Modelica.Mechanics.MultiBody.Visualizers

Information

Package Visualizers contains components to visualize 3-dimensional shapes. These components are the basis for the animation features of the MultiBody library.

Content

FixedShape FixedShape2	Animation shape of a part with fixed sizes. FixedShape2 has additionally a frame_b for easier connection to further visual objects. The following shape types are supported:
FixedFrame	Visualizing a coordinate system including axes labels with fixed sizes:
FixedArrow, SignalArrow	Visualizing an arrow. Model "FixedArrow" provides a fixed sized arrow, model "SignalArrow" provides an arrow with dynamically varying length that is defined by an input signal vector:
Advanced	Package that contains components to visualize 3-dimensional shapes where all parts of the shape can vary dynamically. Basic knowledge of Modelica is needed in order to utilize the components of this package.

The colors of the visualization components are declared with the predefined type MultiBody.Types.Color. This is a vector with 3 elements, {r, g, b}, and specifies the color of the shape. {r,g,b} are the "red", "green" and "blue" color parts. Note, r g, b are given as Integer[3] in the ranges 0 .. 255, respectively.

Extends from Modelica.Icons.Library (Icon for library).

Package Content

Name	Description
FixedShape	Animation shape of a part with fixed shape type and dynamically varying shape definition
FixedShape2	Animation shape of a part with fixed shape type and dynamically varying shape definition with two frames
FixedFrame	Visualizing a coordinate system including axes labels (visualization data may vary dynamically)
FixedArrow	Visualizing an arrow with dynamically varying size in frame_a
SignalArrow	Visualizing an arrow with dynamically varying size in frame_a based on input signal
Ground	Visualize ground (box in z=0)
Advanced	Visualizers that require basic knowledge about Modelica in order to use them
Internal	Visualizers that will be replaced by improved versions in the future (don't use them)

Modelica.Mechanics.MultiBody.Visualizers.FixedShape

Information

Model FixedShape defines a visual shape that is shown at the location of its frame_a. All describing data such as size and color can vary dynamically by providing appropriate expressions in the input fields of the parameter menu. The only exception is parameter shapeType that cannot be changed during simulation. The following shapes are currently supported via parameter shapeType (e.g., shapeType="box"):
 

 
The dark blue arrows in the figure above are directed along variable lengthDirection. The light blue arrows are directed along variable widthDirection. The coordinate systems in the figure represent frame_a of the FixedShape component.

Additionally external shapes are specified as DXF-files (only 3-dim.Face is supported). External shapes must be named "1", "2" etc.. The corresponding definitions should be in files "1.dxf", "2.dxf" etc.Since the DXF-files contain color and dimensions for the individual faces, the corresponding information in the model is currently ignored. The DXF-files must be found in the current directory.

The sizes of any of the above components are specified by the length, width and height variables. Via variable extra additional data can be defined:

Parameter color is a vector with 3 elements, {r, g, b}, and specifies the color of the shape. {r,g,b} are the "red", "green" and "blue" color parts. Note, r g, b are given as Integer[3] in the ranges 0 .. 255, respectively. The predefined type MultiBody.Types.Color contains a temporary menu definition of the colors used in the MultiBody library (this will be replaced by a color editor).

Extends from Modelica.Mechanics.MultiBody.Interfaces.PartialVisualizer (Base model for visualizers (has a frame_a on the left side + outer world + assert to guarantee that the component is connected)).

Parameters

Type	Name	Default	Description
Boolean	animation	true	= true, if animation shall be enabled
if animation = true
ShapeType	shapeType	"box"	Type of shape
Position	r_shape[3]	{0,0,0}	Vector from frame_a to shape origin, resolved in frame_a [m]
Axis	lengthDirection	{1,0,0}	Vector in length direction of shape, resolved in frame_a [1]
Axis	widthDirection	{0,1,0}	Vector in width direction of shape, resolved in frame_a [1]
Distance	length		Length of shape [m]
Distance	width		Width of shape [m]
Distance	height		Height of shape [m]
Color	color	{0,128,255}	Color of shape
ShapeExtra	extra	0.0	Additional data for cylinder, cone, pipe, gearwheel and spring
SpecularCoefficient	specularCoefficient	world.defaultSpecularCoeffic...	Reflection of ambient light (= 0: light is completely absorbed)

Connectors

Type	Name	Description
Frame_a	frame_a	Coordinate system in which visualization data is resolved

Modelica definition

model FixedShape 
  "Animation shape of a part with fixed shape type and dynamically varying shape definition"
  import SI = Modelica.SIunits;
  import Modelica.Mechanics.MultiBody.Types;
  extends Modelica.Mechanics.MultiBody.Interfaces.PartialVisualizer;

  parameter Boolean animation=true "= true, if animation shall be enabled";
  parameter Types.ShapeType shapeType="box" "Type of shape";
  input SI.Position r_shape[3]={0,0,0} 
    "Vector from frame_a to shape origin, resolved in frame_a";
  input Types.Axis lengthDirection={1,0,0} 
    "Vector in length direction of shape, resolved in frame_a";
  input Types.Axis widthDirection={0,1,0} 
    "Vector in width direction of shape, resolved in frame_a";
  input SI.Distance length(start=1) "Length of shape";
  input SI.Distance width(start=0.1) "Width of shape";
  input SI.Distance height(start=0.1) "Height of shape";
  input Modelica.Mechanics.MultiBody.Types.Color color={0,128,255} 
    "Color of shape";
  input Types.ShapeExtra extra=0.0 
    "Additional data for cylinder, cone, pipe, gearwheel and spring";
  input Types.SpecularCoefficient specularCoefficient = world.defaultSpecularCoefficient 
    "Reflection of ambient light (= 0: light is completely absorbed)";

