In addition to the below content, see also: Corona Light Material at Chaos Docs
The Corona Light Material's main purpose is illuminating the scene, but it can also be used in other scenarios. Objects with Corona Light Material applied, from the renderer’s point of view, do not differ from Corona Light objects - they are sampled the same way, and have virtually the same properties.
The typical use for the Corona Light Material is illuminating the scene with light-emitting objects which have different shapes than the ones available in the Corona Light object (e.g. light bulbs, custom-shaped lights, curved LED strips).
Creating a Corona Light Material
You can create a Corona Light Material from the menu Corona -> Light Material in the material editor.
Or by loading it in the Node material editor as follows:
(Right-click -> New Material -> Light Material)
Corona Light Material Parameters
Emission parameters
- Intensity - This option controls the intensity of the light. The intensity will be the result of multiplying the color or the texture map and the intensity value.
- Color/ Texture - A constant color can be defined here for the Corona Light Material. When a texture map is assigned, it will define the texture which is projected by the Corona Light Material.
Light Emission parameters
Emit light - When the Light Emission is Enabled, then this light is a proper emitter, casting illumination into the scene. It can be disabled to create a camera back-plate that does not alter the scene lighting.
Emit on both sides - When checked, the material will also emit light on the reverse side of the normals from the objects that are using this material. When disabled, it will only emit light using the normal front side.
Directionality - How concentrated the light emission should be around the normal. Higher values create a spotlight effect.
Occlude other lights - When enabled, the object using this light material casts shadows from other light sources. (it blocks shadow rays)
Shadowcatcher illuminator - Used in combination with the Shadow Catcher Material. If enabled, this light illuminates the shadow catcher instead of casting shadows on it. Enable for CG lights that are being added to the footage and are not present in the 2D backplate/footage.
Include/exclude parameters
Exclude/ Include: This option lets us include or exclude objects from the influence of the Corona Light Material (the excluded objects will not receive light from this Material).
Opacity parameters
Opacity - When a texture map is assigned in the opacity channel, it will define the opacity of the Corona Light Material on the mesh. This can be enabled or disabled by the checkbox next to the channel.
Advanced parameters (Visibility)
Visible directly - When enabled, make the mesh using the Corona Light Material to be directly visible to the camera at the time of rendering with color and intensity. When disabled, the mesh will be invisible.
Visible to alpha channel - When enabled, then the light will be displayed as opaque (white) in the alpha channel.
Visible in reflections - When the option is enabled, then the light reflects on the reflective objects. This can be used to disable reflections of a specific light source in other objects.
Visible in masks - When disabled, the material will not be visible in any mask from the Multipass (ID, mask, wire color,...). It will still be visible in the beauty pass and basic passes.
Visible in refractions - When this option is enabled, then the light refracts in other scene objects. This can be used to disable the refraction of a specific light source in other objects.
Generates Caustics - When enabled, the Corona Light Material will contribute to generating caustics with reflections and refractions in the scene using the fast caustics solver.
Should I use Corona Light material or Self Illumination to illuminate my scene?
This depends on the kind of lighting you want to use. Generally:
- Corona Light material technically does not differ from Corona lights, and just like them, it should be used for objects that will be the main source of strong light in your scene. That is for example lamps, cove lights, and candles - light sources that cast shadows and illuminate objects.
- Self-illumination in a Corona material (Corona Legacy Material or Corona Physical Material) should be used for objects that glow in the dark but do not really illuminate your scene. For example lava, glowing buttons, and fireflies. Light emitted by self-illumination will be clamped by MSI.
Misuse of Light material and Self-illumination may lead to excessive noise or very high render times because these two kinds of materials are sampled differently. For the Light material, Corona sends special rays to sample it like light. Self-illuminated objects are sampled like any other object.
Below is a simple guide on material usage:
| usage / light type | Corona Light Material or Corona Light object | Corona Physical material or Corona Legacy Material with Self-Illumination |
|
Using as the key light source (casting shadows, illuminating other objects) |
GOOD |
BAD - slow, noisy |
|
Subtle light source (not illuminating other objects) |
NOT RECOMMENDED | GOOD |
|
Dim light on a very big area (one big slightly glowing object or lots of slightly glowing objects) |
BAD - slow | GOOD - if the light is dim |
Notes
- The Corona Light Material is the same as the Corona Light Object from the render engine point of view (it is sampled the same way, and renders with the same performance).
