Tilemap painting in Unity - Performance & Optimization

Performance: Tilemap painting

MEDIUM IMPACT

Tilemap painting affects rendering speed and frame rate by controlling how many tiles are drawn and how often the GPU updates the screen.

Updating many tiles individually every frame

Unity

var tileChanges = new List<TileChange>(); foreach (var tile in tilesToUpdate) { tileChanges.Add(new TileChange(tile.position, tile.newTile)); } tilemap.SetTiles(tileChanges);

Batching tile updates reduces draw calls and GPU uploads to a single operation.

📈 Performance Gainsingle draw call and GPU upload per batch, reducing frame rendering time

Updating many tiles individually every frame

Unity

foreach (var tile in tilesToUpdate) { tilemap.SetTile(tile.position, tile.newTile); }

This triggers multiple separate draw calls and reuploads to the GPU, causing slow rendering.

📉 Performance Costtriggers N draw calls and GPU uploads per frame, where N is number of tiles updated

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Individual tile updates per frame	Many tile set calls	N reflows (conceptual redraws)	High GPU paint cost	[X] Bad
Batch tile updates	Single batch set call	1 reflow	Low GPU paint cost	[OK] Good

Rendering Pipeline

Tilemap painting updates the GPU texture atlas and triggers the GPU to redraw the affected tiles on screen.

→Layout

→Paint

→Composite

⚠️ BottleneckPaint stage is most expensive due to GPU texture updates and draw calls.

Optimization Tips

1Batch tile updates to minimize GPU draw calls.

2Avoid updating tiles every frame unless necessary.

3Use Unity Profiler to monitor draw calls and GPU usage.

Performance Quiz - 3 Questions

What is the main performance cost when updating many tiles individually every frame?

A Multiple GPU draw calls and texture uploads

B Increased CPU memory usage

C Slower physics calculations

D Longer script compilation time

DevTools: Unity Profiler

How to check: Open Unity Profiler, record while updating tiles, check Rendering and GPU usage sections.

What to look for: Look for high draw call counts and GPU upload spikes indicating inefficient tile updates.

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