RDG Color Cylinder - an Houdini Digital Asset
Abstract
This Houdini Digital Asset generates an Color Cylinder - a geometric representation of the HSV color space.
What is a Color Cylinder?
Unlike the RGB color space, whose three colors can be read as axes of a cube, the HSV color space structure is similiar to the one of a cylinder.
In this color space colors are declared by Hue, Saturation and Value. Hue describes the "color type" – like "red", "green", "blue" – on a gradient, which ranges from 0 to 360° and often is visualised as a "color wheel". The Saturation and Value (=Brighness) parts of the declaration can be interpreted as radius and height of the cylinder.
The HSV colorspace becomes handy when choosing 'similar' colors. By chaning only one or two of the components we can ensure the colors 'fit'.
Variations
The RDG Color Cylinder can be changed by adjusting its parameters.
Segments
The Segements parameter changes the number of colors displayed on the Hue gradient.
Left to right the number of segments has been increased: 3, 6 and 24 colors.
In this mapping type the 'back bone' of the cylinder displays the gradient from black to white as the center has no saturation at all — therefore center of all these color cylinders is white.
Shells
The Shells parameter adjusts the number of shells around the back bone of the cylinder. Swatches on the same radial vector sahre the same Hue with increasing Saturation.
Here the three previous cylinders with the shells.
The shell parameter was increased: 1, 3, 6
Layers
The Layer parameters defines the count of height segments in the cylinder.
The same cylinder with 2, 3 and 10 layers.
Increasing the layer count 'streches' the value that was mapped to the back bone of the cylinder.
In this case V (=Brightness).
Mapping Type
The Mapping Type changes the way Hue, Saturation and Value are mapped to Angle, Radius and Height.
Left to right the mapping type was changed:
- Angle = Hue, Radius = Saturation, Height = Value
- Angle = Hue, Radius = Brightness, Height = Saturation
- Angle = Saturation, Radius = Brightness, Height = Hue
- Angle = Brightness, Radius = Hue, Height = Saturation
Download and Installation
You can download an preview build and a sample scene of this digital asset here:
- RDG Color Cylinder (current version 2007-04-17)
- RDG Color Cylinder – sample scene
After the downloading unzip the file to a directory and install it in Houdini as Operator Type Library.
Choose File -> Install Operator Type Library... and point to the directory where the rdg_colorcylinder_[version].otl resides. Use the Install Library To option to choose where you want the type library to be available.
Conclusion
There are some features missing – like adjustable mapping interpolation.
I am not sure how to handle the dimensions (Radius and Height) in a way the bounding box of the geometry stays static while changing the layer and shell count.
2007-04-17 Georg Dümlein