When using Arnold it is best to use a tiled mip-mapped texture format such as .exr or .tx that has been created using maketx.
.tx textures are:
- Tiled (usually the tiles are 64×64 pixels).
- Mip-mapped.
Due to (1), Arnold’s texture system can load one tile at a time, as needed, rather than having to wastefully load the entire texture map in memory. This can result in faster texture load times, as texels that will never be seen in the rendered image will not even be loaded. In addition to the speed improvement, only the most recently used tiles are kept in memory, in a texture cache of default size 512 mb (can be tuned via options.texture_max_memory_MB). Tiles that have not been used in a long time are simply discarded from memory, to make space for new tiles. Arnold will never use more than 512 mb, even if you use hundreds, or thousands of 4k and 8k images. But then, if you only use a handful of 1k textures, this will not matter.
Due to (2), the textures are anti-aliased, even at low AA sample settings. Neither of these are possible with JPEG or other untiled/unmipped formats (unless you tell Arnold to auto-tile and auto-mip the textures for you, but this is very inefficient because it has to be done per rendered frame, rather than a one-time pre-process with maketx).
As this is a frequently asked question we have provided both the question and answer in this thread.
Lee Griggs
Arnold rendering specialist
AUTODESK
