Tilemap basics in Unity - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Tilemap cell position code?

Consider this Unity C# code snippet that gets the cell position of a world point in a Tilemap:

Vector3 worldPos = new Vector3(2.5f, 3.7f, 0f);
Vector3Int cellPos = tilemap.WorldToCell(worldPos);
Debug.Log(cellPos);

What will be printed in the console?

Unity

Vector3 worldPos = new Vector3(2.5f, 3.7f, 0f);
Vector3Int cellPos = tilemap.WorldToCell(worldPos);
Debug.Log(cellPos);

A (2, 3, 0)

B (3, 4, 0)

C (2, 4, 0)

D (3, 3, 0)

💡 Hint

Remember that WorldToCell rounds down to the nearest cell coordinates.

The WorldToCell method converts a world position to the cell position by flooring the x and y values. So 2.5 becomes 2 and 3.7 becomes 3.

❓ Predict Output

intermediate

What does this code print when setting a tile?

Given a Tilemap and a TileBase tile, what will this code print?

Vector3Int pos = new Vector3Int(1, 1, 0);
tilemap.SetTile(pos, tile);
TileBase result = tilemap.GetTile(pos);
Debug.Log(result == tile);

Unity

Vector3Int pos = new Vector3Int(1, 1, 0);
tilemap.SetTile(pos, tile);
TileBase result = tilemap.GetTile(pos);
Debug.Log(result == tile);

A True

B False

C NullReferenceException

D Compilation error

💡 Hint

SetTile assigns the tile at the position, GetTile returns the tile at that position.

After setting the tile at position (1,1,0), GetTile returns the same tile object, so the comparison is true.

🔧 Debug

advanced

Why does this Tilemap code throw a NullReferenceException?

Look at this code snippet:

Tilemap tilemap;
void Start() {
    Vector3Int pos = new Vector3Int(0, 0, 0);
    TileBase tile = tilemap.GetTile(pos);
    Debug.Log(tile.name);
}

Why does this code throw a NullReferenceException?

Unity

Tilemap tilemap;
void Start() {
    Vector3Int pos = new Vector3Int(0, 0, 0);
    TileBase tile = tilemap.GetTile(pos);
    Debug.Log(tile.name);
}

A pos is invalid and causes GetTile to fail

B tilemap is not assigned and is null, so calling GetTile causes the exception

C tile is null because no tile exists at pos, so accessing tile.name causes the exception

D Debug.Log cannot print tile.name because TileBase has no name property

💡 Hint

Check if the tile exists at the position before accessing its properties.

If no tile exists at the given position, GetTile returns null. Accessing tile.name then causes a NullReferenceException.

🧠 Conceptual

advanced

How does the Tilemap's origin affect tile placement?

In Unity Tilemaps, what happens if you change the Tilemap's origin property?

A The origin changes the size of each tile in the Tilemap

B The origin determines the sorting order of tiles when rendered

C The origin sets the default tile used when no tile is placed

D The origin shifts the coordinate system, so tile positions are offset accordingly

💡 Hint

Think about how coordinates relate to tile positions.

The origin shifts the coordinate system of the Tilemap, so all tile positions are offset by the origin value.

❓ Predict Output

expert

What is the number of tiles after this code runs?

Consider this code that sets tiles in a Tilemap:

for (int x = 0; x < 3; x++) {
    for (int y = 0; y < 3; y++) {
        Vector3Int pos = new Vector3Int(x, y, 0);
        if ((x + y) % 2 == 0) {
            tilemap.SetTile(pos, tile);
        }
    }
}
int count = 0;
foreach (var pos in tilemap.cellBounds.allPositionsWithin) {
    if (tilemap.GetTile(pos) != null) count++;
}
Debug.Log(count);

What number will be printed?

Unity

for (int x = 0; x < 3; x++) {
    for (int y = 0; y < 3; y++) {
        Vector3Int pos = new Vector3Int(x, y, 0);
        if ((x + y) % 2 == 0) {
            tilemap.SetTile(pos, tile);
        }
    }
}
int count = 0;
foreach (var pos in tilemap.cellBounds.allPositionsWithin) {
    if (tilemap.GetTile(pos) != null) count++;
}
Debug.Log(count);

A 4

B 5

C 9

D 6

💡 Hint

Count how many positions satisfy (x + y) % 2 == 0 in a 3x3 grid.

Positions where (x + y) is even are (0,0), (0,2), (1,1), (2,0), (2,2) — total 5 tiles set.

Practice

1. What is the main purpose of a Tilemap in Unity?

easy

A. To manage 3D models and animations

B. To optimize network communication

C. To handle player input events

D. To create 2D game worlds using a grid of tiles

Solution

1. Step 1: Understand Tilemap functionality

   Tilemaps are used to build 2D game worlds by arranging tiles on a grid.

2. Step 2: Compare options with Tilemap purpose

   Only To create 2D game worlds using a grid of tiles describes creating 2D worlds with tiles, matching Tilemap's role.

3. Final Answer:

   To create 2D game worlds using a grid of tiles -> Option D

4. Quick Check:

   Tilemap = 2D grid of tiles [OK]

Hint: Tilemaps = 2D grids for game worlds [OK]

Common Mistakes:

• Confusing Tilemap with 3D model management
• Thinking Tilemap handles input or networking

2. Which of the following is the correct way to place a tile at position (2, 3) on a Tilemap named 'tilemap' in Unity C#?

easy

A. tilemap.SetTile(new Vector3Int(2, 3, 0), tile);

B. tilemap.SetTile(new Vector2(2, 3), tile);

C. tilemap.PlaceTile(2, 3, tile);

D. tilemap.AddTile(new Vector3(2, 3, 0), tile);

Solution

1. Step 1: Recall Tilemap SetTile method signature

   SetTile requires a Vector3Int for grid position and a TileBase object.

