## Re: [Algorithms] Filtering

 Re: [Algorithms] Filtering From: Sylvain G. Vignaud - 2010-10-01 20:02:37 ```> On Fri, Oct 1, 2010 at 9:57 AM, Andreas Brinck > wrote: > filtered value = lerp(r0 * C0 + b0 * C1 + g0 * C2, r1 * C0 + g1 * C1 > + > b1 * C2, t) = > = (r0 * C0 + b0 * C1 + g0 * C2) * (1 - t) + (r1 * > C0 + g1 * C1 + b1 * C2) * t = > = (r0 * C0) * (1 - t) + (r1 * C0) * t + ... = > = lerp(r0, r1, t) * C0 + ... > > So in the world of non floating point numbers these two should be > equivalent right? No they're not, due to rounding. Take for example 2 texels: R=1 G=0 B=0 and R=0 G=255 B=0 Lerping in the texfetch would spawn something like: R=0 G=128 B=0 Definitely not what you're expecting! You'd want : R=0 G=255 B=something Using texfetch interpolation fails because it doesn't treat the 3 channels as one number; it won't always interpolate in the correct direction (interpreting 128 as either 0,5 or 1,5 depending on what's on the next channel) and it won't alter the other channel accordingly either. ```