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Why a 0.2mb texture becomes a 12mb texture when imported?

Hi all,

I wanted to try a new way to improve my VRAM usage, so I decided to make texture compression outside Unreal, and importing them into Unreal when they are very light.

Surprisingly, if I imported the original PNG image into Unreal, it finally weights the same than importing a very light JPG image into the engine.

For this experiment, I used a 23mb PNG image and a 250kb one. When they are imported into Unreal, one is consuming 24.5mb and the other one is taking 5.3mb (but not sure if it’s only disk usage, or VRAM usage). When exported from Unreal to my PC, as TGA, they are (both of them) 12mb.

When applied as a material, both image quality is almost the same, with a huuuuuuge size improvement, even if it doesn’t care for Unreal (I think). I understand UE makes its own texture compression but, if it notices a texture is much more lighter without compressing, it shouldn’t try to compress it at all, isn’t it?. Or maybe I’m missing something…

PS: and what about calling the textures of the Master material too, even if the only used material is a material instance which has overwritten the original textures placed into the Material’s Graph? (Again, I’m not sure if this is only a Disk issue, or maybe VRAM too).

Here you are the testing project and the original textures too: https://mega.nz/file/iBEzzAYI#-hanvh…kiKYA047r5FjiY

Thank you ans best regards!

Game engines have to use specific types of compression, which is largely based on the resolution of the image, so if you’ve got a 1024x1024 texture that you’ve compressed to a very small .jpg file it’ll end up as the same size as any other 1024x1024 file when brought in the game engine. In the editor you can change the compression though and choose an option that you like better than the default, and certain textures should certainly have their compression settings changed. For example if it’s black and white then you don’t need a compression format designed for an RGB texture, you just need one with a single channel.
Also, textures get saved with mipmaps, which are lower resolution versions of the texture that it can switch between based on your game quality settings, but that ultimately means that one texture file will get bigger since it has some smaller versions of it saved along with it. You can turn that option off as well if you’d like.