In this lesson, you will learn how to configure and leverage mipmap chains to maintain high-speed visual fidelity while drastically reducing GPU cache thrashing.
The Problem: Cache Misses and Aliasing
When a high-resolution 4K texture is mapped to an object occupying only a few pixels on screen, the GPU must skip over massive amounts of data to sample the texels. This results in cache thrashing (because the texture data doesn't fit in the L1/L2 cache) and aliasing artifacts (shimmering edges due to sub-pixel sampling). Mipmap chains solve this by pre-computing lower-resolution versions of your texture. When the object is far away, the engine swaps to a smaller mip level, ensuring the sampled data is local and cache-friendly.
Configuring Mip Generation
In Unreal Engine, mipmap generation is controlled within the Texture Editor. For most assets, you should ensure Mip Gen Settings is set to FromTextureGroup. This allows the engine to apply specific filtering algorithms (like Sharpen or Blur) based on the asset's role in the game.
To optimize for high-speed camera movement, you should strictly avoid NoMipmaps unless absolutely necessary (e.g., UI elements). If you notice shimmering during rapid motion, adjust the Mip Gen Settings to Sharpen or explicitly use an Advanced setting to control the bias.
Fine-Tuning with Mip Bias
You can influence the mipmap selection via the Mip Gen Settings or by adjusting the Texture LOD Bias in the material graph. If a texture appears blurry at mid-range, you may be tempted to increase the resolution; however, the correct approach for performance is to ensure the Texture Streaming Pool is budgeted correctly.
For high-speed movement, consider using the following optimization approach in your DefaultEngine.ini:
[TextureStreaming]
PoolSizeVRAM=4000
; Ensure Mipmaps are prioritized for fast-moving objects
LimitPoolSizeToVRAM=True
By ensuring these chains exist, the GPU spends fewer cycles calculating texel averages on the fly and more time pushing pixels, keeping your frame times consistent even during complex camera pans.
Key Takeaway: Mipmap chains are essential for cache coherency; by providing the GPU with pre-filtered, down-sampled texture data, you eliminate aliasing and prevent memory bandwidth bottlenecks during high-speed motion.