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Understanding Texture Formats for iOS: PVRTC 4bit RGBA VS. 16bit RGBA
I see all over the place that 4bit PVRTC is preferable to 16 bit, but 16 bit uses less vram and texture size is significantly smaller by MB.
EDITED TO ADD: Yet in the inspector window the memory goes down (as expected), while stats go up? It's kind of confusing... is the unity stats window broken?
Is there a hidden way 4bit PVRTC is better on iOS, as in stats I see no obvious advantage.
Is the compression of PVRTC format better for speed rendering or something like that it is just better to use if possible?
Answer by DamienSturdy · Apr 19, 2012 at 10:42 AM
When developing for iOS I have found the in-editor stats to be very inaccurate, with massive effort put into reducing the size according to the editor, actually increasing size in game.
PVRTC will only work if you use a ^2 texture (256x256, 512x512, 1024x1024 etc) - If the texture does not fit this requirement it will not be compressed and will use more memory.
Ignoring PVRTC for a second, something else I found out at the same time as this is that if your texture is 1024x513, and you set it's type to GUI, it will, according to the editor, use less memory than a 1024x1024 texture, but on the iphone, this texture will be upsized to 1024x1024- meaning the amount of memory being used on the phone is significantly more than what is recorded in editor.
Hope these help- It cought me out for a few months and almost caused our project major issues. It was a passing comment by the project leader that accidentally hit the nail on the head with the above- You are better off using power of two for every texture, than selecting GUI or Advanced with no Pow2.
Another example- I managed to shave several MB off my game's memory usage because I split the side panel into three pieces of 256x256 instead of one piece of 768x768 (it upscaled to 1024x1024 in the latter instance).
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