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Question Trying to add 3D object to grid?

Discussion in 'Scripting' started by Deleted User, May 19, 2023.

  1. Deleted User

    Deleted User



    I've been trying to follow this tut.
    This isn't the first time I tried this, I just wasn't ready for it then. However after being a lot more skilled I'm still struggling. Some reason, I can't get the prefabbed object to move on the grid and always appear at the same spot? So much for it being for beginners- as I'm no noob and am still lost on what I'm doing wrong. This tut is old, though, is there a more updated one for this?

    If not, here's my building system:

    Code (CSharp):
    1. using System.Collections;
    2. using System.Collections.Generic;
    3. using UnityEngine;
    4. using UnityEngine.Tilemaps;
    6. public class BuildingSystem : MonoBehaviour
    7. {
    8.     public static BuildingSystem current;
    9.     public GridLayout gridLayout;
    10.     private Grid grid;
    12.     [SerializeField] private Tilemap MainTileMap;
    13.     [SerializeField]private TileBase WhiteTile;
    15.     public GameObject Prefab1;
    17.     private PlaceableObject ObjectToPlace;
    19.     #region UnityMethods
    21.     private void Awake()
    22.     {
    23.         current = this;
    24.         grid = gridLayout.gameObject.GetComponent<Grid>();
    25.     }
    27.     private void Update()
    28.     {
    29.         if (Input.GetKeyDown(KeyCode.A))
    30.         {
    31.             InitializeWidthObject(Prefab1);
    32.         }
    33.     }
    35.     #endregion
    37.     #region Utils
    39.     public static Vector3 GetMouseWorldPosition()
    40.     {
    41.         Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
    42.         if (Physics.Raycast(ray, out RaycastHit rayCastHit))
    43.         {
    44.             return rayCastHit.point;
    45.         }
    46.         else
    47.         {
    48.             return;
    49.         }
    50.     }
    52.     public Vector3 SnapCoordinateToGrid(Vector3 position)
    53.     {
    54.         Vector3Int cellPos = gridLayout.WorldToCell(position);
    55.         position = grid.GetCellCenterWorld(cellPos);
    56.         return position;
    57.     }
    59.     #endregion
    61.     #region Building Placement
    63.     public void InitializeWidthObject(GameObject prefab)
    64.     {
    65.         Vector3 position = SnapCoordinateToGrid(;
    67.         GameObject obj = Instantiate(prefab, position, Quaternion.identity);
    68.         ObjectToPlace = obj.GetComponent<PlaceableObject>();
    69.         obj.AddComponent<ObjectDrag>();
    70.     }
    72.     #endregion
    73. }
    And I also have the object drag.
    Code (CSharp):
    1. using System.Collections;
    2. using System.Collections.Generic;
    3. using UnityEngine;
    5. public class ObjectDrag : MonoBehaviour
    6. {
    7.     private Vector3 offset;
    9.     private void OnMouseDown()
    10.     {
    11.         offset = transform.position - BuildingSystem.GetMouseWorldPosition();
    12.     }
    14.     private void OnMouseDrag()
    15.     {
    16.         Vector3 pos = BuildingSystem.GetMouseWorldPosition() + offset;
    17.         transform.position = BuildingSystem.current.SnapCoordinateToGrid(pos);
    18.     }
    19. }
    This shouldn't be that hard... I'm not into the entire tut yet, just in the part where she says to test things and they should work- but they clearly don't?
  2. Deleted User

    Deleted User


    Screenshot (725).png Screenshot (728).png Screenshot (726).png

    Attached Files:

  3. Kurt-Dekker


    Mar 16, 2013
    If you actually did the tutorial correctly (see below for how!), then it really sounds like it is...

    Time to start debugging! Here is how you can begin your exciting new debugging adventures:

    You must find a way to get the information you need in order to reason about what the problem is.

    Once you understand what the problem is, you may begin to reason about a solution to the problem.

    What is often happening in these cases is one of the following:

    - the code you think is executing is not actually executing at all
    - the code is executing far EARLIER or LATER than you think
    - the code is executing far LESS OFTEN than you think
    - the code is executing far MORE OFTEN than you think
    - the code is executing on another GameObject than you think it is
    - you're getting an error or warning and you haven't noticed it in the console window

    To help gain more insight into your problem, I recommend liberally sprinkling
    statements through your code to display information in realtime.

