Tilemap painting in Unity - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Tilemap painting code?

Consider this Unity C# script snippet that paints tiles on a Tilemap. What will be the color of the tile at position (1, 1) after running this code?

Unity

using UnityEngine;
using UnityEngine.Tilemaps;

public class PaintTiles : MonoBehaviour {
    public Tilemap tilemap;
    public TileBase tile;

    void Start() {
        Vector3Int pos = new Vector3Int(1, 1, 0);
        tilemap.SetTile(pos, tile);
        tilemap.SetColor(pos, Color.red);
        tilemap.SetColor(new Vector3Int(0, 0, 0), Color.blue);
    }
}

A The tile at (1,1) is transparent (no color).

B The tile at (1,1) is red.

C The tile at (1,1) has the default color (white).

D The tile at (1,1) is blue.

💡 Hint

Remember that SetColor changes the color of the tile at the specified position.

The code sets the tile at (1,1) and then colors it red. The blue color is applied to a different tile at (0,0), so (1,1) remains red.

🧠 Conceptual

intermediate

Which method paints a tile on a Tilemap in Unity?

In Unity's Tilemap system, which method is used to place a tile at a specific grid position?

A tilemap.SetTile(Vector3Int position, TileBase tile)

B tilemap.PlaceTile(Vector3Int position, TileBase tile)

C tilemap.AddTile(Vector3Int position, TileBase tile)

D tilemap.PaintTile(Vector3Int position, TileBase tile)

💡 Hint

Look for the official Unity Tilemap API method that sets a tile.

The correct method to place a tile on a Tilemap is SetTile. Other methods do not exist in the API.

🔧 Debug

advanced

Why does this Tilemap painting code not show the tile?

Look at this code snippet. Why does the tile not appear on the Tilemap after running?

Unity

using UnityEngine;
using UnityEngine.Tilemaps;

public class PaintTiles : MonoBehaviour {
    public Tilemap tilemap;
    public TileBase tile;

    void Start() {
        Vector3 pos = new Vector3(2, 2, 0);
        tilemap.SetTile(Vector3Int.FloorToInt(pos), tile);
    }
}

A Vector3Int.FloorToInt(pos) is invalid and causes a runtime error.

B Using Vector3 instead of Vector3Int causes the tile not to appear.

C The tile variable is not assigned, so no tile is painted.

D Tilemap.SetTile requires a Vector3 position, not Vector3Int.

💡 Hint

Check if the tile variable has a value before painting.

If the tile variable is null (not assigned in the inspector), SetTile will not paint anything visible.

📝 Syntax

advanced

Which option correctly paints multiple tiles in a loop?

Which code snippet correctly paints tiles at positions (0,0), (1,0), and (2,0) on a Tilemap?

A for (int x = 0; x < 3; x++) { tilemap.SetTile(new Vector3Int(x, 0, 0), tile); }

B for (int x = 0; x < 3; x++) { tilemap.SetTile(new Vector3(x, 0, 0), tile); }

C for (int x = 0; x < 3; x++) { tilemap.SetTile(new Vector2Int(x, 0), tile); }

D for (int x = 0; x < 3; x++) { tilemap.SetTile(new Vector2(x, 0), tile); }

💡 Hint

Tilemap.SetTile requires a Vector3Int position.

SetTile expects a Vector3Int for the position. Option A uses Vector3Int correctly. Option A uses Vector3 which is invalid. Options C and D use Vector2Int and Vector2 which are not accepted.

🚀 Application

expert

How many tiles are painted after this code runs?

Given this code, how many tiles will be painted on the Tilemap?

Unity

using UnityEngine;
using UnityEngine.Tilemaps;

public class PaintTiles : MonoBehaviour {
    public Tilemap tilemap;
    public TileBase tile;

    void Start() {
        for (int x = 0; x < 3; x++) {
            for (int y = 0; y < 3; y++) {
                if ((x + y) % 2 == 0) {
                    tilemap.SetTile(new Vector3Int(x, y, 0), tile);
                }
            }
        }
    }
}

A 9 tiles

B 6 tiles

C 4 tiles

D 5 tiles

💡 Hint

Count how many (x,y) pairs from 0 to 2 satisfy (x + y) % 2 == 0.

The pairs where (x + y) is even are: (0,0), (0,2), (1,1), (2,0), (2,2). That's 5 tiles painted.

Practice

1. What does the SetTile method do in Unity's Tilemap painting?

easy

A. It resizes the tilemap grid.

B. It changes the color of the entire tilemap.

C. It places or removes a tile at a specific grid position.

D. It saves the tilemap as an image file.

Solution

1. Step 1: Understand the purpose of SetTile

   The SetTile method is used to place or remove tiles at specific positions on the tilemap grid.

2. Step 2: Compare with other options

   Changing color, resizing grid, or saving as image are not functions of SetTile.

3. Final Answer:

   It places or removes a tile at a specific grid position. -> Option C

4. Quick Check:

   SetTile = Place or remove tile [OK]

Hint: Remember SetTile changes tiles at grid spots [OK]

Common Mistakes:

• Thinking SetTile changes tilemap color
• Confusing SetTile with resizing grid
• Assuming SetTile exports images

2. Which of the following is the correct syntax to set a tile at position (2, 3) on a Tilemap named tilemap using a tile named myTile?

easy

A. tilemap.SetTile(new Vector2(2, 3), myTile);

B. tilemap.SetTile(2, 3, myTile);

C. tilemap.SetTile(Vector3(2, 3), myTile);

D. tilemap.SetTile(new Vector3Int(2, 3, 0), myTile);

Solution

1. Step 1: Identify correct parameter types for SetTile

   The SetTile method requires a Vector3Int for grid position and a tile object.

