How to use Bloom and Glare?




In Corona Renderer, all post-processing options, including Bloom and Glare, can be adjusted in real time during and after rendering. This applies to both regular and interactive rendering.



Bloom and Glare can be controlled in the "Post" tab of the Corona VFB:





Bloom


Bloom creates a large, soft glow around bright areas in the image, ideal for adding softness to windows as an example, or giving a soft glow around a candle flame. Hue Power and Shift let you adjust the hue of the effect rather than have it purely depend on the color of the light source.



Bloom and Glare disabled - note the sharp, bright pixels on the surface of the water and plants. These are the reflections of  strong sunlight:




Bloom enabled (glare size is set to 0) - note that the bright pixels are now surrounded by soft halos, making them appear more natural:





Glare


Glare creates a sharper, more-focused glow with rays from bright areas in the image. This is ideal for creating a “starburst” effect around bright highlights on cars, from bright light sources, on gemstones, etc. The Hue Power and Shift parameters affect Glare in the same way as Bloom.


Glare enabled (bloom size is set to 0) - note that the bright pixels are now turned into star-shaped flares: 




Bloom and Glare


When both bloom and glare are enabled, the two above effects are combined, resulting in both soft glow and sharp streaks:

 

 



Render Elements


Bloom and Glare Render Element


Bloom and Glare can be saved into a dedicated render element - CShading_BloomGlare:



This CShading_BloomGlare render element can be applied on top of an image without Bloom and Glare using the Add operation or can be used to mask some Bloom and Glare areas, change their colors, etc. 



Other Render Elements


CShading_Beauty and CShading_LightMix render elements can be created and saved with or without Bloom and Glare effects applied. It is also possible to toggle bloom only or glare only using the checkboxes in the CShading_Beauty, CShading_LightMix, and CShading_BloomGlare render element settings:





Bloom and Glare and DOF


While the Bloom and Glare effect features some photographic settings (such as aperture) and is dependent on lens properties in real life, in Corona Renderer, it is currently completely separated from other camera and lens effects such as depth of field and motion blur. Bloom and glare will simply affect all pixels in the image which are bright enough, and changing photographic parameters such as aperture shape or blade count will not affect them in any way (e.g. using depth of field with blade count set to 5 will not automatically produce glare with 5 streaks).


Depth of field enabled with Blade count set to 6 in the Corona Camera's properties. This produces hexagon-shaped bokeh as expected. Bloom and Blare effect is disabled: 


The same image with Bloom and Glare enabled. In this case, Sides is set to 6, which produces glare with 6 streaks, which is expected: 


The same image again, with Bloom and Glare enabled, and Sides set to 4. This produces glare with 4 streaks, which is not expected since in real life the number of glare streaks is dependent on the number of aperture blades:




Bloom and Glare and Realism


Bloom and glare are effects that happen in real life due to the imperfections of camera lenses and sensors, so they often appear in real-life photos. Remember that enabling them will usually increase the realism of your renders. On the other hand, the effect should not be exaggerated, and Bloom and Glare should remain subtle.


Image with Bloom and Glare disabled:


The same image with Bloom and Glare enabled:


Note how the scene realism is boosted, not only by adding the strong glare around the sun, but also thanks to the subtle glow around the ceiling lamps. 




Fixing jagged edges


Bloom and Glare, in addition to increasing scene realism, can be used to improve the appearance of "jagged edges" (edges with hard pixels visible in high contrast areas). For more information, see: I can see jagged edges in my rendering!




Examples


Size


Default size (30):


Reduced size (10):


Increased size (60):



Bloom intensity:


Default bloom intensity (1):


Reduced bloom intensity (0.5):


Increased bloom intensity (5):



Glare intensity


Default glare intensity (1):


Reduced glare intensity (0.5):


Increased glare intensity (5):



Bloom and Glare Threshold


The Bloom and Glare effect is applied to the brightest pixels in the rendered image. The Threshold setting controls the minimum brightness which is considered for the Bloom and Glare effect. Increasing the threshold will apply Bloom and Glare only to the brighter pixels. Reducing it will allow the Bloom and Glare effect to be applied to pixels that are less bright. 


Default threshold value (1):


Reduced threshold (0.01):


Increased threshold (10):



Color intensity


Color intensity controls how saturated the Bloom and Glare effect is. Higher values mean higher saturation. 


Default color intensity (0.3):


Reduced color intensity (0):



Increased color intensity (1):



Color shift


Color shift changes the hue of the coloring added to the Bloom and Glare effect. 


Default color intensity and color shift:


Color intensity 1, color shift 0.25:


Color intensity 1, color shift 0.5:


Color intensity 1, color shift 0.75:



Streak count


Streak count defines the number of streaks for the glare effect. 


Streak count 3 (default value) produces 3 "lines" in the glare effect, which results in 6 streaks in total:


Streak count reduced to 2 (minimum value):


Streak count increased to 4:


Streak count increased to 8 results in a more "sun-like" appearance of the glare effect:



Rotation


Rotation of the glare effect in degrees.


Rotation set to 15 (default value): 


Rotation reduced to 0 results in a more symmetrical glare effect:


Rotation increased to 90:



Streak blur


Streak blur decides whether the glare streaks should be sharper or more blurry.


Streak blur set to 0.2 (default value):


Streak blur reduced to 0:


Streak blur increased to 0.5:


Streak blur increased to 1 (maximum value):



Custom aperture and the Aperture Editor


Starting with Corona Renderer 6, it is now possible to enable advanced Bloom and Glare effects through the Aperture Editor. Simply enable the "Custom aperture" checkbox and then click on the "Editor..." button. This will launch an editor which can be used to fine-tune advanced Bloom and Glare options:


Since there is a large number of settings in the Aperture Editor, usually some trial and error is required to get the desired effects. Below are examples of using various options:


"Sides" checkbox disabled - this results in the aperture being circle-shaped, rather than polygonal, and thus removes the streaks making the glare effect uniform and similar to the bloom effect:


Occlusion set to 0.2 - occlusion makes the aperture shape stretched vertically or horizontally, thus reducing some of the glare effect streaks:


Occlusion set to 0.92 - increasing the occlusion to high values will result in the glare effect being stretched in one direction:


Peripheral grating (default values) - enabling the peripheral grating option adds a halo effect to Bloom and Glare:


Peripheral grating length set to 1 - increasing the length value makes the colorful rainbow effect stronger: 


Lens scratching - enabling this effect modifies the existing glare shape by either adding more streaks or stretching the effect in one direction:


Lens dust - this effect simulates dust particles on the lens surface:



Below are four examples of various Aperture Editor settings which help to produce different "looks" of the same image: