Bloom and color grading in Unity - Deep Dive

Overview - Bloom and color grading

What is it?

Bloom and color grading are visual effects used in Unity to enhance the look of a game or scene. Bloom creates a glowing light effect around bright areas, making them appear soft and radiant. Color grading adjusts the colors and tones of the entire image to set a mood or style, like making a scene look warm, cold, or dramatic.

Why it matters

Without bloom and color grading, game visuals can look flat and less immersive. These effects help guide the player's emotions and focus by making scenes feel more alive and visually appealing. They solve the problem of dull or unrealistic lighting and color, which can reduce player engagement and enjoyment.

Where it fits

Before learning bloom and color grading, you should understand basic Unity rendering and lighting concepts. After mastering these effects, you can explore advanced post-processing techniques and shader programming to create custom visual styles.

Mental Model

Core Idea

Bloom adds a soft glow to bright spots, and color grading changes overall colors to create mood and style in a scene.

Think of it like...

Bloom is like the soft glow around a bright lamp in a dark room, and color grading is like putting a colored filter on your camera lens to change how the whole picture feels.

┌─────────────────────────────┐
│        Scene Image           │
│                             │
│  Bright Areas ──► Bloom ──► Glow Effect  │
│                             │
│  Full Image ──► Color Grading ──► Adjusted Colors │
└─────────────────────────────┘

Build-Up - 6 Steps

1

Foundation

Understanding Bloom Effect Basics

Concept: Bloom creates a glow around bright parts of an image to simulate light bleeding.

In Unity, bloom detects bright pixels and blurs them to create a soft glow. This makes lights and shiny objects look more natural and eye-catching. You can adjust intensity and threshold to control how strong the glow is and which brightness levels trigger it.

Result

Bright areas in the scene appear to glow softly, enhancing realism and focus.

Understanding bloom helps you see how light can be enhanced beyond simple brightness to affect mood and realism.

2

Foundation

Basics of Color Grading

Concept: Color grading changes the overall colors and tones of the scene to set a mood or style.

Unity’s color grading lets you adjust brightness, contrast, saturation, and color balance. You can make scenes look warmer, cooler, faded, or more vibrant. This is done by applying color curves and filters to the whole image after rendering.

Result

The entire scene’s colors shift to create a specific atmosphere or artistic style.

Knowing color grading lets you control the emotional impact of your visuals by changing how colors feel.

3

Intermediate

Configuring Bloom Parameters

🤔Before reading on: do you think increasing bloom intensity always makes the scene look better? Commit to yes or no.

Concept: Bloom has parameters like intensity, threshold, and scatter that control its look and performance.

Intensity controls how strong the glow is. Threshold sets the brightness level where bloom starts. Scatter adjusts how far the glow spreads. Balancing these avoids over-bright or washed-out images. Unity’s post-processing stack exposes these settings for easy tweaking.

Result

You can create subtle or dramatic glow effects tailored to your scene’s lighting.

Knowing bloom parameters prevents common mistakes like making scenes too bright or losing detail.

4

Intermediate

Using Color Grading Curves and LUTs

🤔Before reading on: do you think color grading only changes colors, or can it also affect brightness and contrast? Commit to your answer.

Concept: Color grading uses curves and lookup tables (LUTs) to precisely adjust colors, brightness, and contrast.

Curves let you remap input brightness or color values to new outputs, shaping the image’s tone. LUTs are preset color maps that apply complex color changes quickly. Unity supports both, allowing artists to create or import styles that dramatically change the scene’s look.

Result

Scenes can have customized color moods, from cinematic to stylized, with fine control.

Understanding curves and LUTs unlocks powerful, flexible color control beyond simple sliders.

5

Advanced

Combining Bloom and Color Grading

🤔Before reading on: do you think the order of applying bloom and color grading affects the final image? Commit to yes or no.

Concept: The order of bloom and color grading affects how the glow and colors blend in the final image.

Typically, bloom is applied before color grading in Unity’s post-processing pipeline. This means the glow effect is created first, then the colors of the whole image including the glow are adjusted. Changing this order can cause unnatural colors or glow intensity. Understanding this helps create balanced visuals.

Result

The scene looks cohesive with natural glow and color mood working together.

Knowing effect order prevents visual artifacts and ensures your artistic intent is preserved.

6

Expert

Performance and Quality Trade-offs

🤔Before reading on: do you think higher bloom quality always just costs more performance, or can it also improve visual clarity? Commit to your answer.

Concept: Bloom and color grading settings impact game performance and visual quality, requiring careful balance.

High bloom quality uses larger blur kernels and more samples, improving smoothness but costing GPU power. Color grading with complex LUTs or high precision can also slow rendering. Unity allows adjusting quality levels and using dithering to reduce banding. Profiling helps find the best settings for your target devices.

Result

You achieve visually pleasing effects without hurting game performance too much.

Understanding trade-offs lets you optimize visuals for smooth gameplay on various hardware.

