To render simulations and use VSE, your development machine must include a compatible graphics card. The graphics card must support pixel and vertex shaders, but most laptops or desktop machines that are capable of running current graphics-based games will do this. Specifically, your graphics card must support the vertex shader VS_2_0 or higher and pixel shader PS_2_0 or higher. This means that the card must be compatible for DirectX version 9 or higher.

If you are not sure which of these shaders your graphics card uses and you have already installed MSRS, you can open one of the VSEs, such as the Basic Simulation Environment. Next, click on the Help menu, and then select About Microsoft Visual Simulation Environment (see Figure 4-2). If you scroll to the bottom of this dialog box, you will see what pixel and vertex shader versions your graphics card supports.

Tip

The following URL lists graphics cards that have been tested and approved by the MSRS team: http://channel9.msdn.com/wiki/default.aspx/Channel9.SimulationFAQ. Although this list does not include all graphics cards that may support VSE, it does cover some of the more commonly used ones. You can also check the following Web site to determine what pixel and vertex shaders your graphics card supports: http://www.techpowerup.com/gpudb/.

Figure 4-2. The About Microsoft Visual Simulation Environment dialog box displays information about which vertex and pixel shader versions the development machine is using.

It is possible to install MSRS on a development machine, work with services and the robotics tutorials, and still not be able to access VSE. One way to tell if your graphics card supports simulation is to install MSRS and try to run one of the simulations provided. If only the frame and menu bar of the VSE window appear, your card does not support the DirectX 9 shaders. You will either have to upgrade your graphics card or use a different development machine that does have a compatible graphics card.

It is also possible that your graphics card will not support the required shaders but will still try to render the scene. This is because there are two ways to perform graphics functions: by using software or by using hardware. If the functions are performed by the hardware, then the graphic will render very quickly. If the hardware does not support the graphics function, then the simulation will run in software mode. In general, software performs much more slowly than the hardware, and thus you may see significant performance degradation. To find out which shader versions your graphics card supports, refer to About Microsoft Visual Simulation Environment from the Help menu.

Using the AGEIA PhysX Card

MSRS uses the AGEIA PhysX engine to provide physics for the simulation environment. The MSRS installation contains the installation for the AGEIA PhysX engine, but you can optionally purchase and install the add-in hardware physics processor made by AGEIA. Although the AGEIA Web site (http://www.ageia.com) lists the price of the PhysX processor as $299 U.S. dollars, you can find it for much cheaper at local retailers such as Radio Shack or Fry’s Electronics. You can also buy it online through several retailers. I was able to buy a card for only $145 U.S. dollars through TigerDirect.com.

Tip

Depending on the complexity of the simulation you are running, you may not notice any differences in the simulation itself. Before running out and buying a PhysX card, I would suggest you work with the simulation tool and see if it meets your needs without the additional hardware purchase.

If you decide to purchase and install the card, keep the following in mind. Prior to installing the PhysX processor, you should see the following message in the command window when you start a simulation: "No physics hardware present, using software physics." This message will go away after you install the processor. You will also have access to additional properties in the AGEIA properties dialog box. You can access this dialog box through Start, Control Panel, and AGEIA PhysX. (If you are using Windows Vista, switch Control Panel to Classic View first, and then double-click AGEIA PhysX.) The Settings tab allows you to reset the AGEIA PhysX card and to start extended diagnostics. These functions will be available only if you have installed the card on your development machine.

Tracking the Frames per Second

VSE allows you to track the frames rendered per second using an optional status bar. The frames per second (FPS) setting is highly dependent on the capabilities of the graphics card and system capabilities of the development machine. It is also dependent on the number of entities and complexity of the objects within the simulation. The exact number of objects that you can add to a simulation depends on things such as the number of polygons used in those objects. A simple shape entity may have only a handful of polygons, but a more complex entity such as a robot may have thousands.

When using VSE to render a simulation, the FPS setting will be limited to the refresh rate for your monitor. Even if you were to upgrade your graphics card and install more memory, your simulation would not render faster than approximately 58 frames per second. The only exception to this would be if you disabled rendering and produced no visible image.

