Getting started with openPSTD v1.0
- Install openPSTD v1.0:
- Download … Thomas, kan je hier instructies geven?
- Now run Blender and from the [File] menu select [User Preferences] or click [Ctrl]+[Alt]+[U] to bring it up.
- Navigate to the [Addons] section and press the [Install from File...] button at the bottom of the window.
- Using the file selection prompt that shows up select the archive downloaded at step 2. Thomas, kan je dit updaten?
- Now enable the openPSTD add-on by ticking the checkbox on the right
- Every subsequent time to start Blender, you need to activate the openPSTD add-on by search for 'openPSTD' in the [Addons] section and ticking the checkbox
Drawing your first geometry in openPSTD v1.0
Creating the first subdomain
- Start Blender
- In order to begin modelling the scene clear all objects that appear in the default scene
- First deselect everything by pressing the [De(select) all] item from the [Select] menu
- Click the same item again to select everything
- Now click the [Delete...] item from the [Object] menu (If you do not see the [Object] menu either in the upper menu bar or in the lower menu bar, move your mouse pointer to the 3D view area and press [Tab] to switch from the Edit to the Object mode).
- Alternatively with the mouse over the 3D view area, press [A] [A] [X] [Enter]
- The Blender user interface relies heavily on keyboard shortcuts to allow for efficient modelling.
- Whenever a key is pressed make sure the mouse is over the relevant area. In this case the large 3D view area.
- Most operations in Blender triggered by the key strokes are also available from the menu items.
- Navigate to a viewpoint from above by selecting [Top] from the [View] menu (in the lower left corner of your screen)
- openPSTD v1.0 only supports 2D scenes.
- Create a planar mesh by activating [Plane] from the [Add] > [Mesh] menu.
- Alternatively bring up the same menu by clicking [Shift] + [A]
- Switch to metric display units by clicking on the [Scene] button, the third icon on the button strip at the right part of your screen, and select [Metric]
- Bring up the properties panel by clicking [View] > [Properties]
- Move your plane to the origin of the coordinate system by entering the location (x,y,z)=(1,1,0) in the [Location] part of the [Properties] toolbar. This plane is your first subdomain.
Modifying the first subdomain
- Change the dimensions of your plane using the [Dimensions] part of the [Transform] toolbar
- Edit the selected planar mesh by entering the Edit mode
- Alternatively click the [Tab] button to switch between Object mode and Edit mode
- Now, you can change the dimensions of your by changing the position of the edges as follows:
- Enter Edge select mode by clicking the appropriate button on the lower toolbar
- Select the rightmost edge by clicking it with the *right* mouse button
- Move the selected edge by *left* clicking the red arrow and typing 8 into the X field that appears on the left
Adding more subdomains
You can model your geometry by creating more subdomains as follows:
- Select the leftmost edge and press the [E] button ad press  [-] [Enter] to copy that edge 7 meters to the left
- Notice how the extrude operation is different from the move operation
- Now select the topleft edge
- Extrude that selected edge 7 meters by pressing the [E] [Y]  [Enter]
- Now select the two bottom edges by selecting the first and pressing [Shift] while selecting the second
- Move them down by by *left* clicking the green arrow and typing [-5] into the [Y] field that appears on the left
Multiple subdomains connected to one edge
So far, a geometry has been constructed out of subdomains, with all edges connected to two adjacent subdomains. It is important that the number of grid cells per subdomain (this number can be computed by the length of the subdomain size divided by the grid spacing value) is larger than the Window size (an explanation on this number can be found in openPSTD v1.0 settings). For this reason, a separate subdomain cannot be made above a thin object as a noise barrier (this incorrect geometry shown below). The geometry of the thin noise barrier can be constructed out of 4 subdomains. In the figure below, the upper left subdomain is wider than the lower left subdomain. A geometry as this can be obtained as follows:
- Create a geometry with two subdomains on top of each other.
- In the Edit mode, press the [Face select] icon on the toolbar below the 3D view area.
- Then, click the *right* mouse button when the mouse pointer is on the upper subdomain. Thereafter click [Y] and [Enter].
- Now, click [Edge select] on the lower toolbar and select the right edge of the upper subdomain.
- Enlarge it by clicking with the *left* mouse button on the horizontal red arrow.
- Enter 1 in the x-vector menu of the left toolbar en press [Enter]. You will see that the upper subdomain now is wider than the lower subdomain.
So far, the outer edges of our domain are assigned a default absorption coefficient, see openPSTD v1.0 settings for an explanation. The absorption coefficient can be changed as follows: Change the absorption coefficients of all surfaces. Navigate with the pointer to the center of the screen and press [Tab] to switch from the Object mode to the Edit mode (if you were not yet in the Edit mode). Now, navigate to a boundary of your geometry and select it by clicking it with the *right* mouse button. The [Shift] button may be used to select multiple sections. At the right of your screen (somewhere in the middle), click on the [Absorption 1.00] button. Enter the desired absorption value. All outer boundaries should get an absorption value of 1.00. The other boundaries (ground surface and barrier) should get lower values. For the barrier (as you have measured it), a value of 0 would be appropriate;
Sources and Receivers
Move lower left corner to origin. MaHo to extend text...
- Press [Tab] to exit Edit mode and enter Object mode to have the ability to add additional objects
- Press [Shift] + [A] and add a speaker object to the scene
- Note how the newly created object is positioned at where the cursor is located
- The location of the speaker can be set by using the [Location] part of the [Properties] toolbar
- Add an Empty object by using the same menu and define the location by altering the [Location] part of the [Properties] toolbar
- Any subtype of the Empty object would suffice
- Blender does not have a dedicated object to designate as a listener, therefore Empty objects are used in OpenPSTD
Prior to starting the simulation, please take care that the details of the computation are according to your wishes. These details can be found in the openPSTD settings menu in the part of your screen. Explanation on the settings can be found at openPSTD v1.0 settings.
Run a simulation
- Press the [Simulate with OpenPSTD] button
- Make sure that the "Python path" under [Show advanced settings] is setup correctly for the python executable (python.exe on Windows) to be found
- Make sure the planar mesh object is selected before pressing the button
- Notice how after a while areas for the subdomains appear
- Notice how the light gray area in the bottom area starts to grow over time. This represents the time steps for which a simulation result has been processed.
- Switch to textured viewport shading to have the sound pressure levels visually display in the 3D view
- Drag around within the light grey area timeline area and notice how the visualisation of sound pressure levels updates accordingly
- Stop the simulation by pressing the button on the OpenPSTD panel on the right
clear results ...
- Select the Empty object designated as the listener
- Notice how a depiction of the Impulse Response is drawn at the timeline area
- Use the rightmost button below that area to export the Impulse Response as a .wav file