Why does mobile AR show color banding?

Mobile defaults to lowp precision for fragment shaders. Color math accumulates rounding into visible bands. Mark intermediate values mediump or highp; use sRGB textures and ensure proper gamma.

How to bump precision in Unreal mobile?

Project Settings → Rendering → Mobile → Float Precision Mode = Use Half Precision. Or override per material via the Material Domain advanced settings.

Avoid 8-bit intermediates?

Render Target Format RTF_RGBA16f for HDR pipelines. RTF_RGBA8 quantizes; visible on smooth gradients.

Fix: Unreal Mobile AR Shader Precision Banding

Quick answer: Project Settings → Mobile → Float Precision = Half (or Full). Use 16f render targets. sRGB color space.

AR app tested on flagship phone: smooth. Mid-range device: visible banding on gradients. Mobile precision floor exposes the issue.

The Fix

Project Settings → Rendering → Mobile:
  Float Precision Mode:    Use Half Precision (or Full)
  Mobile HDR:              true

Material:
  Custom UVs and intermediate texture samples: mark mediump

Render Target:
  Format: RTF_RGBA16f for HDR or banding-prone gradients

Half precision is the sweet spot for most mobile GPUs — better than lowp, cheaper than full. HDR16f targets remove quantization steps.

Verifying

Re-test on mid-range device. Banding gone or much reduced. Profile: GPU time slightly up, acceptable for the visual gain.

“Half precision. HDR target. Bands smooth.”

Related Issues

For RT2D resolution, see RT resolution. For PostProcess alpha, see PP alpha.

Half precision. HDR. Smooth.