The "Texture Sampling Resolution" parameter is part of RealFlow | Cinema 4D 2.5 and will be available soon.
Cinema 4D's preferences for RealFlow | Cinema 4D contain two customizable entries:
Texture Sampling Resolution
This parameter affects → "Image", → "Fill", and → "Object" emitters, as well as the → "Collider" tag's surface properties (friction, sticky, etc.). The idea is keep downscale a texture internally to keep simulation times as low as possible, because otherwise, RealFlow | Cinema 4D had to sample millions of needless pixels.
Default Cache Folder
Here you enter the standard path where simulation cache files will be stored. The actual folder is then specified in under → Scene > Cache > Cache Folder (macOS | Windows).
Reset Default
Return to the standard entires of the RealFlow | Cinema 4D preferences.