# Step-by-Step: Lofted Surface Along Curve in Grasshopper

1. In Rhino, use the Curve command to draw an arbitrary curve in 3D space.
2. Start Grasshopper.
3. Insert the Curve parameter.

4. Right-click on the Curve parameter and choose Set one curve. Click on the curve you drew in Rhino.
5. Right-click on the Curve parameter and choose Reparameterize. This forces Grasshopper to measure values along the curve starting with 0 and ending with 1.

6. Insert the Divide Curve component.

7. Insert a Number Slider.

8. Edit the Slider values: Under Slider accuracy, set Integer Numbers. Under Numeric domain, set 1 as the Min and 20 as the Max.

9. Connect the components: Crv output connects to the C input on the Divide Curve component; Slider output connects to the N input on the Divide Curve component. [The first connection tells the Divide Curve component what curve to divide; the second connection tells the Divide Curve component how many divisions to make.]

10. Insert the Circle CNR (Center-Normal-Radius) component.

11. Connect the components: P output on the Divide Curve component connects to the C input on the Circle CNR component; T output on the Divide Curve component connects to the N input on the Circle CNR component. [The first connection tells the Circle CNR component to draw circles centered at each of the division points; the second connection tells the Circle CNR component to “tilt” the planes on which circles are drawn to align with the Rhino curve.]

12. Insert a Loft component.

13. Connect the components: C output on the Circle CNR component connects to the C input on the Loft component. [This connection tells the Loft component to create a surface using the circles as “ribs.”]

14. Insert the Graph Mapper component and another Number Slider.

15. Right-click on the Graph Mapper component. From Graph types, choose SinC.

16. Edit the Slider values: Under Numeric domain, set 1 as the Min and 50 as the Max.

17. Insert the Multiplication component.

18. Connect the components: t output on the Divide Curve component to the input on the Graph Mapper component; output on the Graph Mapper component to the A input on the Multiplication component; output on the Slider to the B input on the Multiplication component. [These connections produce a list of numbers which is then multiplied by the output of the Number Slider. The list of numbers is determined by the y-coordinates of the graph in the Graph Mapper corresponding to the given x-coordinates (i. e., the inputs to the Graph Mapper).]

19. Connect the components: R output on the Multiplication component to the R input on the Circle CNR component. [This connection tells the Circle CNR component to draw circles at radii corresponding to the output of the Multiplication component.]

20. The Grasshopper definition is complete. Experiment by (1) selecting different curves from Rhino; (2) changing the number of divisions (first Number Slider); (3) changing the shape of the graph in the Graph Mapper component (move the grips); (4) changing the graph type in the Graph Mapper component; (5) changing the multiplication value (second Number Slider).