Exercise: Creating one sample "T" cross section

Create one inverted "T" cross section for the tunnel roof along the path. To complete the roof, construct one cross section first and later replicate it along the path. For the section you need a plane that is perpendicular to the path and one that is parallel to the horizontal component of the path.

Use plane2 to create a line that defines the height of the roof.

In the Node Types dialog select the Line node. The node line1 appears in the Graph view.
Select the ByStartPointDirectionLength technique for line1. There are three required inputs: StartPoint, Direction and Length.
Draw a wire from the StartPoint input on line1 to the overall node on plane1.
Draw a wire from the Direction input on line1 to the overall node on planeplane2. The plane is basically a vector normal to the plane at its origin and therefore can be used as a direction.
Enter a fixed number in the Length expression field. It should fit the scale of your model. In this case a value of 3 is appropriate.
(Optional) In the Length expression field, enter the expression 5-plane1.Z. This makes the length responsive to the path. The 5 ensures that the top of the roof is at least 5 units above ground plane.
Note: To create the ribs or outrigger of the roof you need to first define the direction the cross members should point. You can derive this direction from intersecting the two planes you already have, since their intersection will create a Direction that is always horizontal and always perpendicular to the curve.
In the Node Types dialog select the Direction node. The node direction1 appears in the Graph view.
Select the AtPlanePlaneIntersection technique for line1. There are two required inputs: plane0 and plane1.
Draw wires from the plane0 and plane1 inputs on the direction1 node to the overall nodes of plane1 and plane2 respectively.
Record User Changes into Transaction file.
Note: Now that you have the direction of the ribs, you can create two lines that point in opposite directions from the planes.
In the Node Types dialog, select the Line node with the ByStartPointDirectionLength technique. The required inputs are StartPoint, Direction and Length.
1. Draw a wire from the StartPoint input to the plane1 overall node.
2. Draw a wire from the Direction input to the direction1 overall node.
For Length, you will use a fraction of the length of the vertical line. Create that relationship interactively: select the vertical line line1 then enter a period to access valid parameters, and double click on Length. Multiply the result by 0.5.
1. Click Length to open its expression field.
2. In the Graph, select the plane1 node. plane1 appears. in the expression field.
3. Enter a period character (.). A drop down appears listing valid parameters.
4. Enter L. The drop down parameter list scrolls to the Length parameter.
5. Double click on Length. The parameter Length appears in the expression field after the period.
6. Enter *0.5 after Length.
The final expression for the Length input should look like this:
line1.Length*0.5
line2 is created. It is perpendicular to and half as long as line1.
Right click on the line2 node you just created, and select Copy.
In the Graph, right click away from any nodes, and select Paste Node(s). A new node line3 is added to the model. It is an exact copy of line2.
On line03, click the Length input, and change the multiplication factor at the end of the expression from *0.5 to *-0.5. line1.Length*-0.5 This inverts the direction of line3.
Record User Changes into Transaction file.

You should see an upside down T now, which is the roof section.