    Doing this should help you answer these types of questions:

    - is this code even running? which parts are running? how often does it run? what order does it run in?
    - what are the names of the GameObjects or Components involved?
    - what are the values of the variables involved? Are they initialized? Are the values reasonable?
    - are you meeting ALL the requirements to receive callbacks such as triggers / colliders (review the documentation)

    Knowing this information will help you reason about the behavior you are seeing.

    You can also supply a second argument to Debug.Log() and when you click the message, it will highlight the object in scene, such as

    If your problem would benefit from in-scene or in-game visualization, Debug.DrawRay() or Debug.DrawLine() can help you visualize things like rays (used in raycasting) or distances.

    You can also call Debug.Break() to pause the Editor when certain interesting pieces of code run, and then study the scene manually, looking for all the parts, where they are, what scripts are on them, etc.

    You can also call GameObject.CreatePrimitive() to emplace debug-marker-ish objects in the scene at runtime.

    You could also just display various important quantities in UI Text elements to watch them change as you play the game.

    Visit Google for how to see console output from builds. If you are running a mobile device you can also view the console output. Google for how on your particular mobile target, such as this answer or iOS: or this answer for Android:

    If you are working in VR, it might be useful to make your on onscreen log output, or integrate one from the asset store, so you can see what is happening as you operate your software.

    Another useful approach is to temporarily strip out everything besides what is necessary to prove your issue. This can simplify and isolate compounding effects of other items in your scene or prefab.

    Here's an example of putting in a laser-focused Debug.Log() and how that can save you a TON of time wallowing around speculating what might be going wrong:

    "When in doubt, print it out!(tm)" - Kurt Dekker (and many others)

    Note: the
    function is an alias for Debug.Log() provided by the MonoBehaviour class.


    Tutorials and example code are great, but keep this in mind to maximize your success and minimize your frustration:

    How to do tutorials properly, two (2) simple steps to success:

    Step 1. Follow the tutorial and do every single step of the tutorial 100% precisely the way it is shown. Even the slightest deviation (even a single character!) generally ends in disaster. That's how software engineering works. Every step must be taken, every single letter must be spelled, capitalized, punctuated and spaced (or not spaced) properly, literally NOTHING can be omitted or skipped.

    Fortunately this is the easiest part to get right: Be a robot. Don't make any mistakes.

    If you get any errors, learn how to read the error code and fix your error. Google is your friend here. Do NOT continue until you fix your error. Your error will probably be somewhere near the parenthesis numbers (line and character position) in the file. It is almost CERTAINLY your typo causing the error, so look again and fix it.

    Step 2. Go back and work through every part of the tutorial again, and this time explain it to your doggie. See how I am doing that in my avatar picture? If you have no dog, explain it to your house plant. If you are unable to explain any part of it, STOP. DO NOT PROCEED. Now go learn how that part works. Read the documentation on the functions involved. Go back to the tutorial and try to figure out WHY they did that. This is the part that takes a LOT of time when you are new. It might take days or weeks to work through a single 5-minute tutorial. Stick with it. You will learn.

    Step 2 is the part everybody seems to miss. Without Step 2 you are simply a code-typing monkey and outside of the specific tutorial you did, you will be completely lost. If you want to learn, you MUST do Step 2.

    Of course, all this presupposes no errors in the tutorial. For certain tutorial makers (like Unity, Brackeys, Imphenzia, Sebastian Lague) this is usually the case. For some other less-well-known content creators, this is less true. Read the comments on the video: did anyone have issues like you did? If there's an error, you will NEVER be the first guy to find it.

    Beyond that, Step 3, 4, 5 and 6 become easy because you already understand!

    Finally, when you have errors, don't post here... just go fix your errors! Here's how:

    Remember: NOBODY here memorizes error codes. That's not a thing. The error code is absolutely the least useful part of the error. It serves no purpose at all. Forget the error code. Put it out of your mind.

    The complete error message contains everything you need to know to fix the error yourself.

    The important parts of the error message are:

    - the description of the error itself (google this; you are NEVER the first one!)
    - the file it occurred in (critical!)
    - the line number and character position (the two numbers in parentheses)
    - also possibly useful is the stack trace (all the lines of text in the lower console window)

    Always start with the FIRST error in the console window, as sometimes that error causes or compounds some or all of the subsequent errors. Often the error will be immediately prior to the indicated line, so make sure to check there as well.

    Look in the documentation. Every API you attempt to use is probably documented somewhere. Are you using it correctly? Are you spelling it correctly?

    All of that information is in the actual error message and you must pay attention to it. Learn how to identify it instantly so you don't have to stop your progress and fiddle around with the forum.