Note

You can see what refresh rate your monitor is using by opening the Display Settings dialog box and then clicking Advanced Settings. The Monitor tab lists the screen refresh rate, which is typically 59 Hertz for LCD monitors and 60 or more for CRT monitors.

If you were to run the simulation named "Basic Simulation Environment" (which is supplied with MSRS) and look at the FPS, you would see that it is close to 58 FPS. (You can view the FPS by choosing View, Status Bar, and then reviewing the contents of the Status Bar.) Alternatively, if you then were to run the simulation named "Simulation Environment with Terrain," you might see a drop in the FPS. Whether there would be a drop in FPS would depend on the type of graphics card you were using.

The terrain simulation (see Figure 4-3) includes numerous simply shaped objects such as spheres, boxes, and capsules. It also includes more complex objects such as tables, a robot, and even the terrain itself. To get an idea of how these objects are constructed, you can run the simulation and create a wireframe rendering using the Render menu item. The wireframe rendering shows the lines between all vertices but does not fill them in. This displays all the polygon shapes involved in forming the entity.

Figure 4-3. The Simulation Environment with Terrain, a simulation provided with MSRS, renders a variety of objects.

The only way to have the simulation run faster is to disable rendering by selecting the Render menu item and then selecting No Rendering. Even though you will not be able to see the rendered results, you could use the Log Messages feature from the simple dashboard service to record messages while controlling the simulated robot.

You can run a simulation and initiate VSE by executing DssNode and loading a manifest file that includes the simulation engine service. Recall from Chapter 2 that a manifest file provides a list of service contracts. These service contracts contain information that other services need to work with the target service. A manifest file that loads the simulation service will include a Partner node such as the following:

<Partner>         <Contract>http://schemas.microsoft.com/robotics/2006/04/simulationengine.html
</Contract>
<Service>IRobot.Create.Simulation.xml</Service>
<Name>StateService</Name>
</Partner>

Tip

If you want to see the contract information associated with the simulation service, you can use the DssInfo command from a DSS command prompt. This is done by accessing the Command Prompt from the Microsoft Robotics Studio menu and entering the following (assuming you are using MSRS, version 1.5):

DssInfo "C:Microsoft Robotics Studio (1.5)insimulationengine.proxy.dll"

This results in the listing of information about the service such as the service contract name and which PortSet operations are supported.

Alternatively, you can select Run Dss Node from the Microsoft Robotics Studio menu, which starts a DSS node and loads the System Services in an Internet browser window. You can then click Control Panel in the left pane and scroll to the Simulation Engine service. Clicking the link for that service displays the information in an Internet browser.

MSRS includes several simulations that you can find on the Microsoft Robotics Studio menu and in the Visual Simulation Environment folder. These simulations represent a variety of scenarios that demonstrate how to work with VSE and build simulations using the entity objects supplied with MSRS. The simulations included with MSRS 1.5 include the following:

Tip

KUKA provides access to additional tutorials that feature its robotic arms. Refer to the following URL for a listing of available tutorials, along with the source code: http://www.kuka.com/usa/en/products/software/educational_framework/. Readers interested in working with the KUKA arm should review the tutorials found on the KUKA Web site because they demonstrate the wide variety of capabilities for the multi-jointed robot.

Note

Even though the documentation that accompanies MSRS lists six simulation tutorials, the samplesSimulationTutorials directory contains directories for tutorials 1, 2, 4, and 5. There are also discrepancies between the simulations included in the MSRS menu item, the code available with the installation, and the help file included with MSRS.

When running a simulation, the first thing you notice is that an instance of the command window appears. The simulation uses the command window to start a DssNode and also to load one or more manifest files. This loads the simulation engine service and initiates VSE. By default, VSE starts the simulation in run mode and renders the scene as a solid 3D image. Alternatively, you could render the scene in a wireframe, physics, or a combined view. Because rendering of entities can be an expensive process when the scene involves a large number of entities, it is possible to turn rendering off.

Tip

If you encounter errors when trying to run any of the simulations provided with MSRS, open the solution file in Visual Studio and rebuild the solution. MSRS uses strong name signing, and it is possible for some services to be recompiled and for this to cause problems with other projects.

To see which files are associated with a simulation, click on the Start menu, All Programs, Microsoft Robotics Studio (1.5), and then Visual Simulation Environment. Right-click the icon for the simulation, and then choose Properties. The target should list all manifest files that are loaded for this simulation. There might be more than one manifest loaded, so you might have to recompile more than one solution. For example, the iRobot Create simulation loads two manifest files: IRobot.Create.Simulation.Manifest.xml and SimpleDashboard.manifest.xml.

Note that it might take a long time for some of the solution files to rebuild because they might contain several projects. Make sure the Visual Studio status bar states that the rebuild all was successful before attempting to run the simulation again.

MSRS provides a service that allows you to operate a variety of robotics hardware. The Simple Dashboard service initiates a Windows-based dialog box (see Figure 4-4) that allows you to connect to a DSS node and initiate one or more services running on that node. The dashboard appears automatically whenever you run a simulation that partners with the Simple Dashboard service. Most of the simulations provided with MSRS include the dashboard.

Figure 4-4. The Simple Dashboard service is one of the miscellaneous services offered with MSRS. This service initiates a Windows-based dialog box that allows you to control your physical or simulated robot.

Tip

When you run a simulation that includes the dashboard, the dashboard form will not receive focus and might be lost behind other windows running on your desktop. You might have to move the VSE window before you can see the dashboard form.

To connect to a DSS node on your local development machine, enter localhost in the Machine text box for the Dashboard dialog box. You then click Connect, and a list of services running on that node should appear in the list box below Service Directory. These services would have been loaded by the manifest file when you initiated the simulation. Depending on the service selected, you can perform the following functions:

Note

Although you can view messages as the simulation is running, the file size for a newly created log file remains at zero bytes until the simulation ends.

Enhanced Version of the Simple Dashboard Service

Because MSRS includes code for services such as the Simple Dashboard service, it is possible for you to extend the functionality available in these services. Ben Axelrod (see the following profile sidebar), a developer for Coroware (http://www.coroware.com) has released an enhanced version of the Simple Dashboard service (see Figure 4-5) that he makes available as a free download on his Web site (http://www.benaxelrod.com/MSRS/index.html). Be sure to put "MSRS" in all capital letters as this URL is case-sensitive.

Figure 4-5. An enhanced version of the Simple Dashboard service, available on Ben Axelrod’s Web site.

Profile: Ben Axelrod

For Ben Axelrod (see Figure 4-6), the drive to build robots began in early childhood, but it was not until high school, when his grandparents bought him a LEGO Mindstorms system, that his passion blossomed. At the age of 27, Axelrod has accomplished quite a lot in a field he almost missed out on.

Figure 4-6. Ben Axelrod, robotics developer for Coroware.

Two-time winner of the LEGO Mindstorms Novice Hall of Fame (http://mindstorms.lego.com/eng/inventions/default.asp), Axelrod has already held positions at Microsoft, Iguana Robotics Inc., and Coroware. In 2003 he graduated summa cum laude from Syracuse University in mechanical engineering and went on to earn a master’s degree in computer science from the Georgia Institute of Technology.

But it was Axelrod’s work with the LEGO Mindstorms that allowed him to see the world through the "eyes" of a robot. His inventions not only earned him the LEGO Hall of Fame distinction, but awakened a creative energy that has allowed him to work toward inspiring others to become roboticists.

When asked to speak about robots to a group of kids in Illinois, Axelrod went above and beyond the call of duty and produced a video that gives a realistic overview of the current world of robotics. The 10-minute video is available for download from Axelrod’s Web site through the following URL: http://www.benaxelrod.com/robotvideo/index.html. When asked why he likes talking to kids about robotics, Axelrod replied:

I almost missed the chance to be an engineer and roboticist. I just didn’t know that this was a possible career choice, and I want to show kids that this is possible. I also feel that engineering and computer science are very important jobs, and robotics is a great way to interest kids.

The enhanced Simple Dashboard service provides a few time-saving features, such as defaulting the localhost value for the machine name and removing the Drive and Stop buttons. The service also features many improvements to the Direct Input Device, which is used to drive robots with a differential drive system. The original dashboard service was limited to 60 percent power when using the joystick to drive the robot. The enhanced version allows you to drive the robot at 100 percent power and to control this using a slider control added to the dashboard form. In addition to controlling the robot with the mouse or joystick, you can use arrow keys on the keyboard.

