It's exactly what I mentioned. Smaller images may have some page sub-allocation strategy. Small buffers in Metal are sub-allocated from a larger 128K buffer, but that's harder with texture data. Not that on macOS Intel, the page size is higher so the need to atlas is even more true there.
256x256, mips 8, Astc: 21872, Metal: 32768 <- mips add up to 16K x 4/3 approx = 21845, but due to align and 16K page size, padded out to 32K
256x256, mips 1, Astc: 16384, Metal: 16384 <- this is the exact fit 32x32x16B = 16K
Topic:
Graphics & Games
SubTopic:
Metal
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