Are there ideal dimensions (width and height) for texture files?

Yes.  Use large 16K or 32K textures, whenever possible. Using multiple smaller textures (e.g. 4K or 8K) results in more files, which will take longer to load and may not produce the best quality textures.

Texture width and height dimensions should always be a power of two.

• Here are several examples of correct power of two texture width and height dimensions:
  • 1024 x 1024 (1K)
  • 2048 x 2048 (2K)
  • 4096 x 4096 (4K)
  • 8192 x 8192 (8K)
  • 16384 x 16384 (16K)
  • 32768 x 32768 (32K)
  • 16384 x 4096 (Different width and height is fine, as long as they are both a power of two)

Automatic texture upscaling

Any texture image that does not use power of two for width or height will automatically be upscaled to the nearest power of two. For example, if you upload a 17000 x 17000 texture, it will be automatically upscaled to 32768 x 32768. This automatic upscaling does produce more texture data for our servers to store and load, which can effect how much you may pay for the asset. For this reason, it is still best to configure your application to produce and export power of two textures.  Most applications already do this.

For reference, this the size of each texture as measured by Nira (calculated as Gigapixels):

1024 x 1024 (1K) = 0.00211 GP
2048 x 2048 (2K) = 0.008 GP
4096 x 4096 (4K) = 0.03 GP
8192 x 8192 (8K) = 0.06 GP
16384 x 16384 (16K) = 0.25 GP
32768 x 32768 (32K) = 1 GP

Nira supports an unlimited amount of textures and you can mix any size textures together in the same asset.  So, for example, you can have 50 x 32K textures (50 GP) + 250 x 16K (63 GP) textures in one asset (total 113 GP).