Enhancements were also made to the laser rangefinder section, and the extended service features two views: a cylinder view and an overhead view. Green dots project the robot width forward, and red colored obstacles indicate objects directly in front of the robot.

Readers can use the enhanced dashboard by first downloading the zipped file from the following URL: http://www.benaxelrod.com/MSRS/index.html. Because the solution includes references to several projects that are available with MSRS, you should extract and store the contents of the downloaded file in the samplesmisc folder. The files available in the extracted folder should replace the files in the SimpleDashboard folder, which is already in the misc subfolder. Before replacing the contents of the SimpleDashboard folder, copy the original files to another folder.

After you copy the files to the correct location, you just need to open the solution file using Visual Studio and rebuild the solution. From this point on, whenever simulations involving the Simple Dashboard service are loaded, the enhanced version of the dashboard should appear.

Note

Because of strong name binding, you may have to rebuild some of the dependency projects, such as the SickLRF project. To do this, you will need to open the dependency project in Visual Studio and do a rebuild of this project before returning the SimpleDashboard solution file.

VSE allows you to modify graphics settings that will apply to multiple simulations. Although you can set additional settings using code in a DSS service, the graphics settings (see Figure 4-7) apply to commonly used settings such as the brightness or quality level of the scene. The graphics settings, which include the following, are accessible through the Render menu item:

Figure 4-7. The Graphics Settings dialog box provides access to commonly used settings that apply to multiple simulations.

You can also modify physics settings through the Physics menu item. The Physics settings allow you to control how the physics engine applies principles such as gravity. The gravity setting, which defaults to a value of 9.81, controls how the physics engine will handle gravity within the simulation scene. Typically, you will want to keep this setting as the default, but you may want to turn it off by setting it to a value of zero while making changes to the entities in edit mode.

Unless you have spent the last several years working intimately with vector maths and computer simulations, you may feel a bit overwhelmed by some of the terms and concepts used by the simulation engine. Do not worry about it too much. MSRS hides much of the complexity from you and acts as a wrapper for functions available in the Microsoft DirectX SDK, Microsoft XNA Framework, and AGEIA PhysX SDK. This section will give you a high-level overview of the things you need to understand when working with objects in 3D space.

To represent a physical object in 3D space, you must work with coordinates that represent the object’s position. These coordinates consist of points along the X, Y, and Z axis lines. The MSRS simulation engine uses what is known as a right-handed coordinate system. This affects which direction the positive Z-axis points in. Figure 4-8 is a diagram that indicates which direction the X, Y, and Z axis lines move toward. Lines moving in the opposite direction indicate points along the negative axis.

Figure 4-8. The simulation engine uses a right-handed coordinate system, which indicates the direction the positive Z-axis points toward.

When creating or editing entities, you will be able to edit the coordinates to change things such as the entity’s position. By changing the Y-axis coordinate to a higher positive value, the entity will move farther up in the simulation scene. If the value is set to a lower value, the entity moves farther down.

Tip

For readers interested in running a robot through a simulated maze, you can refer to a maze simulation tutorial hosted on Trevor Taylor’s Web site (http://sky.fit.qut.edu.au/~taylort2/MSRS/MazeSimulator/MazeSimulator.htm). Taylor is a faculty lecturer in the Information Technology department at the Queensland University of Technology. He is also an enthusiastic roboticist and MSRS expert, especially in the area of simulation. Check out his MSRS Web page at the following URL for more interesting information: http://sky.fit.qut.edu.au/~taylort2/MSRS/.

An entity represents a physical object that is used within a simulation. This can include, not only robots, but obstacles within the environment such as tables and chairs. It can also include ground and sky objects, and simulations can take place either in outdoor or indoor environments.

An entity can be hierarchical and involve parent and child relationships. This is the case when dealing with most robotics hardware where the motor base object represents the parent entity. Child entities would be the robot’s sensors and actuators. For example, the Pioneer 3DX simulated robot entity has three child entities: the bumpers, a laser rangefinder, and a Web camera.

