Translucency & SSS
Translucency simulates light passing through thin geometry — the orange glow of a hand against the sun, the rim of a leaf, the wax around a candle flame. Genesis ships a fast wrap-lighting approximation with a thickness map, view distortion, and an art-directable color.
Light transmitting through a back-lit leaf as the light orbits behind it.
When to use it
- Skin — ears, fingers, and nostrils under a strong back-light.
- Foliage — leaves transmitting sunlight.
- Wax, candles, and jade — a surface glow from internal scatter.
- Magic FX — a sustained inner glow on cloaks, slimes, and ghosts.
Rim is a view-aligned fresnel that brightens silhouettes regardless of light direction. Translucency depends on the light direction — back-lit surfaces glow, front-lit ones do not. Both can stack.
How it works
The shader computes a wrap-lit term pow(saturate(dot(-L + N * _SSSDistortion, V)), _SSSPower), multiplies by _SSSColor and the sampled thickness, and adds the result to the lit output. Distortion controls how much the normal bends the light direction; higher values produce a more diffuse, wrap-around glow.
A leaf with and without translucency. Drag to compare.
Properties
Usage
- Enable Translucency and assign a thickness map; bake one with the AO Baker or paint it manually.
- Pick a Transmission Color (warm flesh, green sap, amber wax).
- Tune Distortion until the wrap matches reference — 0.2–0.4 for skin, 0.5–0.7 for leaves.
- For magical surfaces, raise Ambient SSS so the glow persists without a back-light.
material.SetColor("_SSSColor", new Color(0.95f, 0.45f, 0.32f)); // skin
material.SetFloat("_SSSDistortion", 0.25f);
material.SetTexture("_SSSThicknessMap", skinThickness);Tips & gotchas
- Thickness is inverted relative to occlusion — bright means thin. Bake with that in mind, or invert the AO Baker output.
- This is a wrap-lit approximation, not a real diffusion profile, so multi-bounce shadows will not be accurate.
- Pairs with Normal Mapping: small-scale normal detail helps the SSS term break up evenly across the surface.
- Cost is roughly three ALU per pixel, cheap enough to ship.
Related
- Rim Lighting — view-aligned glow versus light-driven SSS.
- Iridescence — color shift over a translucent base.
- Normal Mapping — drives micro-detail in the SSS wrap.
- AO Baker — bake the thickness map.