A number of specialized soil utilities are available to help manipulate and monitor soil.

• The Soil Bin defines a container (truck bed, ship hold, storage bin, etc.) into which soil material can be poured. When soil material is present in the bin, it can also be dug into and removed.

• The Soil Layer is a versatile tool that can add soil within the bounds of an existing soil bin or earthwork zone. It is used to pre-fill soil bins, create soil piles and layers, and can also be used to bury items underground.

• The Soil Emitter, as its name implies, emits soil particles at a user-defined rate, with specific soil properties. It can be used to simulate a concrete bucket, for example.

• The Soil Culling Geometry can cull (erase) soil particles on contact. It is mostly used to simulate a drop zone, for example a hopper.

• The Soil Mass Sensor measures soil mass within certain boundaries. It is mostly used to measure spilled soil particles.

• The Soil Culling Monitor works only in conjunction with the Soil Culling Geometry, and measures soil mass that come into contact with it. It is mostly used to measure spilled soil particles.

• Special Deformable Soil Effects add extra visualization options for more soil information.

Soil Bin

The Soil Bin extension could be considered a sort of movable Earthwork Zone. It is used to simulate truck beds, ship holds, and any other construct that is intended to receive or contain soil. It is initially empty (though it can be pre-filled via the Soil Layer tool), and it supports soil dumping and digging (once soil has been deposited in it).

Before adding a Bucket extension to a mechanism, the latter should be first created with all the relevant parts, constraints and logic. Make sure that a part is created for the Soil Bin. The mechanism can be static or dynamic: a static mechanism must have all its parts set to the static control type. If the mechanism contains dynamic components, such as a vehicle system, collisions between these dynamic components and the Soil Bin extension must be disabled through collision rules.

When creating the collision geometries for the soil bin part, you can use primitives (such as boxes) to model the container. Those will be used for the interaction with other parts in the simulation, such as the bucket of the excavator. However, you will also need to create a separate triangle mesh collision geometry which represents the entire soil bin container, sidewalls and bottom included. This triangle mesh will be used later on to define the shape of the soil bin in the Soil Bin extension. To prevent any impact on simulation performance, you should disable collision detection with this triangle mesh by clearing any checkmark in the Enabled option under the Collision detection section of the collision geometry's Properties page.

To add a Soil Bin extension:

1. In your mechanism, select Earthwork Systems in the Toolbox.

2. Double-click Soil Bin to add one to your mechanism, or drag it into the 3D View.

A new folder with a Soil Bin icon appears under the mechanism in the Explorer Panel. It contains one dynamic extension and two graphic ones, plus a connection container; in the 3D View, you can now see their corresponding accessories.

• Dynamics Soil Bin: This extension defines the physical properties and shape of the Soil Bin extension.

• Graphics Soil: This extension controls the visual appearance of the soil contained within the Soil Bin extension.

• Graphics Particle Culling Box: This extension cull particles, emitted by the Particle Spray extension of a bucket, once they reach the bottom of the soil bin. This prevents visual particles from appearing below the soil bin.

• Connections: These are the data connections between the various components. They are set automatically.

After adding the soil bin to the mechanism, the next step is to link the soil bin's part to the dynamics extension and link the soil bin's graphic node to the graphics soil extension. Then the respective extensions are positioned in the mechanism (e.g., a dump truck) in order to accomplish their purposes. For example, the bounding box defined in the Dynamics Soil Bin extension needs to precisely fit in the body of the container which will receive the soil, e.g., the bed of a dump truck.

Attaching the Dynamics Soil Bin to the Soil Bin Part and Collision Geometries

From the Explorer panel, click the Dynamics Soil Bin extension under the Soil Bin folder. The Dynamics Soil Bin properties appear in the Properties panel.

Under the Parameters section:

1. Click the Browse button, then

   
   in the Bin Part reference field. The Select Soil Bin Part dialog box appears.

2. From the Explorer panel of your mechanism, go into the assembly, then locate and click on the part that you've set up for the soil bin of the mechanism.

3. The Soil Bin part's name appears in the Select Bin Part dialog box. Click the Confirm button.

4. The Soil Bin part's name now appears in the parameter box, and the accessory position is now relative to the soil bin part's origin.

5. Click the Browse button, then

   
   in the Bin CG reference field. The Select Bin CG dialog box appears.

6. From the Explorer panel of your mechanism, select the collision geometry which represents the entire soil bin geometry. Click the Confirm button.

The name of the collision geometry now appears in the Bin CG reference field.

Note The collision geometry specified as Bin CG is used by the extension to sample the soil bin container. It is mandatory that it represents the entire geometry of the soil bin container, therefore using a triangle mesh for this purpose is strongly advised. To prevent any impact on simulation performance, the triangle mesh can be disabled in the collision detection by clearing any check mark in the Enabled option under the Collision detection section of the collision geometry's properties.

Attaching the Soil Bin's Graphics Soil to the Soil Bin Node

From the Explorer panel, click the Graphics Soil entry under the Soil Bin folder. The Graphics Soil properties appears in the Properties panel.

1. Under the Parameters section, click the Browse

   
   button in the TerrainNode reference field. This nodes serves the same purpose as in the simple or generic bucket, that is, to sample the shape of the initially empty bucket. The Select TerrainNode dialog box appears.

