Soft cone emitter

../../../_images/softcone.jpg

Soft cone emitter

Emitter This emitter has a uniform angular distribution over a cone defined by its angular radius, and falls off to zero up to a larger cone

It is defined by:

  • A base light emission spectrum, setting dependence of radiance to wavelength

  • A filter shader modulating the radiance across the geometry surface

  • A scalar shader defining the tangent of the inner “full” cone angular radius

  • A scalar shader defining the tangent of the outer “falloff” cone angular radius. If the falloff cone angle is smaller than the full cone angle, no falloff occurs.

Luminous values may be normalized using the metric and quantity parameters as follows:

  • Custom metric : the emission properties are normalized to match the quantity defined by value and quantity

  • Base spectrum : base child defines the light quantity, as a spectral flux per instance or a spectral emittance per unit area, depending on the quantity parameter. multipler is unitless

It should be noted that all normalization occurs before the posmod function is applied.

Note

This emitter was previously made using a Generic Emitter associated to a Soft Cone Distribution before Ocean 2017 R5

Understanding metric

The actual physical emission values are derived from metric and quantity parameters

Metric

Quantity

Value

Unit

Base spectrum

Spectral flux (per instance)

base * multiplier

W/m

Base spectrum

Spectral emittance

base * multiplier

W/m3

Custom

Luminous flux (per instance)

value

lumen

Custom

Luminous emittance

value

lumen/m2

Custom

Energy flux (per instance)

value

W

Custom

Energy emittance

value

W/m2

For instance, in Base Spectrum Spectral Emittance mode, the base spectrum child values are multiplied by multiplier, and this sets the source emittance, in watts per wavelength unit (meters) per unit area (m²).

In Custom Luminous Flux mode, the value sets the lumen value per instance.

Children nodes

Spectrum base

The base emission spectrum

Filter shader posmod

The spectral position modulation function

Scalar shader tanfull

The tangent of the full cone angular radius

Scalar shader tfalloff

The tangent of the falloff cone angular radius

Parameters

name

type

description

metric

list

Sets the metric mode (Custom or Base spectrum)

quantity

list

Sets the quantity or unit of the metric

value/multiplier

real

Defines the value (Custom metric) or the multiplier (Base spectrum metric)

Ocean XML 6.1 example

<emitter type="softcone" name="emitter" metric="custom" quantity="lumflux" value="50">
     <spectrum type="blackbody" name="base" temp="3000" gain="1e-06"/>
     <filtershader type="constant" name="posmod" value="1"/>
     <scalarshader type="uniform" name="tanfull" value="0.5"/>
     <scalarshader type="uniform" name="tanfalloff" value="2"/>
</emitter>