Don't use Alpha Channels in Unreal Engine 5 

Texture samples are one of the most expensive things in a shader, that is why they pack them. Every situation is unique, so a dev needs to look at the given situation to determine best methods of optimization

in short: we dont need masks(A) the same resolution as the RGB texture, we cannot scale it down when its in alpha channel, because it scales RGB aswell, so we separate A from RGBA. Also not to forget, a separate texture is easier to reuse, so basicall you save a lot in the long run too. Thanks!

Its very old knowledge that the alpha channel doubles your memory cost, its not an Unreal thing, it the bit depth - however people often still take this over the extra sample cost However this is more important the more samples you have. If you have a very basic shader as this, the extra sample does not matter You should also pack your most detail requiring in the alpha and the green channel as they have the highest bit depth

Trading extra texture lookup which is one of the slowest operations for memory usage

Just would like to add, If yoy have a black and white mask, you could also use the compression R8 to just use one channel (Red) to pack it. That will also save memory. Also if you use the reduction settings from texture preview (not the max size but the mip map bias) you can use different methods to sharpen or blur the result.

also, one can pack 3 different opacity maps that belong to 3 different assets into one RGB texture, to further optimize the texture memory cost. ideal way of doing that would be to choose 3 assets that are usually used together in the scenes and pack them tohetger, i assume.

Alpha channels are actually great, you just need to put there things that need better accuracy, not simple things like masks... Also, don't look the unreal so called "shader complexity". It's a nonsense metric. Sadly it's hard to explain this to artists and designers. First - the instructions that UE show are not real hardware instructions, and second - different instructions have vastly different cost. Sampling from different textures is costly, this is why we pack textures for PBR for example. Instruction to copy one color to another color is extremely cheap. Of course, sometimes you are running out of memory, and must do tricks, like decreasing the resolution of the alpha channel. But this is optimization depending on the situation you have. I would say, it's much better optimization to not use 4K textures in the first place, since it's required in very specific cases. Definitely not the case you are showing... I'm not sure why artists dig into these complex optimization topics they do not have the know-how, but somehow they are missing the simple optimization to just use the correct texture size, and not have everything 4K...

1. Use BC7 compresion for 4channel data 2. Use texture without gradient with default compresion if you want binary mask then it compreses better with dtx becouse alpha is 1bit 3. please change the title to be less missleading you're miss informing people.

Very helpful video! Thanks for sharing.

Super helpful. Do you have any insights on when to use 16 bit Textures? (RG)

Nice, thanks, I'm about to watch every video you made :D

This is also true in Unreal 4.26. For many situations, alpha masks are included for neatness sake and ease of use, not performance.

Alpha channels are typically 3 channels. So it isn't "RGBA" it's "RRGGBB" or "RGBRGB". Just use a scalar (black and white) mask instead whenever possible.

U miss compression setting. It determines the amount of memory after compression. All textures in the video uses dxt1 / 5 (default), but for different types of textures you need to use different compression options

excellent video

can recommend a texture size for detail normals?

dont listen to this advice. Do a standard texture packing, RMA / ORM + alpha, even if you need to cut your texture mem size for lower specs, you wont notice huge difference cutting the roughness/ metallic and AO textures really. Most imortant is ALBEDO and normal map in PBR workflow for your overall juice. Texture samples are more expensive than you think. There is another reason why you shouldnt use Alpha channels when you dont need to, because of the texture compression settings / algorythm. Without alha channel your textures would be compressed much more.

Cickbait title. :/

Its 2024, you don't need to do this, this is like - 6 years ago. Drawcalls are the most important thing in Games, also - pack the map. This video is misinformation at its highest - It's nearly 2025, electric cars, ai, nvidia chips - somehow people are still optimizing meshes in an era of Nanite and Lumen and adding separate lighting maps. If you are in a professional studio and I see you do this - you're getting "The Talk" that could potentially affect your employment, stay current - pack the map with the alpha, and move on.