Table of Contents

 

This article explains the settings and values for the Corona Volume Material in Cinema 4D.

 

Overview


 

Corona Renderer is a physically-based renderer, and just like in the real world, volumetric effects are a property of the material that light passes through, and not a property of the light source itself. This means that volumetrics are created in Corona for Cinema 4D using materials, and no special settings are required in the light sources themselves.

 

 

Volume


Absorption

Color – The absorption is controlled by setting the color that an originally white ray has after traveling the specified distance in the medium.

Texture – This slot defines the texture map or shader that is used for the absorption.

Mix mode – This parameter controls the blending mode of the texture map or shader over the absorption color.

Mix strength – This value controls the intensity of the texture map or shader that is being used.

Distance – Lowering this value makes the effect stronger. Distance 0 is a special value that disables the effect completely.

If the Mix strength is set to 100%, the texture map or shader completely overrides the color unless the Mix mode is set to a different blending mode than Normal.

 

 

 

Scattering

Color – The strength and color tint of the volumetric scattering inside the material. Setting a non-black value enables volumetric scattering/SSS effects from this material. Each time light scatters inside the material, it gets multiplied by this value.

Texture – This slot defines the texture map or shader that is used for the scattering.

Mix mode – This parameter controls the blending mode of the texture map or shader over the scattering color.

Mix strength – This value controls the intensity of the texture map or shader that is used.

Directionality – Directionality equal to 0 produces isotropic (diffuse) scattering, positive values produce forward scattering, and negative values produce backward scattering. A default value of 0 is suitable for most media, with the exception of clouds where a higher positive number produces the effect of a silver lining. Values close to 1 or -1 increase the amount of image noise.

Single bounce only – When enabled, only a single bounce (direct lighting) is scattered in the medium. This results in a biased (darker) but faster rendering. Useful e.g. for rendering god rays.

If the Mix strength is set to 100%, the texture map or shader completely overrides the color, unless the Mix mode is set to a different blending mode than Normal.

 

Emission

Color – This is the emission from the volume (glowing plasma effect). Controlled by setting the color that is emitted from each distance of ray traveling in the medium.

Texture – This slot defines the texture map or shader used for the emission.

Mix mode – This parameter controls the blending mode of the texture map or shader over the emission color.

Mix strength – This value controls the intensity of the texture map or shader that is used.

Distance – Lowering this value makes the effect stronger. Distance 0 is a special value that disables the effect completely.

If the Mix strength is set to 100%, the texture map or shader completely overrides the color unless the Mix mode is set to a different blending mode than Normal.

 

Volume mapping

Mode – This parameter allows for using different modes to map the volume.

On surface – When using this mode, the textures are resolved at the volume boundary (resulting in a medium that is still homogeneous inside even though it is mapped on the surface).
Inside volume – When using this mode, the textures are evaluated inside the volume along the ray (resulting in a true heterogeneous medium).

Step size – When the mapping mode is set to Inside Volume, textures are sampled along the ray once per step. This parameter defines the length of the step and thus also the number of steps along the ray. Increasing the step size leads to faster rendering, but a noisier result. Decreasing the step size leads to slower rendering with higher-quality results.

 

 

Advanced


 

Visibility

 Propagate masks – Specifies the propagation of non-shading render elements (masks) after interaction with the material. Available modes are:

Never – Mask passes are never propagated through the material, i.e. the material is always visible in masks.
Through reflection – Mask passes are propagated through the material if reflection occurs.
Through refraction – Mask passes are propagated through the material if refraction occurs.
Always – Mask passes are always propagated through the material, i.e. the material is never visible in masks.
Invisible in masks – This mode makes the material invisible in masks.

Advanced options

Material ID – Defines an ID for the material that can be used in the Corona Compositing tag or in the Corona Data shader.

Alpha mode – Specifies how the objects with the material are visible in the alpha channel. Available modes are:

Default – This is the default mode. In this mode, the material alpha value is derived from its opacity and refract components.
Always black – In this mode, the material alpha value is black (material shows as transparent).
Always white – In this mode, the material alpha value is white (material shows as opaque).

 

 

 

Examples


Absorption Distance: 10 m
Absorption Distance: 20 m
Absorption Distance: 50 m
Absorption Distance: 75 m
Scattering Directionality - 0.99
Scattering Directionality - 0.75
Scattering Directionality - 0.5
Scattering Directionality - 0.25
Scattering directionality 0
Scattering directionality 0.25
Scattering directionality 0.5
Scattering Directionality 0.75
Scattering Directionality 0.99