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swifttexturesmetal

ASTC Texture compression in metal– what should I use as the bytes per row?

I'm writing a program that's using compressed textures in Metal. I'm having a bit of trouble with the replaceRegion() function of MTLTexture. The parameter bytesPerRow just doesn't seem to make sense. It says that for compressed textures, "bytesPerRow is the number of bytes from the beginning of one row of blocks to the beginning of the next."

Now I'm using ASTC with 4x4 blocks, which means that I have 8 bpp. So then 4*4 is 16, and 8 bits is one byte. So I'm guessing that each block size is 16 bytes. But yet, when I enter 16, I get a failed assertion that requires the minimum value to be 4096. What's going on?

Thank you very much.

Solution

  • bytesPerRow = texelsPerRow / blockFootprint.x * 16