Bloom is the technical name for a glowing effect in imagery. It creates a feathered light glowing around an object. Bloom can be accomplished in Blender. The process for adding Bloom and Glare in Blender differs in Eevee and Cycles.
How to Add Bloom in Eevee
Blender’s realtime render engine is called Eevee and it’s capable of adding a glow or bloom effect very easily. The effect will be based off the strength of emissive materials in the scene.
How to add bloom in 25 seconds
To activate bloom (glow) in Eevee, go to the Render Properties panel. Scroll to the tab labeled “Bloom” and check the box.
A glow effect will now be visible around emissive materials in renders and render previews.
The effect will be stronger on materials with a higher emission strength.
Bloom Settings (Eevee)
When bloom is activated in the render properties, several settings appear.
The threshold is what strength of emissive material will be affected by the bloom. If it is set to 1, only materials with an emission strength above 1 will have the glow effect.
The knee setting adjusts the transition between the areas that are below and above the threshold.
The radius is how far the bloom effect spreads. Higher values spread farther.
A color can be added to the bloom effect. The default color is white and this will generally be what is used. In this example image, a red color has been added to the bloom.
Having a color other than the emission may be an effect you want…or not.
The intensity setting is how powerful the glowing bloom effect will appear in Eevee. A higher intensity will be more noticeable.
The intensity slider has a range of zero to one, but higher values can be entered manually.
Clamp places a limit on how strong any single bloom pixel can be. If we have a scene where certain materials are very bright, we can limit the intensity effect with a clamp.
Here’s a link to the Blender manual’s documentation on the Eevee Bloom effect.
How to Add Glow / Bloom in Cycles
Glare Node explained in 26 seconds
Although we can’t create a bloom effect in Cycles the same way we can in Eevee, we are able to use the compositor and the glare node to get a similar effect.
Using the compositor to achieve a glow effect in Cycles can be set up before or after we render a single image.
For animations, the compositor nodes should be set up before rendering so they affect all frames of the animation.
Adding a Glare Node in the Compositor
To add glare to a render in Cycles, we go to the compositor. We can find the compositor by changing to the compositing workspace.
In order to use nodes, we have to ensure the “Use Nodes” box is checked in the compositor.
With “Use Nodes” checked, we should see a node setup that looks like this:
To add glow to a rendered image in the compositor, press “Shift + A” to add a node. Search for a glare node (found in the filter category).
Place the Glare Node between the render layers node and the composite output node.
The best way to view the effects of the glare node in the compositor is to open another editor screen, change it to an Image Editor and select “Render Result” from the image selector at the top.
Adding Multiple Glare Types
We can add multiple glare types by adding multiple glare nodes. Place a second glare node between the first glare node and the composite output node. Use one glare node for each type of glare we want to add.
Glare Node Settings
The Glare Node in Blender’s compositor has several settings to adjust how the glare appears in the render. We will cover those settings here.
The first setting is glare type and it defaults to “Streaks.” Other options include Ghosts, Fog Glow and Simple Star. Here are examples of each, exaggerated for demonstration.
While Fog Glow may be the simplest and closest to the bloom effect used in Eevee, you can see other types give us some interesting effects. Of course the intensity of these filters can be adjusted.
The glare type chosen will determine which other options are available. Here are the settings displayed for each glare type.
Glare Quality is the box which defaults to “Medium” in the above images. This is the resolution of the glare and available options are: High, Medium and Low. Higher quality means a more defined effect with higher resolution.
Iterations is an option for all glare types except fog glow. This is how many times the glare filter will be applied. The value can be as high as five. The more iterations, the more intricate the effect will be.
The glare effect is mixed with the original image by the glare node. The “Mix” setting adjusts how much of the original image is visible compared to the filter effect.
The mix setting range is from -1 (full original image) to 1 (full glare effect). Zero will be a 50/50 mix of the image. Here are some comparisons of glow mixes for reference:
As with the bloom effect in Eevee, the glare node can have a minimum threshold. Pixels with emission strength below the threshold will not have the glow effect applied to them.
Other Glare Settings
As you see there are a handful of other settings on the glare node. They are mostly self-explanatory. If you experiment with them, you may see small differences in the glare effect on your render.
Here is the Blender documentation on the glare compositing node.
Although the methods of adding a glow effect are different in Eevee and Cycles, it can be done in both. I have a lot of other helpful content on this site, so please have a look around.
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