In computer graphics, texture filtering or texture smoothing is the method used to smooth textures used in 3D models. Some consoles use texture filtering.
In emulation, texture filtering can be applied even if the original console did not use it. Many emulators support such features.
|Console||Texture Filtering||Types of filtering|
|Sega Dreamcast||✓||Bilinear, trilinear, anisotropic|
|PlayStation 2||✓||Bilinear, trilinear, Anisotropic|
|GameCube||✓||Bilinear, trilinear, anisotropic|
|Xbox||✓||Bilinear, trilinear, anisotropic|
|PlayStation Portable||✓||Bilinear, trilinear|
|Wii||✓||Bilinear, trilinear, anisotropic|
Types of Texture Filtering
|Filtering type||What it does||Pros||Cons|
|Nearest neighbor||This method sorts pixels into the nearest place relevant to it's placement in the original resolution, in order to display the image at whatever resolution you specify.||
|Bilinear||This linear filtering method uses color data from the pixels in a nearest-neighbor texture, and combines multiple bits of color data in order to replace some of the pixels with an averaged-out version of the colors, so that the colors gradually switch rather than jump to a new color.||
|Trilinear||This linear filtering method does the same thing as bilinear filtering, except it passes through twice, giving a smoother gradient.||
|HQx||A texture scaling algorithm. Scales up a nearest-neighbor version of the texture and fills in the gaps with copies of the pixels next to said gaps.||
|2xSaI||A texture scaling algorithm. Scales the texture and fills edges in with a mixture of pixels taken from the source and randomly-guessed colors.||
|xBR||A modified version of HQx. It detects edges better, which works better for curved lines, or for slopes that are greater than/less than 45 degrees.||
|xBRZ||A modified version of xBR, which is very similar except it's better at scaling up smaller features consisting of <10 pixels.||
Durante's Hybrid and Deposterization Filters for PPSSPP
PPSSPP has a scaling option known as "Hybrid." There's also an option called "Deposterize." Posterization, meaning a sharp contrast in hue from one pixel to another (very common in low-quality gifs) has been a problem plaguing texture scaling algorithms for quite some time. Durante's filter switches between xBR and bilinear/bicubic filtering depending on the texture information. On top of this, the "Deposterize" option tackles posterization edges in compressed textures, allowing for a smooth gradient rather than a sharp transition. Although it's not perfect (a perfect scaler sadly isn't possible with today's computing power) it's still great and it's recommended to use for PPSSPP if you have the specs.
Forum post from the creator of xBR, explaining how the algorithm works (Warning: is slightly hard to read due to the amount of jargon and big words)