Why does my game look blurry at 4K?

Blur at high resolution is almost always FXAA or TAA over-smoothing. FXAA blurs edges indiscriminately; TAA blurs in motion because its history buffer rejects pixels that move faster than its search radius. Toggle AA off to confirm, then switch to a sharper method like SMAA or reduce TAA blend strength.

What causes trails and ghosts behind moving objects?

TAA ghosting happens when motion vectors are wrong or missing. Particles, alpha-masked foliage, and skinned meshes often omit motion vectors, so the history buffer retains stale color samples and smears them into a trail. Enable motion vectors for every animated surface.

Does DLSS or FSR hallucinate content?

Yes. Both upscalers trained on general content can invent pixel patterns that were never in the frame, especially for thin geometry, UI text, and particle effects. Always render UI at native resolution after upscaling, and test at multiple DLSS and FSR quality levels on reference scenes.

How to Debug Anti-Aliasing Artifacts in Games

Quick answer: Every anti-aliasing method has a fingerprint. FXAA produces uniform blur, TAA produces motion ghosting, MSAA produces dotted edges on alpha-masked surfaces, and DLSS or FSR can invent pixel patterns that were never in the frame. The debugging workflow is: toggle off, toggle each method on in turn, and capture identical frames for layered comparison.

Anti-aliasing bugs are among the most frustrating reports a game team gets, because the artifact looks different on every capture and the player has no vocabulary for what they are seeing. “It looks weird in motion” and “edges are shimmery” can mean ten different things. Once you learn the characteristic artifact of each AA method, you can match player screenshots to specific code paths and know exactly where to start debugging.

Know the Fingerprint of Each Method

Each AA method makes a different compromise. Understand the trade-off and you understand the artifact.

FXAA is a post-process that scans the final frame for edges and blurs them. It is cheap, it softens everything, and it cannot tell an edge from a high-contrast texture detail. The signature artifact is blurry text, blurry specular highlights, and a general feeling of softness at high resolution. FXAA at 4K looks worse than no AA at 4K because the natural pixel density is already fine enough.

TAA (Temporal Anti-Aliasing) accumulates samples from previous frames using motion vectors to reproject pixels. The signature artifacts are ghosting behind moving objects, smearing around particles, and a subtle softness during camera motion. TAA quality depends entirely on correct motion vectors: any surface that moves without reporting a motion vector will ghost.

MSAA (Multi-Sample Anti-Aliasing) samples geometry edges multiple times per pixel. It handles polygon silhouettes beautifully but does not touch alpha-tested surfaces like foliage, chain-link fences, or billboards. The signature artifact is clean character outlines against flickering or aliased vegetation. MSAA also conflicts with deferred rendering.

SMAA is a morphological AA that searches for specific edge patterns. It is sharper than FXAA and cheaper than TAA, but it can miss thin geometry entirely. The signature artifact is jaggy power lines and antenna-thin geometry that other methods would have caught.

DLSS/FSR/XeSS upscalers render at a lower resolution and reconstruct to display resolution using temporal samples plus a model (learned for DLSS, analytical for FSR 1, temporal for FSR 2+). The signature artifacts are hallucinated texture detail, pixel dancing on thin geometry, and UI text that looks wrong if it was rendered before upscaling. DLSS is sharper than FSR 2 but can invent patterns. FSR 2 is less aggressive but softer.

Step One: Toggle Off First

Always start debugging by disabling AA entirely. If the artifact persists, it is not an AA bug — it is a lighting, shader, or texture issue that AA was accidentally hiding. Many “AA bugs” turn out to be bad normal maps or Z-fighting that only became visible when AA stopped smoothing them.

// Expose AA mode in a console command so QA can toggle at runtime
enum AAMode { Off, FXAA, SMAA, MSAA2x, MSAA4x, TAA, DLSS, FSR };

void SetAAMode(AAMode mode) {
    renderer->currentAA = mode;
    renderer->RebuildPostProcessChain();
    Log::Info("AA mode set to ", AAModeName(mode));
}

Ask the player (or your QA tester) to reproduce the issue with AA off and capture a screenshot. If the artifact is invisible without AA, you have confirmed it is AA-related and can proceed to isolate which method.

Step Two: Cycle Through Each Method

Once you have confirmed an AA issue, cycle through each available method on the same scene at the same camera position. Capture a screenshot for each mode. Load all captures into an image editor as layers and flip between them. Differences will jump out: a specific area blurry in FXAA but sharp in SMAA, a trail behind a moving character in TAA but not MSAA, a hallucinated pattern in DLSS that nothing else produced.

For in-motion artifacts, capture video with each method. Record at 60 FPS, play back frame by frame, and watch the moving parts. TAA ghosting becomes obvious when you step through frames — you will see smeared color trailing the moving object by 2 to 5 frames.

Step Three: Check Motion Vectors

If the artifact is TAA-specific ghosting, the root cause is usually wrong or missing motion vectors. Particles, skinned meshes, foliage, and water are the common offenders. Visualize the motion vector buffer directly:

// HLSL debug visualizer for motion vectors
float4 DebugMotionVectors(float2 uv) {
    float2 mv = SampleMotionVectorBuffer(uv);
    float mag = length(mv) * 100.0;
    float angle = atan2(mv.y, mv.x);
    return float4(hsv2rgb(float3(angle, 1.0, saturate(mag))), 1.0);
}

Any moving surface that renders black in this visualization has no motion vector and will ghost under TAA. Usually the fix is to output motion vectors from the material’s vertex shader by comparing current and previous world positions.

Step Four: Account for UI and Post-Processing Order

DLSS and FSR output upscaled frames, and anything composited after upscaling must also be rendered at the output resolution. If your UI is baked into the low-resolution render target before upscaling, DLSS will try to upscale it and produce the worst possible version of your HUD. Always render UI as a separate pass after upscaling. Bloom, tone mapping, and chromatic aberration should also run at output resolution to avoid doubled or misregistered effects.

Step Five: Test on Reference Scenes

Keep a set of reference scenes that stress each AA method: a scene with thin geometry for SMAA, a scene with alpha-tested foliage for MSAA, a scene with fast-moving particles for TAA, and a scene with dense UI for upscalers. Run all methods against all scenes before every release. An AA regression usually shows up as a delta on exactly one scene-and-method pair.

“Players kept reporting a ‘smear’ on our bullet tracers. We tried everything — particle settings, trail lengths, blend modes — until we realized our tracer billboards did not write motion vectors. TAA was blending five frames of tracer color into a smear. One line in the material fixed it.”

Related Issues

For rendering regressions in general, see how to test game performance regression in CI. If your AA tests produce visual bug reports, learn automated screenshot capture for game bug reports.

Build a reference scene set with four cameras and six AA modes. Capture the matrix before every release. You will catch AA regressions the day they happen, not three weeks after ship.