Even the most basic simulations may contain a dozen or more entities. Complex simulations could involve hundreds or even thousands of entities. All simulations require a ground entity—unless you happen to be simulating robots floating in space. They will also require a sky object, but they do not require entities such as the sun or other elements that might appear in the sky. If the simulation is done indoors, it will typically be rendered inside a box, and you generally do not need to include things like light fixtures.

If you want to see the effect of numerous objects on a simulation, you can use one of the simulation tutorials and a Web browser to quickly add table objects to the simulation. To do this, you need to run Simulation Tutorial 2, which is available in the Visual Simulation Environment folder as the Multiple Simulated Robots simulation. When you first run this simulation, a table and two robots will appear in the simulation scene. While the simulation is running, open a Web browser and enter the following URL: http://localhost:50000/simulationtutorial2.

Your Web browser should display the state for the simulation in the form of XML. The state should contain a variable that indicates the number of tables in the simulation. If you continue to hit the refresh button in your Web browser, this number will increase by one, and tables will fall down from the sky onto the simulation scene (see Figure 4-9).

As additional entities are added to a simulation, it can cause the simulation to slow down and render at lower FPS. For this reason, you should try to limit the number of entities included in a simulation. MSRS includes several entity types (refer to Table 4-2 for a listing of these entity types) that you can use to build most of the entities you will need. The exception to this is robotics hardware not supported by MSRS and complex obstacles.

Tip

By default, the status bar is not displayed in VSE. To see the FPS settings, you will need to click on the View menu and then select Status Bar. The FPS setting will continually change even if nothing is changing within the simulation scene. This is due to things such as the refresh rate for your monitor and available CPU resources. The status bar also displays the simulation time, camera position, and Look At position.

Figure 4-9. Effect of adding multiple table objects to Simulation Tutorial 2 using a Web browser.

To create a new entity in VSE, you must be in edit mode within the simulation environment. While in edit mode, the top-left pane will display all of the entities that currently appear in the simulation scene. When you select an item, the properties for that entity appear in the bottom-left pane. Table 4-1 lists the basic properties available for an entity.

Depending on the type of entity, there may be additional properties available. For example, an entity representing the Pioneer 3DX robot will include a property named MotorTorqueScaling, which is used to set a scaling factor that applies to all motor torque requests. Obviously, this is a property that would have no use for a sky entity. A sky entity does, however, have use for properties related to fog, such as the fog color.

While in edit mode, hold down the Ctrl key to see which entity is selected. The selected entity will appear with a circle surrounding it, as shown previously in Figure 4-1. You can then use the arrow keys to move the main camera around the object as it is zoomed in. This allows you to see all sides of the object clearly. For example, Figure 4-10 shows a close-up of the rear view for the LEGO NXT. You can also use the Ctrl key and mouse to change the entity’s position or rotation. This is done by selecting the object in edit mode and also selecting the position or rotation property. While you hold down the Ctrl key, use the mouse to move or rotate the entity.

Figure 4-10. Using the Ctrl and arrow keys, you can focus in on a selected entity and view all sides such as the rear view of the LEGO NXT.

To create a new entity, click on the Entity menu, and then select New. This brings up the New Entity dialog box (see Figure 4-11) and allows you to define a new entity. The entity can be added to either the current simulation or to another assembly. An entity type (see Table 4-2 for a list of available entity types) must be selected. The entity type acts as a template for an entity and, thus, assigns initial property values for a new entity.

Figure 4-11. While in edit mode, the New Entity dialog box is used to add new entities to a simulation scene.

Table 4-3 lists the basic properties available when you select the ellipses next to the EntityState property. Depending on what type of entity it is, the properties that appear might be slightly different. These properties control both how the entity appears when rendered and how it behaves in relation to the physics engine.

When setting the properties listed in Table 4-3, consider that MSRS represents distance in terms of meters and weight in terms of kilograms. In case you do not remember, 1 meter equals 1.093 yards or 39.37 inches. Alternatively, 1 yard equals .0914 meters or 36 inches. If you want to compute the distance of an entity in meters, you could multiply the number of yards by .0914. If you only knew the number of inches, you could multiply the number of inches by .0254. Both calculations should give you a value in meters.

