ImagePlanes

Actual pixel data.

total number of planes is NumTilesX * NumTilesY * NumChannels; The total image size can be up to 32k x 32k. For an RGBA pass, that is 16GB of data. So in the future we might want to keep a pool of tiles around and share them to avoid allocating/freeing so much memory. The layout of tiles is by subsample. So all tiles are the "width/height" of the full image, but describe different subsamples. So a 4k by 4k with TileSizeX=4 and TileSizeY=3 would have a pixel layout like this.

TileIndex:

| 0 1 2 3 | 0 1 2 3 | 0 1 2 3 | | 4 5 6 7 | 4 5 6 7 | 4 5 6 7 | | 8 9 10 11 | 8 9 10 11 | 8 9 10 11 |

| 0 1 2 3 | 0 1 2 3 | 0 1 2 3 | | 4 5 6 7 | 4 5 6 7 | 4 5 6 7 | | 8 9 10 11 | 8 9 10 11 | 8 9 10 11 |