2. From the Explorer panel of your mechanism, go into the Graphics Gallery, then locate and click on the graphic node of the soil bin.

3. The Soil Bin graphic node's name appears in the Select TerrainNode dialog box. Click the Confirm button.

The Soil Bin graphic node's name now appears in the parameter box and the Graphics Soil accessory box follows the soil bin's graphic node.

Configuring the Dynamics Soil Bin Extension

After connecting all the parts and nodes to the Soil Bin's extensions, you can see that the accessories are now clustered around the soil bin's origin.

The Dynamics Soil Bin extension's accessory is a colored box similar to the one defined on an Earthwork Zone. However, the soil bin accessory also provides four sets of parallel lines (green on one side, and red on the other) that act as guides as you position the accessory on the soil bin of the 3D model.

The outer lines define the boundary vertices of the dynamics height field, and the inner lines define the vertices which are adjacent to the boundary. They can be used as guiding aids during placement of the dynamics soil bin extension.

The red lines will always be perfectly aligned with the faces of the bounding box of the dynamics soil bin. The outermost red lines have to be placed exactly on the top of the side walls of the container which form the soil bin (e.g., the bed/box of a dump truck). The innermost red lines on the other hand have to be placed inside and on the bottom of the container (not on the side walls). This is to ensure that the outermost vertices of the height field are initially at a higher location than their adjacent inside vertices. When pouring soil into the soil bin, soil will then accumulate properly inside the bin and climb up until the height of the boundary vertices is reached.

After the red lines have been placed, the green lines need to be placed in an analogous way at the front and the back of the container. Note that due to the discrete nature of the dynamics height field which has square cells (that is, equally spaced vertices in local x and y direction), the green lines will not perfectly follow the faces of the bin's bounding box as is the case for the red lines. Instead they will jump from one place to another depending on the size of the box. This will make sure that cells in the dynamics height field always remain square. It is therefore easier to start fitting the red lines and fitting the green lines last, as the red lines will remain at their chosen location while placing the green lines.

From the Explorer panel, click the Dynamics Soil Bin entry under the Soil Bin folder. The Dynamics Soil Bin properties appear in the Properties panel.

• Local Transform: Modify these values to position the Dynamics Soil Bin accessory within the soil bin model. Alternatively, use the Move/Rotate manipulators in the 3D View to change the values.

• Parent Transform: Not used.

• Clear: If this input is selected, any soil present within the soil bin will be removed. This input can be used by a script to empty the soil bin at runtime.

• Shear Strength: Sets the shear strength of the soil within the Soil Bin, making it stronger or weaker. Reducing this value will make the soil slip easier, reducing the angle of repose. Also, less force will be needed to cut through the soil. See Shear Strength in Earthwork Zone for more.

• Flow Velocity Scale: Scales how fast the soil in the soil bin flows.

• World Transform: This is used to drive the graphic extensions. It is set automatically.

• Dimensions: Defines the dimensions of the soil bin, and is used to drive the Graphics Soil extension. It is set automatically.

• HeightField: This output is used to drive the Graphics Soil extension. It is set automatically.

• Particles: This output is used to drive the Graphics Soil extension. It is set automatically. The Mass output shows the mass of soil currently in the soil bin. It can be used by a script or displayed via a HUD.

• Parameters:

  • Material: This is the dynamics material assigned to the surface of the dynamics height field. Useful for tuning contact behavior when objects collide with the soil surface in the soil bin.

  • Bin Part: This is the part for the Soil Bin, that was attached in the previous step.

  • Bin CG: This is the collision geometry for the Soil Bin, that was attached in the previous step.

  • Dimensions: Modify these values to resize the Dynamics Soil Bin accessory to match the soil bin model. The Dynamics Soil Bin accessory should tightly wrap the soil bin part. The 3D Resize manipulator should always be used to modify this property.

  • Approximate Cell Size: This is the preferred size of the cells that divide the height field within the soil bin. See Cell Size in Earthwork Zone for more.

  • Spilling Enabled: If the field is deselected, the soil will remain in the soil bin. Note that this can cause unrealistically steep soil slopes at the soil bin's rim.

Note The accessory box has to be placed such that the boundary of the height field (outer rows and columns of vertices), marked by green and red lines, coincides with the sidewalls of the soil bin when seen from the top. The next rows and columns of vertices, marked by the inner set of green and red lines, should lie in the inside of the soil bin. It is possible, that the chosen approximate cell size has to be adapted to reach this configuration. The lines displayed in the Editor are meant to assist you in correctly placing the extension. The red lines will always lie exactly on the corresponding faces of the bounding box, while the green lines will perform jumps to produce square height field cells in the simulation. So, it is recommended to place the red lines first, and then place the green lines. This way, the already correctly placed red lines will not be affected by the manipulations done to place the green lines (resize of bounding box or refinement of approximate cell size). If you are having difficulty matching the dimensions of the accessory to the soil bin wall, try changing the Approximate Cell Size parameter and trying again. For example, decreasing the cell size will slightly narrow the gap between the inner and outer lines, making it easier to fit narrower soil bin walls.

Adding Collision Detection Rules to the Dynamics Soil Bin

When using the Dynamics Soil Bin extension with a dynamic vehicle, the extension requires additional collision detection rules to create a realistic and stable simulation.