Legacy Documentation: Version 4.5
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Bloom

Blooming is the optical effect where light from a bright source (such as a glint) appears to leak into surrounding objects. The Bloom image effect adds bloom and also automatically generates lens flares in a highly efficient way. Bloom is a very distinctive effect that can make a big difference to a scene and may suggest a magical or dreamlike environment especially when used in conjunction with HDR rendering. On the other hand, given proper settings it’s also possible to enhance photorealism using this effect. Glow around very bright objects is a common phenomena observed in film and photography, where luminance values differ vastly. Bloom is an enhanced version of the simpler but optimized FastBloom and older BloomAndFlares image effects.

This example shows a proper HDR glow as created by the <span class="doc-keyword">Bloom</span> effect. In this scene, bloom uses a threshhold of 1.0 indicating that only HDR reflections, highlights or emissive surfaces glow, but common lighting is generally unaffected. In this particular example, only the car window (sporting the reflection of HDR sun values) glows.
This example shows a proper HDR glow as created by the Bloom effect. In this scene, bloom uses a threshhold of 1.0 indicating that only HDR reflections, highlights or emissive surfaces glow, but common lighting is generally unaffected. In this particular example, only the car window (sporting the reflection of HDR sun values) glows.
Here is the same scene shown without the <span class="doc-keyword">Bloom</span> effect. Using Bloom can add realism to your scenes.
Here is the same scene shown without the Bloom effect. Using Bloom can add realism to your scenes.
Example showing <span class="doc-prop">Anamorphic Lens Flares</span> result as created by the <span class="doc-keyword">Bloom</span> effect
Example showing Anamorphic Lens Flares result as created by the Bloom effect

As with the other image effects, this effect is only available in Unity Pro and you must have the Pro Standard Assets installed before it becomes available.

Properties

Property: Function:
Quality High quality preserves high frequencies and reduces aliasing.
Mode Choose complex mode to show advanced options.
Blend The method used to add bloom to the color buffer. The softer Screen mode is better for preserving bright image details but doesn’t work with HDR.
HDR Whether bloom is using HDR buffers. This will result in a different look as pixel intensities may leave the [0,1] range, see details in tonemapping and HDR.
Cast lens flares Enable or disable automatic screen based lens flare generation.
Intensity The global light intensity of the added light (affects bloom and lens flares).
Threshhold Regions of the image brighter than this threshold receive blooming (and potentially lens flares).
RGB Threshhold Chose different threshholds for R, G and B.
Blur iterations The number of times gaussian blur is applied. More iterations improve smoothness but take extra time to process and hide small frequencies.
Sample distance The max radius of the blur. Does not affect performance.
Use alpha mask The degree to which the alpha channel acts as a mask for the bloom effect.
Lens Flares The type of lens flare. The options are Ghosting, Anamorphic or a mix of the two.
Local intensity Local intensity used only for lens flares. 0 disables lens flares entirely.
Local threshold The accumulative light intensity threshold that defines which image parts are candidates for lens flares.
Stretch width The width for anamorphic lens flares.
Rotation The orientation for anamorphic lens flares.
Blur iterations The number of times blurring is applied to anamorphic lens flares. More iterations improve smoothness but take more processing time.
Saturation (De-)saturates lens flares. If 0, lens flares will fully receive the Tint Color.
Tint Color Color modulation for the anamorphic flare type.
1st–4th Color Color modulation for all lens flares when Ghosting or Combined is chosen.
Lens flare mask Mask used to prevent lens flare artifacts at screen edges.

Blend Modes: Add and Screen

Blend modes determine the way that two images will be combined when overlaid. Each pixel from the base image is combined mathematically with the pixel in the corresponding position in the overlay image. Two blend modes are available for this image effect, Add and Screen.

Add Mode

When the images are blended in Add mode, the values of the color channels (red, green and blue) are simply added together and clamped to the maximum value of 1. The overall effect is that areas of each image that aren’t especially bright can easily blend to maximum brightness in the result. The final image tends to lose color and detail and so Add mode is useful when a dazzling “white out” effect is required.

Screen Mode

Screen mode is so named because it simulates the effect of projecting the two source images onto a white screen simultaneously. Each color channel is combined separately but identically to the others. Firstly, the channel values of the two source pixels are inverted (ie, subtracted from 1). Then, the two inverted values are multiplied together and the result is inverted. The result is brighter than either of the two source pixels but it will be at maximum brightness only if one of the source colors was also. The overall effect is that more color variation and detail from the source images is preserved, leading to a gentler effect than Add mode.

Hardware Support

This effect requires a graphics card that supports Shader Model 2. See the Graphics Hardware Capabilities and Emulation page for further details and a list of compliant hardware.

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FastBloom
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