Ambient occlusion - how use

 

Ambient occlusion (AO) is a shading technique that darkens creases, corners, and contact points to add depth and realism; it began appearing in real‑time games around 2007 and today ranges from cheap SSAO to high‑quality ray‑traced AO — you can safely turn it off in many 4K scenarios to reclaim GPU performance with little perceived loss when other lighting tech (like DLSS and GI) is active.

Quick guide — key decisions before you toggle AO

• Performance vs fidelity: Do you need maximum frame rate at native 4K, or the last bit of visual polish?

• Type of AO: SSAO/HBAO are cheaper; ray‑traced AO is expensive but more accurate.

• Other tech in use: If you use DLSS or path tracing, AO’s visual contribution may be redundant.
  Answering those helps decide whether to keep AO on or off.

What ambient occlusion is

Ambient occlusion simulates how much ambient (indirect) light reaches a surface by darkening areas where geometry blocks light, producing soft, contact shadows that make scenes feel grounded rather than flat.

When it was invented

Real‑time screen‑space AO (SSAO) was popularized in games in 2007, credited to work at Crytek and first widely seen in Crysis; since then multiple variants (HBAO, HBAO+, GTAO, ray‑traced AO) have evolved to balance quality and performance.

How it works (high level)

Most real‑time AO operates in screen space: a pixel shader samples nearby depth/normal data and estimates occlusion from surrounding geometry. More advanced methods (HBAO/HBAO+) use smarter sampling and horizon tests to reduce artifacts and improve quality.

Why AO matters in games

AO adds subtle depth cues that improve scene readability and realism without adding explicit light sources; it’s especially noticeable in interiors, creases, and object contact points where direct lighting alone looks insufficient.

Table — When to enable AO at 4K

Criterion	Keep AO	Disable AO
GPU headroom	Low; you have spare performance	Tight; aiming for 60+ FPS at native 4K
Lighting tech	No advanced GI or ray tracing	Using path tracing or full GI
Perceptual gain	Interiors, closeups	Wide outdoor scenes
DLSS/Up‑res	Use with quality DLSS modes	Turn off to save cycles

Why players turn AO off in 4K

At 4K, shader and memory bandwidth costs scale with pixel count. AO is a screen‑space postprocess that samples many neighboring pixels; at 4K it becomes significantly more expensive, so disabling it yields a measurable FPS gain with often minor perceived loss, especially when upscaling (DLSS) or other lighting systems are active.

GPU resources AO consumes

AO primarily uses pixel shader ALU work, texture reads (depth/normal buffers), and memory bandwidth; higher‑quality AO increases sample counts and temporal filtering, raising both compute and bandwidth demands.

AO’s relevance today with DLSS and modern lighting

DLSS and other upscalers reduce the cost of high‑resolution rendering, but they don’t replace the visual role of AO. However, when games employ robust global illumination or ray tracing, AO’s marginal benefit shrinks — and DLSS can make disabling AO a practical trade‑off to hit performance targets.

Risks, trade‑offs, and recommendations

• Risk: Turning AO off can make scenes look flatter in tight spaces; test in representative scenes.

• Trade‑off: At 4K, try DLSS Quality + AO off vs native 4K + AO on to compare perceived quality and FPS.

• Actionable: Use per‑game testing; prefer HBAO+ or GTAO for best quality/perf balance if you keep AO enabled.