ACOUSTIC ANALYSIS - Designing Raked Audience Seating

Creating Construction Lines

In this tutorial you will work through the process of creating a simple raked audienceseating area.

1. Open  Raked Seating.eco  from the Tutorial Files directory located in your main ECOTECT Install directory.
   
   There are three zones in this model; Auditorium, Construction Lines, and the default Outside zone.
   
   
2. Firstly we need to create a vertical construction line (about 5000mm high) at the front of the stage in the middle.
   
   To do this, make sure the Construction Lines zone is current. Then using the Line tool, snap to the Mid-point of the base of the stage at the front.
   
   Left click to insert the first node, then with the Control key pressed down (constrains the cursor to the Z axis only) drag the mouse upwards until a height of around 5000 is reached.
   
   Left click again to accept the second node, then hit the Escape key to finish the line.
   
   
3. Now that we have the first vertical construction line we can array them in the X direction, with a gap of around 1000mm, to mark the distance between the rows of seating.
   
   The easiest way to do this is to use the Object Transformation panel.
   
   

   		Make sure the vertical line is selected, then enter values similar to the ones shown to the left. Once entered, click the Apply button. The final array should produce one row of 17 vertical lines.

4. Next draw a line between the start of the sound source and the bottom of the 10th line. This is best done in Front view (F7).
   
   This line is going to be the basis of our equal-sight-angle lines.
   
   We're using the 10th row back as the starting point for our rake, as the front seats will have good sight lines anyway.
   
   
5. Now, extend the line just created and the rear-most vertical line so that they meet .
   
   Select both the lines, then from the Modify menu choose the Intersect Two Lines item.
   
   
6. Finally you need to rotate the angled line by 1° about the speaker point.
   
   One of the easiest ways to do this is to; select the line, then select the Object Transformation panel. From the panel choose the Rotate - Axis from the Transform Type pull-down list, enter a Y Angle of 1° and an array quantity of about 20, then click the Create Array button.
   
   

Starting the Seating Profile

1. The next step is to zoom in to the first set of intersection points between the two sets of lines, and start tracing a new line where they intersect.
   
   Make sure snaps are set to Intersections, and that the Auditorium zone is current.
   
   As this line is the start of the seating profile it needs to be on a zone other than Construction Lines.
   
   
2. Continue this line through each of the vertical lines, all the way to the back of the audience plane.
   
   
3. Zoom out (Ctrl + F) and turn off the Construction Lines zone.
   
   The seating profile should look similar to the one shown below.
   
   

Creating Horizontal Steps

1. Zoom in on first raised node on the seating profile, double-click the line (Node mode) and select the first raised node.
   
   If the height of this node is less than 100mm then it needs to be dropped down to Z = 0, as it's not high enough to make a full step from.
   
   
   
   The easiest way to do this, is to enter 0 in the Z Position of the Selection Information panel, then click the Apply Changes button at the bottom of the panel.
2. Moving onto the next node... Still in Node mode, select the Add Node button.
   
   With Align snaps on (and preferably most of the other snaps off), left click the segment between the last node and the first raised node. Align the new node in the X and Y axis (as shown below), and left click again to accept the new nodes position.
   
   
3. Continue on adding and aligning new nodes, until the entire seating profile is modified from curved to stepped.
   
   The final curve should look like the one shown below. Given the step size towards the rear, you will probably have to model some additional steps in the aisles later on.
   
   
4. Before going on to the next section, double check the steps in perspective view.
   
   
   
   If your line looks like the one shown above, you will need to shift the new nodes in-line with the old.
   
   Again, the easiest way to do this is to select the nodes and use the Selection Information panel, and enter 4500 in the Y Position input box, as you did in step 1 of this section. Don't forget to click the Apply Changes button at the bottom of the panel.

Extruding a Line

Now that we have created the steps, we need to extrude them the full width of the auditorium.

1. With the line still selected and in Object mode, type 9000 in the Y Extrusion Vector box of the Selection Information panel. Then click the Apply Changes button at the bottom of the panel.
   
   
2. With the original object (now the parent object to all the extruded planes) still selected, use the Move tool to move the seating so that it lines up with the edge of the floor plane, -4500 in the Y axis.
   
   

Cutting and Shaping the Seating

It may not be desirable to have a rectangular seating area. In which case you can use a cutting plane to trim / extend the seating any way you want. As an example, we are going to cut it at an angle to the stage.

1. In Plan view, draw a Partition , from the speaker source point towards the rear of the seating at an angle of about 20°.
   
   
2. Assign the partition as a Cutting Plane (Ctrl+Q). A small arrow should appear in the centre of the object.
   
   Deselect the partition and instead select all of the seating planes.
   
   
   
   Once the seats are selected, press Ctrl+E to extend the selection to the Cutting Plane.
   
   
3. After one side has been extended, the same needs to be done for the other side.
   
   Either mirror the existing Cutting Plane about the centre, or create a new plane at -20°. Then repeat step 2, and when finished delete the one / two partition objects.
   
   The final seating should look similar to the image shown below.