Participating Media

This section contains a list of media supported by the Ignis renderer. All number and color parameters can be connected to a shading network or texture via PExpr.

A medium is specified in the media block with a name and a type. The type has to be one of the media listed at this section below.

{
    // ...
    "media": [
        // ...
        {"name":"NAME", "type":"TYPE", /* DEPENDS ON TYPE */},
        // ...
    ]
    // ...
}

Warning

The participating media interface allows usage of PExpr but the expressions are evaluated via a surface context and do not vary inside the volume, but along the surface! This behavior is considered non-intuitive and might change in the future.

Homogeneous (homogeneous, constant)

Parameter	Type	Default	PExpr	Description
sigma_s	color	0		Scattering term.
sigma_a	color	0		Attenuation term.
g	number	0		Henyey-Greenstein phase parameter. Valid range is [-1, 1]. 0 = Isotropic, -1 = Full back scattering, 1 = Full forward scattering.

Vacuum (vacuum)

This medium has no properties and is used internally for the absence of volumes. It is better to not define a medium in the scene description instead of using this type.