Bloom
Make bright highlights glow by extracting them, blurring them, and compositing the result back onto the base frame.
Post-processing is nested under Rendering pipeline , so the broader pipeline usually still applies here.
Interactive playground
Tweak the operator or scene live so the article connects to an immediate visual result.
Bloom
Extract the brightest parts of the frame, blur them, and fold the glow back into the main image.
Base frame
Reference viewBloom composite
Interactive compareRaise the threshold for tighter highlights, or increase intensity to make the glow dominate more of the frame.
Family
Rendering pipeline -> Post-processing
Full-frame effects such as bloom and temporal anti-aliasing layered after base rendering.
Builds on
3 topics
Read these first if you want the surrounding pipeline context.
Unlocks
1 next topic
Use these follow-ups when you want to keep turning the image-processing pipeline forward.
Learning paths
2
This topic appears in curated graphics progressions so the next step is obvious.
Choose this over that
Glow, dynamic range, or temporal cleanup?
Bloom, tone mapping, and TAA all change the final frame, but their jobs are very different.
Bloom
Choose this when: Bright highlights should visibly bleed into neighboring pixels for a glow effect.
Choose something else when: The issue is fitting HDR values into range or stabilizing shimmer across frames.
Tone Mapping
Choose this when: High dynamic range values still need to be compressed into a displayable interval.
Choose something else when: The base image is already in range and now only needs post glow.
Temporal Anti-Aliasing (TAA)
Choose this when: Temporal flicker and subpixel instability are the problem, not missing glow.
Choose something else when: The image is stable but lacks highlight bloom.
Problem
Bright highlights often look unnaturally hard-edged in a raw render. Real optical systems and many stylized pipelines spread some of that energy into neighboring pixels.
Intuition
Bloom isolates bright regions, blurs them, then adds or composites the blurred result back over the image. The blur converts a tiny intense highlight into a larger soft halo.
Core idea
- Threshold or otherwise extract the bright parts of the frame.
- Blur that bright-pass image, often at one or several scales.
- Composite the blurred glow back onto the base frame with a chosen intensity.
Worked example
A small emissive sign may be only a handful of pixels wide in the base render. After bloom, it emits a soft surrounding halo that makes it feel brighter and more cinematic.
Complexity
Bloom is usually several full-screen passes: extraction, blur, and composition. The cost depends on blur radius, resolution, and how many levels or scales you use.
When to choose it
- Choose it when bright highlights should feel like they spill light into nearby pixels.
- Tone mapping should already have handled the main HDR compression before bloom is tuned artistically.
- Choose TAA later when the main issue is flicker and instability, not missing glow.
Key takeaways
- Bloom is post-processing based on bright-pass extraction and blur.
- It is closely tied to tone and dynamic-range decisions.
- It produces a halo effect rather than changing object visibility or geometry.
- Its final step is a compositing operation back onto the original frame.
Practice ideas
- Implement a bright-pass plus separable blur bloom pipeline.
- Compare bloom with different thresholds and intensities on the same frame.
- Inspect the difference between blooming before and after tone-mapping choices are finalized.
Relation to other topics
- Gaussian blur is the smoothing engine inside bloom.
- Tone mapping shapes the base image that bloom is layered onto.
- Alpha compositing or additive blending returns the blurred glow to the final frame.
Build on these first
These topics supply the mental model or preceding stage that this page assumes.
Gaussian Blur
Smooth an image with a weighted local average so noise shrinks before thresholding, edge detection, or later analysis.
Alpha Compositing
Combine foreground and background layers with transparency so multiple images or passes can share the same final frame.
Tone Mapping
Compress HDR-style scene values into a range a normal display can actually show while keeping highlights under control.
What this enables
Once the current operator feels natural, these are the most useful follow-up jumps.
Related directions
These topics live nearby conceptually, even if they are not strict prerequisites.
Screen-Space Ambient Occlusion (SSAO)
Approximate local ambient shadowing from the depth and normal buffers so creases and contact areas feel less flat.
Shadow Mapping
Use a depth map from the light’s point of view to decide whether a visible surface point is blocked from that light.
Temporal Anti-Aliasing (TAA)
Accumulate information across frames so shimmering and unstable subpixel detail become calmer over time.
More from Post-processing
Stay in the same family when you want parallel operators built from the same mental model.
Paths that include this topic
Follow one of these sequences if you want a guided next step instead of open-ended browsing.
Color and tone pipeline
Track how values move from color spaces and gamma into dynamic-range compression, equalization, dithering, and compositing.
Raster pipeline
Follow the classic rendering path from clipping and rasterization into visibility, shadows, occlusion, and temporal cleanup.
From the blog
Pair the graphics atlas with recent writing from the broader site whenever you want a wider engineering lens.