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Greg Hughes avatar image
Greg Hughes asked ·

Convert a colour HDRI in Skydome to B&W?

Is there a way to convert a colour HDRI added to the Skydome light to B&W (parameter or connect a node to colour correct)?

hdri skydome
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Mads Drøschler avatar image
Mads Drøschler answered ·

Pipe the HDRI into an Arnold Color Correct node and set saturation to 0.
Then link the Color Correct node to the Skydome.

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Greg Hughes avatar image
Greg Hughes answered ·

Thanks for the tip. I am new to Houdini so it took a while for me to figure out how to set it up. This seems to be the way:

(1) In Skydome set Light tab-Color Type: Shader and click on Open floating operator icon (cross with arrow) on right of Color Shader parameter and select the Arnold_vopnet item under arnold_skydome_light1-shopnet.
(2) Click on Jump to operator icon next to it (arrow icon) to navigate to arnold_vopnet node. Double click on the node and connect an Image node to the OUT_light (rgba to color). Select the HDRI for Texture tab-Filename.
(3) Connect a Color Correct node in between these nodes (rgba to input; rgba to color). In color_correct1 node set Saturation: 0

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rachid Hadj Abderrahmane avatar image
rachid Hadj Abderrahmane answered ·

You do not need Color Correct node for that, Just activate check mark: Single Channel in image Node.

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Stephen Blair avatar image
Stephen Blair answered ·

Color Correct with Is Luminance enabled

rgba to float with Mode = Luminance


both convert to greyscale using a formula like those shown here: https://en.wikipedia.org/wiki/Grayscale

But Arnold will do the conversion using the right coefficients for the working color space

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