The Octane Light tag is created by adding a light in OctaneRender®, which will then add a "Light Tag" to the new light at the same time. All of the settings related to the light, outside of the Cinema 4D-supplied attributes for the light, reside in the Octane Light Tag. The Light Tag consists of five tabs: Basic, Main, Light Settings, Visibility and Motion Blur. The Basic tab is the classic Cinema 4D tab, where you can name the light and choose the layer for the light to reside; the other tabs are explained in the following sections.


General Settings of the Light Tag

These settings apply to all light types supported by OctaneRender®. The image below illustrates the components of the Octane Light tag, as seen in the Attribute Manager.


octane light tag


Main Tab

The Main tab contains settings to choose the Light type, enable the light and to choose the type of emission of the light source.

Normal and IES Light Icons

Select the icon that represents the light type desired. When you press the IES icon, you can start using special light data with the "ies" file extension. This topic is discussed in detail in "IES Lights".

Spot Button

Define or remove.

Enable

Enable/Disable the use of the light.

Type

Choose between Blackbody and Texture emission for the light.


Light Settings Tab

The Light Settings tab contains most of the settings needed to control the characteristics of the light.

Power

The Power attribute value represents light energy in Watts. To get a realistic render output, enter real world light wattage values into the power setting, representing the proper values for the desired light source. For example, standard bulb wattage typically has a range of between 25 to100 watts and radiates a brightness of about 250-1600 Lumens. In this same range of lumens, Halogen bulbs are 18-72 watts for the same brightness as standard bulb. LED bulbs fall into the 4-20-watt range for standard bulb brightness. Of course, any value can be used, but if realistic results are desired, it is best to stick with known wattage values.

POWER




Temperature

Set the emission color of the light in degrees Kelvin, commonly used for light description. The following chart shows the visible spectrum of light mapped to the Kelvin scale:


Attribution: Ilumi.co


This scale suffices in the case of typical lights commercially available for home or business use, however, there are plenty of other situations where lights are actually colored in with different methods (such as cinematic gels that are used to color lights on movie shoots.) The Kelvin scale refers to color temperature (from warm to cool) and cannot represent specific colors in the RGBSpectrum or Gaussian spectrum. This can be easily done via the Texture option, discussed in the following section, or by enabling Use Light Color, and choosing the color from the Cinema 4D color picker.

Texture

This option uses Octane nodes for more direct control to color the light source, with either RGB Spectrum, Gaussian, or Image Texture nodes, beyond basic color temperature control as offered by Kelvin scale in the Temperature slot. HDR images can be used, but may add noise, requiring an increase in Sampling Rate. For details see Texture Emission. 

NOTE

Procedural Generator nodes work differently when used in the Texture slot of lights. Instead of seeing the pattern projected into the scene, the pattern instead is visible on the light shource itself; therefore, any scene illuminated with a Procedural Generator in the Texture slot of an Octane Light will have generator pattern averaged over the light area, and, likely, not very useful to you. Instead, use Procedural Generators in the Distribution slot of an Octane Light if you wish to see that pattern projected into the scene (as shown in the following examples).


Distribution

This option is used to define the pattern of the light cast, and is useful for creating "gobo Lights" and "IES Lights", for example. You can create various light patterns using any image or Procedural Generator. In the example below, various light patterns are created using grayscale images in the Distribution channel (alpha images work as well). Once you have defined the  image in the Distribution channel, you can position, scale and rotate the texture by adding a Transform node (using the Octane Image Texture), explained in the "UsingTextures" section. For IES lights, just connect the ".ies" file into Distribution pin via an Image Texture node. 


