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The Grasshopper Primer Third Edition

1.3.4. Domains & Color

Example files that accompany this section: http://grasshopperprimer.com/appendix/A-2/1_gh-files.html

The color wheel is a model for organizing colors based on their hue. In Grasshopper, colors can be defined by their hue value in a range of 0.0 to 1.0. Domains are used to define a range of all possible values between a set of numbers between a lower limit(A) and an upper limit (B).

In the color wheel, hue corresponds to the angle. Grasshopper has taken this 0-360 domainand remapped it between zero and one.

By dividing the Hue domain (0.0 to 1.0) by the number of segments desired, we can assign a hue value to each segment to create a color wheel.

In this example, we will use Grasshopper’s domain and color components to create a color wheel with a variable amount of segments.
01. Type Ctrl+N (in Grasshopper) to start a new definition
02. Curve/Primitive/Polygon – Drag and drop a Polygon component onto the canvas
03. Params/Geometry/Point – Drag and drop a Point Parameter onto the canvas
04. Right-Click on the Point Component and select set one point
05. Set a point in the model space.
06. Connect the Point Parameter (Base Point) to the Plane (P) input of the Polygon component
07. Params/Input/Number Sliders – Drag and drop two Number Sliders onto the canvas
08. Double-click on the first Number Sliders and set the following:
    Rounding: Integers
    Lower Limit: 0
    Upper Limit: 10
    Value: 10
09. Double-click on the second Number Sliders and set the following:
    Rounding: Integers
    Lower Limit: 0
    Upper Limit: 100
    Value: 37
10. Connect the Number Slider (Radius) to the Radius (R) input of the Polygon component
When you connect a number slider to a component in will automatically change its name to the name of input that it is connecting to.
11. Connect the Number Slider (Segments) to the Segments (S) input of the Polygon component

12. Curve/Util/Explode – Drag and drop an Explode component onto the canvas. IMAGE
13. Connect the Polygon (P) output of the Polygon component to the Curve (C) input of the Explode component
14. Surface/Freeform/Extrude Point – Drag and drop the Extrude Point component onto the canvas
15. Connect the Segments (S) output of the Explode component to the Base (B) input of the Extrude Point
16. Connect the Point Parameter (Base Point) to the Extrusion Tip (P) of the Extrude Point component
17. Surface/Analysis/Deconstruct Brep – Drag and drop the Deconstruct Brep component on to the canvas
18. Connect the Extrusion (E) output of the Extrude Point component to the Deconstruct Brep (B) component

IMAGE
19. Maths/Domain/Divide Domain – Drag and drop the Divide Domain component
The Base Domain (I) is automatically set between 0.0-1.0 which is what we need for this exercise
20. Connect the Number Slider (Segments) to the Count (C) input of the Divide Domain component
21. Math/Domain/Deconstruct Domain – Drag and drop the Deconstruct Domain component IMAGE
22. Connect the Segments (S) output of the Divide Domain component to the Domain (I) input of the Deconstruct Domain component
23. Display/Colour/Colour HSL – Drag and drop the Colour HSL component IMAGE
24. Connect the Start (S) output of the Deconstruct Domain component to the Hue (H) input of the Colour HSL components
25. Display/Preview/Custom Preview – Drag and drop the Custom Preview component
26. Right click on the Geometry (G) input of the Custom Preview component and select Flatten
See 1-4 Designing with Data Trees for details about flattening
27. Connect the Faces (F) output of the Deconstruct Brep component to the Geometry (G) input of the Custom Preview component
28. Connect the Colour (C) output of the Colour HSL component to the Shade (S) input of the Custom Preview component

For different color effects, try connecting the Deconstruct Domain component to the saturation (S) or Luminance (L) inputs of the Colour HSL component.