Schecterman opened this issue on Oct 20, 2010 · 31 posts
bagginsbill posted Thu, 21 October 2010 at 10:24 PM
Huh?
"actually" powers of 8?
As in, not really a power of 2? I differ.
4096 is a power of 2, 4, 8, 16, and 64. Which one is the important one?
3000 or 4000 is not chosen because it works better with texture compression, if by that you mean MIP mapping - quite the opposite. MIP stands for the Latin "multum in parvo", i.e. much in a small space. When a texture is MIP mapped, multiple reduced resolutions are pre-calculated by dividing the resolution in half repeatedly. So the "most" even or best size is one that results in a perfect division by 2 repeatedly all the way down to 1 pixel.
Which means that the best size is precisely a power of 2. If it happens to also be a power of something else, such as 4, 8, 16, 32, etc, that is because the power of 2 is not prime and can be decomposed, not because it is actually better.
4096 is 2 ^ 12. This can also be written as, for example, 2 ^ (4 * 3), which is (2^4) ^ 3, which is 16 ^ 3. It is also 2 ^ (6 * 2), AKA (2^6) ^2, AKA 64 ^2.
The size 2048 is 2 ^ 11. This cannot be decomposed, because 11 is prime, and so it is not also a power of 4 or 8. But it is a great size for MIP mapping a texture.
4096->2048->1024->512->256->128->64->32->16->8->4->2->1
4000->2000->1000->500->250->125->uhoh
However, all is not lost. In reality, the 4000 pixel texture is first extended to 4096 with black or junk. Then the MIP mapping is applied. However, this can lead to seams when using a tiled texture.
But we're talking about skin textures, where seams have nothing to do with what is at the edge of the texture image. It has to do with whether or not the person making the texture understands how MIP mapping averages pixels in a neighborhood, and then whether or not they did the right thing, which is to extend the "pelt" of skin past what is actually used to include more pixels all around it.
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