Overview
Fast Approximate Anti-Aliasing detects high-contrast edges in the final image and blends samples along the edge direction.
ExtendedSource checked
FXAA
Smooths jagged image edges with a fast post-process filter.
Quick Facts
Compact metadata for implementation and discovery.
- Category
- Rendering
- Difficulty
- Beginner
- Family
- Post-Process Anti-Aliasing
- Tier
- Extended
- Status
- Verified
- Review
- Source Checked
- Sources
- 1
- Formulas
- 1
- Relationships
- 4
- Code example
- Ready
- Visualization
- Ready
Core Concepts
luminance contrastedge directionpost-process filterscreen-space blend
Quick facts
Complexity
Runtime and memory behavior at a glance.
Best
O(pixels)
Average
O(pixels)
Worst
O(pixels)
Space
O(1) extra
When to Use
- Use when a cheap post-process anti-aliasing pass is needed.
- Use when low-cost real-time anti-aliasing is a central requirement.
When Not to Use
- Avoid when preserving very fine texture sharpness is more important than smoothing edges.
- Avoid when the renderer cannot provide the buffers, samples, or lighting data the technique needs.
What It Does
- Detects contrast edges
- Estimates edge direction
- Blends nearby pixels
Use Cases
- Low-cost real-time anti-aliasing
- Post-processing pipelines
- Fallback edge smoothing
Inputs
- Rendered color image
Outputs
- Filtered color image
Key Formulas (1)
Luminance contrast
contrast = maxneighbor luma − minneighbor luma
contrast = max_neighbor_luma - min_neighbor_lumaDetects whether a pixel sits near a strong edge.
Pseudocode
- 1.Read the current pixel and neighbors
- 2.Measure local luminance contrast
- 3.Skip low-contrast pixels
- 4.Estimate the edge direction
- 5.Blend samples along that edge
Canonical Example
- Input
- edge pixels = black next to white
- Output
- output = intermediate blended edge
- Explanation
- FXAA detects the contrast and smooths the transition.
Implementation Notes
- Tune contrast thresholds on representative scenes, not only test patterns.
- Debug with simple geometry, known lights, and visualized intermediate buffers.
- Keep a tiny example with expected output beside the implementation.
Common Pitfalls
- Running FXAA before tone mapping or at the wrong color space can change its behavior.
- Coordinate-space mismatches often cause artifacts that look like math errors.
- Not defining boundary, empty, or degenerate inputs before implementation.
Interactive Mechanism Walkthrough
Spatial Primitive & Sweep-Line CanvasShow a jagged high-contrast edge being softened by neighboring pixel samples.
Step 1 of 5: Read the current pixel and neighbors
rendering-pipelineNotes
FXAA is fast but may blur fine texture detail.
Sources (1)
What each reference supports for this entry.
NVIDIA FXAA Whitepaper
DocumentationNVIDIA whitepaper describing Fast Approximate Anti-Aliasing.
Open sourceExplore Next
Good next jumps from the relationship graph, ranked for useful discovery.
Relationships
View full relationship pageAlternative toMSAA
FXAA smooths edges after rendering instead of storing multiple coverage samples.
Alternative toTemporal Anti-Aliasing
FXAA is a single-frame post-process alternative to temporal accumulation.
Related Algorithms
Tags
GraphicsAnti-AliasingFilteringScreen-Space