Under the Hood

Bloom works by extracting bright pixels from the rendered image, blurring them using multiple passes, and then adding this blurred glow back onto the original image. Color grading applies mathematical transformations to each pixel’s color values using curves or lookup tables after the image is fully rendered. Both effects happen in the post-processing stage, meaning after the scene is drawn but before it appears on screen.

Why designed this way?

These effects are done in post-processing to avoid expensive calculations during lighting and geometry rendering. Separating bloom and color grading allows flexible control and reuse across different scenes. Early graphics hardware had limited power, so efficient blur and color mapping techniques were developed to balance quality and speed.

┌───────────────┐       ┌───────────────┐       ┌───────────────┐
│ Rendered Scene│──────▶│   Bloom Pass  │──────▶│ Color Grading │──────▶ Final Image
└───────────────┘       └───────────────┘       └───────────────┘

Myth Busters - 4 Common Misconceptions

Quick: Does increasing bloom intensity always improve image quality? Commit to yes or no.

Common Belief: More bloom intensity always makes the scene look better and more realistic.

Reality: Too much bloom causes bright areas to wash out details and look unnatural.

Why it matters: Overusing bloom can make scenes look blurry and reduce player focus on important elements.

Quick: Does color grading only change colors, or can it also affect brightness and contrast? Commit to your answer.

Common Belief: Color grading only changes the colors, not brightness or contrast.

Reality: Color grading adjusts brightness, contrast, saturation, and color balance all together.

Why it matters: Ignoring brightness and contrast changes can lead to unexpected dark or washed-out scenes.

Quick: Is the order of bloom and color grading interchangeable without effect? Commit to yes or no.

Common Belief: The order of applying bloom and color grading does not affect the final image.

Reality: Applying color grading before bloom can cause unnatural glow colors and intensity.

Why it matters: Wrong effect order breaks visual consistency and artistic intent.

Quick: Can bloom be applied to all pixels equally? Commit to yes or no.

Common Belief: Bloom affects all pixels in the image equally.

Reality: Bloom only affects pixels above a brightness threshold to simulate light glow.

Why it matters: Applying bloom to dark areas wastes performance and ruins image contrast.

Expert Zone

1

Bloom’s threshold setting is crucial for balancing glow and preserving detail; subtle tweaks can dramatically change mood.

2

Color grading LUTs can be artist-created or generated from real film scans, enabling cinematic looks that are hard to replicate manually.

3

Combining bloom with HDR rendering allows for more realistic light intensity ranges but requires careful tone mapping afterward.

When NOT to use

Avoid heavy bloom and color grading on UI elements or text, as it can reduce readability. For minimalistic or retro styles, simpler lighting without bloom or flat colors without grading may be better. Alternatives include custom shaders or simpler lighting models for performance-critical projects.

Production Patterns

In production, bloom is often used sparingly on key light sources like lamps or explosions to draw attention. Color grading is applied globally but adjusted per scene or level to maintain visual consistency. Developers use profiles and LUTs to switch moods quickly and test performance impact on target devices.

Connections

High Dynamic Range (HDR) Rendering

Bloom and color grading build on HDR by using its extended brightness range to create realistic glow and color effects.

Understanding HDR helps grasp why bloom can simulate intense light and why color grading needs tone mapping to display colors correctly.

Photography Filters

Color grading in Unity is similar to using physical filters on a camera lens to change the mood and tone of a photograph.

Knowing how photographers use filters helps understand artistic choices behind color grading settings.

Human Visual Perception

Bloom mimics how our eyes perceive bright light bleeding, and color grading adjusts colors to match emotional responses.

Learning about human vision explains why these effects make scenes feel more natural and emotionally engaging.

Common Pitfalls

#1 Applying bloom with too low threshold causing entire image to glow.

Wrong approach:

Bloom threshold = 0.0 (no cutoff, all pixels glow)

Correct approach:

Bloom threshold = 1.0 (only very bright pixels glow)

Root cause:

Misunderstanding that bloom should only affect bright areas, not the whole image.

#2 Using color grading LUT with wrong color space causing colors to look off.

Wrong approach:

Applying LUT designed for linear space in gamma space without conversion.

Correct approach:

Convert LUT to match project color space before applying.

Root cause:

Ignoring color space differences between LUT and project settings.

#3 Placing color grading before bloom in post-processing stack.

Wrong approach:

Post-processing order: Color Grading → Bloom

Correct approach:

Post-processing order: Bloom → Color Grading

Root cause:

Not understanding how effect order changes final image appearance.

Key Takeaways

Bloom adds a soft glow around bright areas to simulate light bleeding and enhance realism.

Color grading changes the overall colors and tones of a scene to create mood and style.

Both effects are applied in Unity’s post-processing pipeline after rendering the scene.

Proper tuning of bloom parameters and color grading curves is essential to avoid unnatural visuals.

Understanding the order and performance impact of these effects helps create beautiful and efficient game visuals.