Ue4/ue5 illusory engine, material chapter, texture, compression and memory compression and memory

Preface ：

● The reason why we perform compression is , Because memory and bandwidth are limited , Therefore, it must be compressed .
You can't keep everything uncompressed , Especially in very large projects , This is very difficult to do .
obviously , Texture resolution will affect memory and bandwidth without affecting rendering performance .
● If there is a problem with the number and size of textures you use , Then it will affect bandwidth and memory , May cause delays 、 Freeze and jam , But it will not cause frame rate loss .

●  Low frame rate is generally not due to texture problems , If there is a problem with the texture , Then you will see that the displayed texture resolution is very low .
● Lower than the resolution when you import , You will see the delay 、 Phenomena like freezing and Caton , But there will be no low frame rate . This is how we can distinguish possible performance problems .
If any of these problems occur , Usually related to loading , Usually related to texture .

● If you don't use much memory , Then just unzip all the textures in the project .
Especially if your project is not a game , And you can control the hardware , Then such a solution is acceptable .
If it's a game , Then disabling compression will almost certainly not solve the problem , Only in extreme special cases where uncompressed textures have to be used , To disable compression .

One 、 Compression type
BC（Block Compression） Express “ Block compression ” .
DXTC(DirectX Texture comporession） Express “DirectX Texture compression ”.

Two 、DXTC5 Compress  

Transparent channels are hardly compressed ,DXTC5 Indicates compressed red 、 Green and blue and contain transparency ,
But it won't really compress transparency . The transparent file size is the same as that of other channels .

3、 ... and 、BC5 Compress
BC Compression and DXTC The problem with compression is , It is actually very difficult to accurately deal with the color combinations of normal maps .
It cannot mix different colors according to the normal map , To compress the normal map , This is a weakness in the system .

if necessary 100% Uncompressed normal map , Please set it to “ Vector displacement mapping ”, This is a universally applicable compression .
It does nothing , Just import as is .

Four 、TextureStats Texture statistics （Window window ——>Statistics statistics ）

TextureStats Texture statistics , All textures currently in memory in the editor will be displayed . These textures are not necessarily the same as those in the game , When running a project , This is the texture included in the editor . The editor tends to load more textures , Including unnecessary textures .

source ：

https://dev.epicgames.com/community/learning/courses/2dy/materials-master-learning/Y0q/compression-and-memory