The Black Body Emission node allows a material to emit light. Emission nodes are used with the Diffuse material type and can be used to make any surface with these attributes cast light. Figure 1 shows the Black Body Emission button in the Create Render Node window of Maya’s Hypershade window.
The Blackbody Emission type uses Temperature (in Kelvin) and Power to control the color and intensity of the light.
Figure 1: The Blackbody Emission button in the Create Render Node window of the Hypershade.
Black Body Emission Parameters
Figure 2 shows the parameters of the Blackbody Emission node.
Figure 2: The Blackbody Emission parameters in the Attribute Editor.
Temperature (in Kelvin) of the light emitted by the blackbody emission. Lower values result in warmer colors, higher values result in cooler colors.
Is the wattage of the light source. Each light in the scene should be set to its real world wattage. This power will be multiplied by the texture input, where 1.0 means 100% of the power (so by default 0.025 means 2.5% gives 2.5W of light).
A Boolean value providing the option to ensure all the normal vectors have the same length for the Blackbody emission in order to keep the luminance of the emitted light from a Blackbody constant if the temperature varies.
Controls the pattern of the light. An image texture or IES profile can be used as an emission pattern. Figure 3 shows the result of a Turbulence texture connected to the Emission pattern of a Blackbody Emission texture that has been applied to a sphere casting light on a plane below it. The texture appears in the light pattern cast on the plane. If Emission pattern is set to zero the texture will not cast light into the scene.
Figure 3: A Turbulence texture is connected to the Emission Pattern of a Blackbody emission texture casting light on the plane.
Texture or efficiency
Is used to determine how far the light is cast into the scene based on its power settings. No light is 100% efficient at delivering the power at the specified wattage (a 100 watt light bulb does not actually deliver 100 watts of light.) The efficiency setting can be used to enter the real world values. These values can be used to create very realistic light settings. For example, a standard 100 watt incandescent bulb would only be approximately 2.0% efficient whereas a 25 watt compact fluorescent light will be 10% efficient. These will both produce around the same quantity of light in real life. This setting can also be connected to a texture to alter the color of the emitted light.
Allows users to choose which light sources will receive more samples. Adjusting the light source sampling rates in the scene will lead to a better balance between light sources. The sampling rate can also be set to 0 (zero), which means the emitter will be excluded from the direct light calculation.
Is useful when the brightness of the emitter is independent of the area of the surface. Enabling this option will cause emitters to keep the surface brightness constant independent of the emitter surface area.
Enables the Blackbody emission sources from casting illumination or shadows on diffuse objects. Disabling this option will disable emission.This means the surface will not be visible in diffuse reflections, but still be fully visible in specular reflections. It will also be excluded from the direct light calculation.
Light Pass ID
Is used in conjunction with the Light Pass ID Render Element. Setting this value allows for rendering the contribution of the light in a separate render pass provided the Light Id pass of the same ID value is enabled in the Render Pass section of the OctaneRender settings.