can stay within a grid scale of 1 but not sure how to programmably approach it.

could just fix this issue by making the mouse hidden, but Id really like to see how this can be done in a proper way.* I really like the challenge but Ive spent about a day just thinking this through and Im baffled.

I dont know how to explain it further but maybe this image will help. Basically I want the mouse to hover over the entire (1 unit scale) grid. Im aware the behavior is due to rounding of Floats to Ints and that I would need a threshold to "clamp" the mouse to a 1x1 scale grid.

         Ray mouseray = Camera.main.ScreenPointToRay(Input.mousePosition) ;
         Vector3 mousevector3 = new Vector3 (mouseray.origin.x, mouseray.origin.y, mouseray.origin.z);
 
         //apply grid to mouse hover
         if (Physics.Raycast (mouseray.origin, mouseray.direction, out projectorOrigin, 100)) {
             //snap to grid 1x1
             Vector3 gridpos = new Vector3(Mathf.Floor (projectorOrigin.point.x), Mathf.Floor (projectorOrigin.point.y), Mathf.Floor (projectorOrigin.point.z));
             grid.transform.position = new Vector3 (gridpos.x, gridpos.y, gridpos.z);
         }

Demonstration:

alt text

***Notice how my mouse only moves within the UpperRight of the main box of the actual grid.

Answer 1

Best Answer

Answer by adriandevera · Jun 29, 2015 at 03:52 PM

Solved it.

Rather than Mathf.Round use a function such as this. Make sure to add the variable snapValue!

     private float snapValue = 1; //in my case

     private float Round( float input )
     {
         return snapValue * Mathf.Round( ( input / snapValue ) );
     }

Result:

alt text

Sigh, I always solve my issues 10min after I post on here..

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Gorlog · Aug 08, 2016 at 02:52 PM 0

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can u post full code here pls i have a same problem ?

Gorlog · Aug 08, 2016 at 02:56 PM 0

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can u post full code here ? im stuck on same problem

Balddog123 Gorlog · Oct 14, 2020 at 06:58 PM 0

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 using UnityEngine;
 
 public class Follow$$anonymous$$ouse : $$anonymous$$onoBehaviour
 {
     public float snapValue = 20;
 
     // Update is called once per frame
     void Update()
     {
         RaycastHit hit;
         Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
         if(Physics.Raycast(ray, out hit, $$anonymous$$athf.Infinity, 1 << Layer$$anonymous$$ask.NameToLayer("Tile")))
         {
             Vector3 mousePoint = hit.point;
 
             mousePoint.y = 0f;
             mousePoint.x = Round(mousePoint.x);
             mousePoint.z = Round(mousePoint.z);
 
             transform.position = mousePoint;
         }
         
     }
 
     private float Round(float input)
     {
         return snapValue * $$anonymous$$athf.Round(input / snapValue);
     }
 }

Balddog123 Balddog123 · Oct 14, 2020 at 07:00 PM 0

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This is what I did. Raycast to the world from my mouse position. I'm using Adrian's code to round out the X and Z values of the hit.point from my raycast. Then I set the transform.position to the rounded out Vector3.

Accurate Mouse Snap to Grid within Threshold? (Float Rounding Errors)

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