2. Step 2: Check each option's method and parameters

   tilemap.SetTile(new Vector3Int(2, 3, 0), tile); uses SetTile with Vector3Int(2,3,0), which is correct. Others use wrong methods or Vector2.

3. Final Answer:

   tilemap.SetTile(new Vector3Int(2, 3, 0), tile); -> Option A

4. Quick Check:

   SetTile(Vector3Int, TileBase) = correct syntax [OK]

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

Common Mistakes:

• Using Vector2 instead of Vector3Int for position
• Using non-existent methods like PlaceTile or AddTile

3. What will be the result of this code snippet in Unity?

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

medium

A. Tiles placed at positions (0,0), (0,1), (1,0), (1,1), (2,0), (2,1)

B. Tiles placed only at (0,0) and (1,1)

C. Tiles placed at positions (0,0), (1,0), (2,0) only

D. No tiles placed due to syntax error

Solution

1. Step 1: Analyze the nested loops and tile positions

   The outer loop runs x from 0 to 2 (3 times), inner loop runs y from 0 to 1 (2 times). Each iteration places a tile at (x,y).

2. Step 2: List all tile positions placed

   Positions: (0,0), (0,1), (1,0), (1,1), (2,0), (2,1).

3. Final Answer:

   Tiles placed at positions (0,0), (0,1), (1,0), (1,1), (2,0), (2,1) -> Option A

4. Quick Check:

   Nested loops fill grid area = positions listed [OK]

Hint: Nested loops fill all grid positions in range [OK]

Common Mistakes:

• Miscounting loop ranges or tile positions
• Assuming only diagonal tiles placed

4. Identify the error in this Unity C# code that tries to fill a 2x2 area with tiles:

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

medium

A. The loops should use < instead of <= to avoid infinite loop

B. The loops run too many times, placing tiles in a 3x3 area instead of 2x2

C. The tilemap variable is not initialized

D. The SetTile method is called with wrong parameters

Solution

1. Step 1: Check loop conditions and iterations

   Loops use <= 2, so x and y go from 0 to 2 inclusive, which is 3 iterations each.

2. Step 2: Calculate total tiles placed

   3 x 3 = 9 tiles placed, which is a 3x3 area, not 2x2.

3. Final Answer:

   The loops run too many times, placing tiles in a 3x3 area instead of 2x2 -> Option B

4. Quick Check:

   Loop <= 2 means 3 iterations, not 2 [OK]

Hint: Use < for loop limits to match area size [OK]

Common Mistakes:

• Using <= instead of < causing extra iterations
• Assuming loops run only 2 times when they run 3

5. You want to create a checkerboard pattern on a 4x4 Tilemap grid using two tiles: tileA and tileB. Which code snippet correctly sets tiles so that adjacent tiles alternate between tileA and tileB?

hard

A. for (int x = 0; x < 4; x++) {
for (int y = 0; y < 4; y++) {
tilemap.SetTile(new Vector3Int(x, y, 0), y % 2 == 0 ? tileA : tileB);
}
}

B. for (int x = 0; x < 4; x++) {
for (int y = 0; y < 4; y++) {
tilemap.SetTile(new Vector3Int(x, y, 0), x % 2 == 0 ? tileA : tileB);
}
}

C. for (int x = 0; x < 4; x++) {
for (int y = 0; y < 4; y++) {
tilemap.SetTile(new Vector3Int(x, y, 0), (x + y) % 2 == 0 ? tileA : tileB);
}
}

D. for (int x = 0; x < 4; x++) {
for (int y = 0; y < 4; y++) {
tilemap.SetTile(new Vector3Int(x, y, 0), tileA);
}
}

Solution

1. Step 1: Understand checkerboard pattern logic

   Checkerboard alternates tiles so adjacent tiles differ. Using (x + y) % 2 == 0 alternates tiles diagonally and horizontally.

2. Step 2: Evaluate each option's tile assignment

   for (int x = 0; x < 4; x++) { for (int y = 0; y < 4; y++) { tilemap.SetTile(new Vector3Int(x, y, 0), (x + y) % 2 == 0 ? tileA : tileB); } } uses (x + y) % 2 to alternate tileA and tileB correctly. The options using x % 2 or y % 2 alone create stripes by row or column, not checkerboard. for (int x = 0; x < 4; x++) { for (int y = 0; y < 4; y++) { tilemap.SetTile(new Vector3Int(x, y, 0), tileA); } } uses only tileA.

3. Final Answer:

   for (int x = 0; x < 4; x++) { for (int y = 0; y < 4; y++) { tilemap.SetTile(new Vector3Int(x, y, 0), (x + y) % 2 == 0 ? tileA : tileB); } } -> Option C

4. Quick Check:

   Checkerboard = alternate tiles by (x + y) parity [OK]

Hint: Use (x + y) % 2 to alternate tiles in grid [OK]

Common Mistakes:

• Alternating only by x or y, not both
• Using same tile everywhere
• Forgetting to use modulo for pattern