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.