- The objects with Corona Light Material are considered when setting up and using LightMix.
- Objects using the Corona Light Material cannot be instanced.
This means that if there are a lot of objects using the Corona Light Material, and especially if they are hi-poly, this will strongly affect RAM usage and the rendering performance.
The solution is to use the Corona Physical Material with the Self-illumination channel enabled instead, because it can be instanced (but please consider the limitations of self-illumination explained in this article!).
Light emission vs self-illumination - render time and RAM usage comparison:
| In this example, a Corona Light Material is used with the "Emit Light" option enabled to represent the LED lights on the Christmas tree: | In this example, a Corona Physical Material is used with the Self-illumination channel enabled to represent the LED lights on the Christmas tree: |
| Rendering time: 11:43 - RAM: 6.5 GB | Rendering time: 07:03 - RAM: 1.7 GB |
Examples
Example 1
Result A |
Result B |
In this example, the lighting comes from a Corona sky object placed in the scene. The lamps on the wall, which were imported from Chaos Cosmos are only using a translucent lampshade material with no illumination. |
A Corona Light material is applied to the lamps on the wall, but the "Emit light" option is turned off (no light contribution at all). What seems to be a bit of lighting is actually just the reflection of the lamps on the wall. |
| Passes: 60 - Noise level: 7.55% | Passes: 60 - Noise level: 8.06% |
Result C |
Result D |
In this example, a Corona Light material is applied to the lamps on the wall, and the "Emit light" option is enabled (you can clearly see the light contribution on the wall, but also on the ceiling, chairs, and other objects). The resulting image has little noise. |
Here, a Corona Physical material using the Self-Illumination channel is assigned to the wall lamps (there is subtle light contribution) and the resulting noise level is higher compared to the other examples. |
| Passes: 60 - Noise level: 6.81% | Passes: 60 - Noise level: 8.25% |
Example's conclusion
When adding additional light sources to your scene (either using lamps whose shapes are different from the ones available in the Corona Light Object or using lamps with simpler shapes), you can safely use the Corona Light material instead of using the Self-illumination channel of a Corona material (Corona Legacy material or Corona Physical material) because the Self-illumination channel will introduce additional noise to the image as it is mostly intended to be used for subtly glowing objects, not to be used as the main light source.
Example 2
Result A
In this example, the lighting comes from a Corona sky object placed in the scene and from the ceiling lamps (the lamps were taken from the Chaos Cosmos catalog and each one has a Corona Light object inside it). We are not using the Corona Light Material here at all. The Chaos Corona sign on the wall is using a translucent material without any kind of light emission.
Passes: 60 - Noise level: 9.42%
Example 2
Result B
A Corona Light material has been applied to the neon sign on the wall, but the "Emit light" option has been turned off (no light contribution at all). The reflective surfaces are being affected by the neon sign (like the floor, the stools, and the chairs), but this is only a reflection, not actual illumination.
Passes: 60 - Noise level: 9.58%
Example 2
Result C
Lastly, a Corona Light material has been applied to the neon sign on the wall, but this time, the "Emit light" option has been enabled (you can see the light contribution over the ceiling, the wall, the floor, and all over the objects in the scene, in addition to the reflections).
Passes: 60 - Noise level: 7.88%
Example's conclusion
When using custom-shaped objects that need to be emitting strong light, like the signage on the wall, the best approach is to use the Corona Light material as it will render efficiently and with little noise.
Example 3
The Corona Light Material can be applied to Corona Decals. (Corona Physical Material with self-illumination can be used like this as well!)
In this example, Graffiti textures are being used as the emission texture of a Corona Light Material which is being projected by the Corona Decals.
Corona Light Material used in combination with Corona Decal objects.
Example's conclusion
In cases where you want to represent the effect of using a blacklight, or you need a flat light-emitting object on a surface, you can use the Corona Light material (or self-illumination, depending on the specific usage) along with a Corona Decal object.