2. Step 2: Check each option's syntax

   tilemap.SetTile(new Vector3Int(2, 3, 0), myTile); uses new Vector3Int(2, 3, 0) which is correct. Options A, B, and D use wrong types or missing 'new' keyword.

3. Final Answer:

   tilemap.SetTile(new Vector3Int(2, 3, 0), myTile); -> Option D

4. Quick Check:

   SetTile needs Vector3Int position [OK]

Hint: Use Vector3Int for tile positions in SetTile [OK]

Common Mistakes:

• Using Vector2 instead of Vector3Int
• Omitting 'new' keyword for Vector3Int
• Passing separate x,y instead of Vector3Int

3. Given the code below, what will be the output on the tilemap?

Vector3Int pos = new Vector3Int(1, 1, 0);
tilemap.SetTile(pos, myTile);
tilemap.SetTile(pos, null);

medium

A. The tile at position (1,1) will be removed (empty).

B. The tile at position (1,1) will be set to myTile.

C. An error occurs because the same position is set twice.

D. The tilemap will have two tiles at position (1,1).

Solution

1. Step 1: Understand SetTile behavior with null

   Setting a tile to null removes the tile at that position.

2. Step 2: Analyze the code sequence

   First, the tile at (1,1) is set to myTile. Then it is immediately removed by setting it to null.

3. Final Answer:

   The tile at position (1,1) will be removed (empty). -> Option A

4. Quick Check:

   SetTile with null removes tile [OK]

Hint: SetTile with null clears tile at position [OK]

Common Mistakes:

• Thinking setting twice causes error
• Assuming tile remains after setting null
• Believing multiple tiles can stack at one position

4. What is wrong with this code snippet that tries to paint a tile?

Vector3Int position = new Vector3Int(0, 0, 0);
tilemap.SetTile(position, myTile);
position = new Vector3Int(1, 0);
tilemap.SetTile(position, myTile);

medium

A. SetTile cannot be called twice in a row.

B. The second Vector3Int is missing the z coordinate.

C. The variable 'position' cannot be reassigned.

D. myTile is not defined before use.

Solution

1. Step 1: Check Vector3Int constructor usage

   The first Vector3Int has three coordinates (x, y, z). The second only has two, which is invalid.

2. Step 2: Understand Vector3Int requirements

   Vector3Int requires three integer arguments; missing the z coordinate causes a compile error.

3. Final Answer:

   The second Vector3Int is missing the z coordinate. -> Option B

4. Quick Check:

   Vector3Int needs 3 ints [OK]

Hint: Always provide x, y, and z for Vector3Int [OK]

Common Mistakes:

• Assuming Vector3Int can have 2 parameters
• Thinking SetTile calls cause errors
• Believing variables can't be reassigned

5. You want to paint a 3x3 square of tiles starting at position (0,0) on a Tilemap named tilemap using a tile named grassTile. Which code snippet correctly does this?

hard

A. for (int x = 0; x < 3; x++) {
for (int y = 0; y < 3; y++) {
tilemap.SetTile(new Vector3Int(x, y, 0), grassTile);
}
}

B. for (int i = 0; i < 9; i++) {
tilemap.SetTile(new Vector3Int(i, i, 0), grassTile);
}

C. tilemap.SetTile(new Vector3Int(0, 0, 0), grassTile);
tilemap.SetTile(new Vector3Int(1, 1, 0), grassTile);
tilemap.SetTile(new Vector3Int(2, 2, 0), grassTile);

D. tilemap.SetTile(new Vector3Int(0, 0, 0), grassTile);
tilemap.SetTile(new Vector3Int(0, 1, 0), grassTile);
tilemap.SetTile(new Vector3Int(0, 2, 0), grassTile);

Solution

1. Step 1: Understand the goal to paint a 3x3 square

   We need to paint tiles at all positions where x and y range from 0 to 2.

2. Step 2: Analyze each code snippet

   for (int x = 0; x < 3; x++) { for (int y = 0; y < 3; y++) { tilemap.SetTile(new Vector3Int(x, y, 0), grassTile); } } uses nested loops for x and y from 0 to 2, correctly covering all 9 positions. for (int i = 0; i < 9; i++) { tilemap.SetTile(new Vector3Int(i, i, 0), grassTile); } paints diagonal only. tilemap.SetTile(new Vector3Int(0, 0, 0), grassTile); tilemap.SetTile(new Vector3Int(1, 1, 0), grassTile); tilemap.SetTile(new Vector3Int(2, 2, 0), grassTile); paints only three diagonal tiles. tilemap.SetTile(new Vector3Int(0, 0, 0), grassTile); tilemap.SetTile(new Vector3Int(0, 1, 0), grassTile); tilemap.SetTile(new Vector3Int(0, 2, 0), grassTile); paints only one column.

3. Final Answer:

   for (int x = 0; x < 3; x++) { for (int y = 0; y < 3; y++) { tilemap.SetTile(new Vector3Int(x, y, 0), grassTile); } } -> Option A

4. Quick Check:

   Nested loops cover 3x3 grid [OK]

Hint: Use nested loops for grid painting [OK]

Common Mistakes:

• Painting only diagonal tiles
• Painting fewer tiles than needed
• Using single loop for 2D grid