I'm a little confused about what is a mipmap. From the project, it seems that the mipmap is where we can get the texture. So given any location(x,y), we can find the texture of (x,y) in mipmap? If I use level 0 of mipmap and it has (128,128), but what if my frame has resolution of (256,256)? Then how can I sample the texture?
In that case you would have to upsample the texture space. You should be able to use similar methods to downsampling like interpolation. However, I would keep in mind that upsampling would be predicting the data and would not necessarily be accurate. Here is some slides I found helpful on this concept: https://www.cs.toronto.edu/~guerzhoy/320/lec/upsampling.pdf