Also, 1 kilogram equals 1,000 grams, and 453.59 grams equals 16 ounces or 1 pound. If you want to compute the weight in kilograms of an object weighing 3 pounds, you would first need to multiply the number of pounds by 453.59 (3 * 453.59) to arrive at a value of 1,360.77. To get the number of kilograms, divide that number by 1,000 (1360.77 / 1,000) to arrive at a value of 1.36. This would be the value you would set for the approximate number of kilograms needed to represent 3 pounds.

The values associated with the state of an entity will change as the simulation is running. For example, the robot’s position will be determined by the X, Y, and Z coordinate values set for the position property. The initial values set for this property will change as the robot is driven around the simulation scene. You can see this for yourself by running a simulation, such as the iRobot Create simulation, and switching into edit mode. Initially, the position of the Create robot is set with the following coordinate values: 2, 0, 0. If you switch back to run mode and use the Simple Dashboard to move the Create robot, you would find that the position values have changed when you return to edit mode.

VSE allows you to save simulation scenes by clicking on File and then selecting Save Scene As. This will create two XML-based files: one is a manifest file and will contain a list of service contacts that need to be loaded to run the simulation. The other file contains information about the state of the simulator and the entities that exist within the simulation scene.

The simulator state file is a snapshot of what the simulation looked like at an exact point in time. The information within this file can be useful for many purposes. While learning about simulation and the numerous properties available for each entity, it can be helpful to browse through the simulator state file and see what values are associated with each property. For example, the following XML is only a portion of the state associated with a single-shape entity named greybox:

<BoxShape>
 <phys:BoxState>
   <phys:Name>greybox</phys:Name>
   <phys:ShapeId>Box</phys:ShapeId>
   <phys:Dimensions>
     <physm:X>1</physm:X>
     <physm:Y>1.5</physm:Y>
     <physm:Z>0.5</physm:Z>
   </phys:Dimensions>
   <phys:Radius>0</phys:Radius>
   <phys:Material>
     <phys:Name>gbox</phys:Name>
     <phys:Restitution>0.5</phys:Restitution>
     <phys:DynamicFriction>0.4</phys:DynamicFriction>
     <phys:StaticFriction>0.5</phys:StaticFriction>
     <phys:MaterialIndex>2</phys:MaterialIndex>
   </phys:Material>
   <phys:MassDensity>
     <phys:Mass>10</phys:Mass>
     <phys:InertiaTensor>
       <physm:X>0</physm:X>
       <physm:Y>0</physm:Y>
       <physm:Z>0</physm:Z>
     </phys:InertiaTensor>
     <phys:CenterOfMass>
   <physm:Position>
         <physm:X>0</physm:X>
         <physm:Y>0</physm:Y>
         <physm:Z>0</physm:Z>
       </physm:Position>
       <physm:Orientation>
         <physm:X>0</physm:X>
         <physm:Y>0</physm:Y>
         <physm:Z>0</physm:Z>
         <physm:W>0</physm:W>
       </physm:Orientation>
     </phys:CenterOfMass>
     <phys:Density>0</phys:Density>
     <phys:LinearDamping>0</phys:LinearDamping>
     <phys:AngularDamping>0</phys:AngularDamping>
   </phys:MassDensity>
   <phys:LocalPose>
     <physm:Position>
       <physm:X>0</physm:X>
       <physm:Y>0</physm:Y>
       <physm:Z>0</physm:Z>
     </physm:Position>
     <physm:Orientation>
       <physm:X>0</physm:X>
       <physm:Y>0</physm:Y>
       <physm:Z>0</physm:Z>
       <physm:W>1</physm:W>
     </physm:Orientation>
   </phys:LocalPose>
   <phys:TextureFileName />
   <phys:DiffuseColor>
     <physm:X>0.5</physm:X>
     <physm:Y>0.5</physm:Y>
     <physm:Z>0.5</physm:Z>
     <physm:W>1</physm:W>
   </phys:DiffuseColor>
   <phys:EnableContactNotifications>false</phys:EnableContactNotifications>
 </phys:BoxState>
</BoxShape>

In addition to gathering information about the entities used in a simulation, the simulation state file can be useful when there is a need to quickly edit properties or add new entities. After you make changes to a simulation state file, use the File and Open Scene menu items to reload the changes into VSE.