high vs low quality SMAA

I'm using SMAA as the main anti-aliasing technique for my scenes, I understand that using the highest quality is better in term of graphics but worse in terms of performance.

However, I really want to understand what does "high" quality mean in this case? what does it change in the SMAA algorithm to make it produce high-quality anti-aliasing?

sorry if this sounds a dumb question

 

from: https://github.com/Unity-Technologi...haders/SubpixelMorphologicalAntialiasing.hlsl:

* SMAA_PRESET_LOW (%60 of the quality)
* SMAA_PRESET_MEDIUM (%80 of the quality)
* SMAA_PRESET_HIGH (%95 of the quality)
* SMAA_PRESET_ULTRA (%99 of the quality)

and

#if defined(SMAA_PRESET_LOW)
#define SMAA_THRESHOLD 0.15
#define SMAA_MAX_SEARCH_STEPS 4
#define SMAA_DISABLE_DIAG_DETECTION
#define SMAA_DISABLE_CORNER_DETECTION
#elif defined(SMAA_PRESET_MEDIUM)
#define SMAA_THRESHOLD 0.1
#define SMAA_MAX_SEARCH_STEPS 8
#define SMAA_DISABLE_DIAG_DETECTION
#define SMAA_DISABLE_CORNER_DETECTION
#elif defined(SMAA_PRESET_HIGH)
#define SMAA_THRESHOLD 0.1
#define SMAA_MAX_SEARCH_STEPS 16
#define SMAA_MAX_SEARCH_STEPS_DIAG 8
#define SMAA_CORNER_ROUNDING 25
#elif defined(SMAA_PRESET_ULTRA)
#define SMAA_THRESHOLD 0.05
#define SMAA_MAX_SEARCH_STEPS 32
#define SMAA_MAX_SEARCH_STEPS_DIAG 16
#define SMAA_CORNER_ROUNDING 25
#endif

So basically the higher the preset, more search steps and smaller threshold. High and Ultra additionally do corner rounding.

I don't think HDRP exposes ultra out of the box but you could easily expose it with small modification if needed.

 

Thanks!!!!!