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Pseudo Transparency (Composite Blending) Shader

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Rion edited this page Jun 4, 2026 · 5 revisions

SGENPT-MIX - Pseudo Transparency (Composite Blending) Shader

SGENPT-MIX is a RetroArch shader designed to recreate the "composite transparency" look many retro systems relied on (most famously the Sega Genesis / Mega Drive dither patterns used for pseudo transparency). This is especially useful when you run RGB/component output where dithering is normally visible as vertical lines or checkerboards instead of blending like it did over composite on a CRT.

It also works great for other 8 to 16-bit content that uses dithering tricks, and it can be useful for PS1 content as well.

What it fixes

A classic example is the Sonic 1 waterfall, which looks like hard dithering on clean RGB output, but blends like transparency on composite/CRT. With SGENPT-MIX you can simulate that blending on RGB output.

Where to find it

In a Batocera installation, both presets are located directly in the dithering folder:

  • /dithering/sgenpt-mix.slangp
  • /dithering/sgenpt-mix-multipass.slangp

How to enable it in RetroArch (quick way)

  1. Start a game
  2. Open the RetroArch Quick Menu [HOTKEY] + South button or Shift+F1
  1. Go to Shaders
  2. Set Video Shaders = ON
  3. Load the shader / preset:
    • Load shader: .../dithering/shaders/sgenpt-mix.slang
    • Or load a preset that uses SGENPT-MIX
  4. Save:
    • Save Game Preset (only for that game)

Tip: If you are using other CRT/composite shaders already, you can often append SGENPT-MIX before/after them depending on the look you want.

Recommended usage

Option A: Use it by itself (fast)

  • Great for quickly blending dithering patterns into pseudo transparency without adding extra processing.

Option B: Combine with a shader

  • SGENPT-MIX can be combined with:
    • RetroArch's own "composite" options in some cores
    • Other composite/NTSC shaders if you want more signal artifacts

In many cases, SGENPT-MIX shader gives a very convincing result without making the image overly noisy.

For CRT RGB users

If you run RGB/Component to a consumer CRT or PVM/BVM and want "composite style blending" for dithering-based transparency:

  • SGENPT-MIX is the cleanest way to simulate composite blending while still keeping your RGB signal path.

RGB (no blending)
Dithering is visible (no composite-style blend).
RGB + SGENPT-MIX
Dither patterns blend into pseudo transparency.

RGB (no blending)
Dithering is visible (no composite-style blend).
RGB + SGENPT-MIX
Dither patterns blend into pseudo transparency.

GIF comparisons (LCD capture)

These two GIFs down below show the difference SGENPT-MIX makes when simulating Pseudo Transparency (Composite Blending) on an RGB output.

Important: These captures are not from a CRT — they are recorded from an LCD on purpose, just to demonstrate the effect more clearly.
On a CRT the end result will naturally look different due to scanlines, phosphor glow, and analog blending.


Shinobi III: Return Of The Ninja Master
Sonic The Hedgehog 2

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