Back to Blog
Neutral lut6/30/2023 ![]() If that occurs, try forcing the use fixed-point LUTs by turning off the Floating Point 3D LUTs item on the Rendering tab of the preferences. Sometimes even though the driver reports that the LUTs can be floating point, you will see banding in the final images. If RV detects that the card probably can’t do a good job with the floating point hardware it will switch to a fixed-point representation using 16 bit integer LUTs. Not all cards are equally capable with 3D LUTs and floating point. RV has two different algorithms for applying the LUTs on the GPU: using floating point or fixed-point integer textures. Alternately, you use a lightbox and assuming you have a well calibrated neutral monitor, “eyeball” the LUT by comparing the film to the monitor. For film look simulation, it’s often necessary to have special hardware to measure and compare film recorder output. There are a number of ways to create a LUT. When interpolating between sample values, RV uses linear interpolation for channel LUTs and tri-linear interpolation for 3D LUTs. This is usually more of an issue with 3D LUTs than channel LUTs since they have fewer samples per dimension. When applied in hardware, the LUTs are interpolated when a value is not exactly represented in the LUT. ![]() If RV can determine whether the floating point LUTs are usable itself it will default to whatever is appropriate. ![]() the 3D LUTs) so if you notice banding or noisy output when using floating point LUT storage, you may have better luck with the 16 bit integral representation. Not all hardware is capable of processing LUTs stored as floating point (esp. Internally, RV will store the LUT as either half precision floating point or 16 bit integral. ![]() This makes it possible for any of the LUTs to transform colors outside of the typical range on both input and output. The values the LUT produces can be outside of the range. Both types of LUT are preceded by an input matrix which can scale high dynamic range data into the range of the LUT input (which is the range ). In the case of a 3D LUT there can also be an additional channel pre-LUT which can be used to shape the data. The first three are per-source while there is only a single display LUT for each RV session.Įach of the LUTs can be either a channel LUT or a 3D LUT (the difference is explained below. RV provides four points in its color pipeline where LUTs can be applied: just after reading the file and before caching directly after the cache (file LUT), just before display transforms (look LUT), and as one of the display transforms (display LUT). Look up tables (LUTs) are useful for approximating complicated color transforms, especially those which have no known precise mathematical representation. ![]()
0 Comments
Read More
Leave a Reply. |