AST-TEX-001: Texture Health

What This Rule Detects

This rule flags textures with one or more of these issues:

• Over budget: Maximum dimension exceeds threshold (default: 4096 pixels)
• Non-power-of-two: Dimensions aren’t powers of 2 (128, 256, 512, 1024, etc.)
• Missing mipmaps: No mip chain for runtime textures
• Compression issues: Uncompressed or using editor-only compression

Why This Matters

Memory Math (Deterministic)

Texture memory follows deterministic formulas you can calculate exactly:

Uncompressed RGBA8 (4 bytes/pixel):

Mipmap overhead: A full mip chain adds approximately 33% to base memory. A 4K texture with mipmaps uses ~85 MB instead of ~64 MB—but this is a worthwhile trade for reduced bandwidth and aliasing.

Compression Ratios (Hardware Facts)

BC formats compress fixed 4×4 pixel blocks:

A 4K BC1 texture uses ~8 MB instead of ~64 MB uncompressed—8× savings.

Why Mipmaps Matter

Mipmaps reduce bandwidth and aliasing at distance:

• Bandwidth: Lower mips fetch fewer bytes per sample
• Cache efficiency: Mip selection puts hot data in cache
• Visual stability: Prevents shimmer/moiré at distance

Platform documentation (Apple, Android, console TRCs) explicitly describes mipmaps as reducing bandwidth and improving sampling performance while reducing aliasing artifacts.

Real Example: A project with 200 textures at 4K instead of 2K wastes ~10 GB of memory. Downscaling appropriately can halve package size and dramatically improve load times.

How to Verify

1. Select texture in Content Browser
2. Open Size Map (right-click → Asset Actions → Size Map)
3. Check the Statistics panel in Texture Editor
4. Use stat Memory in PIE to see runtime texture pool usage

When This Is Acceptable

• Hero textures: Key character faces, marketing materials, or signature assets where maximum quality is required
• UI textures: Some UI elements legitimately need non-power-of-two dimensions (though consider using UserInterface compression)
• Intentional settings: Textures with specific compression requirements for technical reasons (normal maps, masks, etc.)

The Problem

Issue 1: Oversized Textures

T_Hero_Diffuse.uasset
├── Imported size: 8192 x 8192   ← Way over budget
├── Actual visible detail: 2K equivalent
└── Memory cost: ~256 MB (vs ~16 MB at 2K)

Just because your source texture is 8K doesn’t mean the game needs 8K. Evaluate actual viewing distances and detail requirements.

Issue 2: Non-Power-of-Two Dimensions

T_Background_Pattern.uasset
├── Size: 1920 x 1080           ← NPOT dimensions
├── Can't use BC compression efficiently
├── May cause GPU cache issues
└── Streaming system works less efficiently

Power-of-two dimensions (256, 512, 1024, 2048, 4096) allow hardware compression, efficient mipmapping, and optimal memory alignment.

Issue 3: Missing Mipmaps

T_Floor_Tile.uasset
├── Size: 2048 x 2048
├── Mip levels: 1               ← No mipmap chain
├── At distance: samples full 2K for 10 pixels on screen
└── Causes aliasing shimmer and wasted bandwidth

Without mipmaps, the GPU samples the full texture even when the object is far away, wasting bandwidth and causing visual artifacts.

Issue 4: Uncompressed/Editor-Only Compression

T_Character_Normal.uasset
├── Compression: None           ← No compression
├── Memory: 64 MB
├── With BC5: ~16 MB
└── Visual difference: minimal

Uncompressed textures take 4-8x more memory than compressed equivalents with minimal visual difference for most use cases.

The Fix

Option 1: Set Appropriate Maximum Size

In Texture Editor → Details:

1. Set Maximum Texture Size to match your actual needs
2. Common targets:
   • Characters/Props: 2048
   • Environment: 1024-2048
   • UI: 512-1024
   • Effects: 256-512

The engine will downscale on import while preserving the source file for future re-imports.

Option 2: Fix Non-Power-of-Two Dimensions

Best: Re-export source texture at power-of-two dimensions:

• 1920 x 1080 → 2048 x 1024 (or 2048 x 2048)
• 1000 x 1000 → 1024 x 1024

Alternative: Enable Power of Two Mode in texture settings:

• “Pad to Power of Two” adds black borders
• “Stretch to Power of Two” stretches content

For UI textures, non-power-of-two is often acceptable—use UserInterface2D compression.

Option 3: Enable Mipmaps

In Texture Editor → Details → Level of Detail:

1. Set Mip Gen Settings to FromTextureGroup or SimpleAverage
2. Verify Never Stream is disabled (unless intentional)
3. Check the texture preview shows multiple mip levels

When to skip mipmaps:

• UI textures that are always viewed at exact size
• Lookup tables (LUTs) and data textures
• Textures smaller than 64x64

Option 4: Choose Correct Compression

In Texture Editor → Details → Compression:

1. Set Compression Settings to appropriate type
2. Disable sRGB for non-color data (normals, masks, roughness)
3. Verify Compress Without Alpha if alpha channel is unused

Configuration

Threshold: Maximum texture dimension (default: 4096 pixels)

To adjust in Project Settings:

Blueprint Health Analyzer → Rule Thresholds → AST-TEX-001 → 2048.0

Lower thresholds (2048) are appropriate for mobile or projects prioritizing memory. Higher thresholds (8192) may be acceptable for high-end PC projects.

Related Rules

• AST-UNUSED-001 - Unused textures wasting disk space
• MAT-TEX-001 - Materials sampling too many textures
• AST-MESH-001 - Mesh optimization issues