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Black Body Emission
The emission uses Temperature (in Kelvin) and Power to control the color and intensity of the light, respectively.
The following settings are listed for the Black Body Emission settings, but many of the settings are shared with the Texture emission settings. The main difference is whether the colour comes from the Black Body temperature or from the texture settings of the diffuse material (see figures below).
- Texture - Sets the light source's efficiency. You can set this to a value or texture. Keep in mind that real-world lights aren't 100% efficient at delivering power at their specified wattage - a 100-watt light bulb doesn't deliver 100 watts of light. This parameter enters the real-world values.
- Power - The light source's wattage. You should set each light to their real-world wattage - for example, set a desk lamp to 25 watts, a ceiling lamp to 100 watts, and an LED light to 0.25 watts.
- Surface Brightness - Causes emitters to keep a constant Surface Brightness, independent of the emitter surface area.
- Keep Instance Power - Enabling this option with Surface Brightness disabled and Uniform Scaling applied to the object causes Power to remain constant.
- Double Sided - Allows emitters to emit light from the front and back sides.
- Temperature - The temperature (in Kelvin) of the Black Body emission's light.
(Black Body emission only, not applicable for Texture Emission)
- Normalize - Ensures all normal vectors have the same length for the Black Body emission - this keeps the emitted light's luminance constant if the temperature varies. this is enabled by default.
(Black Body emission only, not applicable for Texture Emission)
- Distribution - Controls the light pattern. You can set this to a Greyscale or RGB image so that you can load an Image texture or file. the Image texture's Projection nodes adjust the light's orientation and direction.
- Sampling Rate - Choose what light sources receive more samples.
- Light Pass ID - The Light Pass ID captures the respective emitter's contribution.
- Visible On - Enables light source visibility on diffuse surfaces. It allows you to enable or disable the ability for Black Body emission's or Texture emission's light sources to cast illumination or shadows on diffuse objects. Disabling this option disables emission - it's invisible in diffuse reflections, but is still visible on specular reflections. It's also excluded from the Direct light calculation. This option is enabled by default.
- Visible On - Enables the light source's visibility on specular surfaces, and allows you to hide emitters on specular reflections/refractions. This is enabled by default.
- Transparent Emission - Allows light sources to cast illumination on diffuse objects, even if the light source is on transparent material.
- Cast Shadows - Enables light sources to cast light and shadows on diffuse surfaces, letting you disable direct light shadows for Mesh emitters. To make this option work, the Direct light calculation must include the emitter (the sampling rate must be greater than 0). This option is enabled by default.
- Efficiency or Texture – This setting is used to set the efficiency of the light source. 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.
Below you see an example of two different PNG used for the Black Body Emission Texture.
Below you see an example of a color and an image used for the Body Emission Texture on a Diffuse Red object.
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