IMPORTANT

The Texture Projection option in the Image Texture or Procedural Generator must be set to Perspective (when you position/rotate/scale the light, the texture will move with the light as well). 



distribution




Surface Brightness

This option increases or decreases the brightness value of the light according to the size of the Emitter Object. Enable to see that brightness changes when the Emitter object is scaled. Disable to allow brightness to remain constant, regardless of the scale of your Emitter Object.

surface brightness




Keep Instance Power

Enabling this option with Surface Brightness disabled and Uniform Scaling applied to the object causes Power to remain constant, as shown in the images below. The size of the light has been changed, but the illumination output is the same, regardless of the light size, with Keep Instance Power enabled. Note that the shadows and caustics will conform to the size of the light, as expected.

keep instance POWER




Double Sided

This option is used to emit both sides of the Emitter Object. Default is Disabled.

double-sided




Normalize

Normalize will keep the Luminance value constant as the temperature values of the emission change. When it is disabled, the Luminance value will change as the temperature changes. According to this, in the low temperature parts of the Visible Spectrum (orange, red), the light brightness will decrease, and at the higher points (white, blue) the light brightness will increase. Default is Enabled.

normalize


Sampling Rate

The sampling rate determines how many samples will be used in the shading of the light being cast. In some cases, there may be more than one light in your scene, and some of them may create noise in a certain area. In such cases you can reduce noise by defining more samples for a given light. However, you may need to set the sample rate of other lights when doing this, because this option works as a "ratio". You can think of blackbody emissions on the scene as "sample weighting". In the example below, which has not been denoised, "Light A" has 100x more samples than "Light B," which is far noisier. In most cases, the default value of 1 works well-enough, and you shouldn't need to change it unless something specific occurs in your renders.


sampling rate


Visible on Diffuse

This option enables the light source to be visible on diffuse surfaces (defaults to ON), enabling or disabling light sources from casting illumination or shadows on diffuse objects. Disabling this option will disable emission, i.e., it won’t be visible in diffuse reflections, but still be fully visible in specular reflections. It will also be excluded from the direct light calculation.

visible on diffuse





Visible on Specular

This option will enable the light source to be visible on specular surfaces (defaults to ON). This allows users to hide emitters on specular reflections/refractions only.

visible on specular




Cast Shadows

This option enables shadows to be cast from the light source, and provides the means to disable direct light shadows for mesh emitters (defaults to ON).

cast shadows




Transparent Emission

This option determines whether or not the emission power should be scaled with opacity (defaults to ON). This is useful if you want to control the light in your scene without your emitters being directly visible. But there are cases when transparent emitters should not emit light. Consider the following example: if you define any alpha image on the Opacity channel of this object, the reflection will not be correct. However, if you turn off "Transparent Emission", the reflection will look correct. 



transparent emission


regular plane object with emission assigned to

become a light object


(you can look at the blackbody emission section on 

how to do this)

alpha image texture assigned to diffuse 

material's opacity channel


Reflection is wrong when transparent 

emission is "on"


reflection is correct when transparent 

emission is "off"


Use Light Color

This option will use the color of the light from the "General" tab in the light options of Cinema 4D.

use light color





Opacity

This option is to define the opacity value in Blackbody Emission. 

Light Pass ID

This option will set the Light ID for the specific light (lights with the same ID will be contained in the same light pass/AOV). The light pass ID is used for light linking and excluding, as discussed here.

light pass id




Visibility Settings Tab

The Visibility Settings tab determines whether or not the light will be visible to the camera (but still cast light), visible to shadows, or completely invisible.

Camera Visibility

With this option you can control whether the light will be seen by the camera. When "on", the light object is rendered. When "off", the object itself is not rendered, but illumination other features remain the same.

camera visibility





Shadow Visibility

This option works for normal polygon objects rather than light objects. For a detailed description, please refer to the Octane Object Tag section.

General Visibility

This option is basically a global combination of the Camera visibility and Shadow visibility options, and honors the Transparent Emission setting. Unlike the Camera and Shadow visibility options, General Visibility offers a slider, to gradually decrease these effects.


Motion Blur Tab

The Motion Blur tab enables/disables motion blur for the light.