protected 
  Advanced.Shape vis(
    shapeType=shapeType,
    r_shape=r_shape,
    lengthDirection=lengthDirection,
    widthDirection=widthDirection,
    length=length,
    width=width,
    height=height,
    color=color,
    extra=extra,
    specularCoefficient=specularCoefficient,
    r=frame_a.r_0,
    R=frame_a.R) if world.enableAnimation and animation;
equation 
  // No forces and torques
  frame_a.f = zeros(3);
  frame_a.t = zeros(3);
end FixedShape;

Modelica.Mechanics.MultiBody.Visualizers.FixedShape2

Information

Model FixedShape2 defines a visual shape that is shown at the location of its frame_a. This model is identical to FixedShape with the only difference that an additional frame_b is present which is parallel to frame_a. This makes it more convenient to connect several visual shapes together when building up more complex visual objects. All describing data such as size and color can vary dynamically by providing appropriate expressions in the input fields of the parameter menu. The only exception is parameter shapeType that cannot be changed during simulation. The following shapes are currently supported via parameter shapeType (e.g., shapeType="box"):
 

 
The dark blue arrows in the figure above are directed along variable lengthDirection. The light blue arrows are directed along variable widthDirection. The coordinate systems in the figure represent frame_a of the FixedShape component.

Additionally external shapes are specified as DXF-files (only 3-dim.Face is supported). External shapes must be named "1", "2" etc.. The corresponding definitions should be in files "1.dxf", "2.dxf" etc.Since the DXF-files contain color and dimensions for the individual faces, the corresponding information in the model is currently ignored. The DXF-files must be found in the current directory.

The sizes of any of the above components are specified by the length, width and height variables. Via variable extra additional data can be defined:

Parameter color is a vector with 3 elements, {r, g, b}, and specifies the color of the shape. {r,g,b} are the "red", "green" and "blue" color parts. Note, r g, b are given as Integer[3] in the ranges 0 .. 255, respectively. The predefined type MultiBody.Types.Color contains a temporary menu definition of the colors used in the MultiBody library (this will be replaced by a color editor).

In the following figure the relationships between frame_a and frame_b are shown. The origin of frame_b with respect to frame_a is specified via parameter vector r.

Parameters

Type	Name	Default	Description
Boolean	animation	true	= true, if animation shall be enabled
if animation = true
ShapeType	shapeType	"box"	Type of shape
Position	r_shape[3]	{0,0,0}	Vector from frame_a to shape origin, resolved in frame_a [m]
Axis	lengthDirection	r - r_shape	Vector in length direction of shape, resolved in frame_a [1]
Axis	widthDirection	{0,1,0}	Vector in width direction of shape, resolved in frame_a [1]
Length	length	Modelica.Math.Vectors.length...	Length of shape [m]
Distance	width	0.1	Width of shape [m]
Distance	height	width	Height of shape [m]
ShapeExtra	extra	0.0	Additional data for cylinder, cone, pipe, gearwheel and spring
Color	color	{0,128,255}	Color of shape
SpecularCoefficient	specularCoefficient	world.defaultSpecularCoeffic...	Reflection of ambient light (= 0: light is completely absorbed)

Connectors

Type	Name	Description
Frame_a	frame_a	Coordinate system a (all shape definition vectors are resolved in this frame)
Frame_b	frame_b	Coordinate system b

Modelica definition

model FixedShape2 
  "Animation shape of a part with fixed shape type and dynamically varying shape definition with two frames"

  import SI = Modelica.SIunits;
  import Modelica.Mechanics.MultiBody.Frames;
  import Modelica.Mechanics.MultiBody.Types;

  Interfaces.Frame_a frame_a 
    "Coordinate system a (all shape definition vectors are resolved in this frame)";
  Interfaces.Frame_b frame_b "Coordinate system b";

  parameter Boolean animation=true "= true, if animation shall be enabled";
  parameter Types.ShapeType shapeType="box" "Type of shape";
  input SI.Position r[3]={1,0,0} 
    "Vector from frame_a to frame_b resolved in frame_a";
  input SI.Position r_shape[3]={0,0,0} 
    "Vector from frame_a to shape origin, resolved in frame_a";
  input Types.Axis lengthDirection=r - r_shape 
    "Vector in length direction of shape, resolved in frame_a";
  input Types.Axis widthDirection={0,1,0} 
    "Vector in width direction of shape, resolved in frame_a";
  input SI.Length length=Modelica.Math.Vectors.length(
                                       r - r_shape) "Length of shape";
  input SI.Distance width=0.1 "Width of shape";
  input SI.Distance height=width "Height of shape";
  input Types.ShapeExtra extra=0.0 
    "Additional data for cylinder, cone, pipe, gearwheel and spring";
  input Types.Color color={0,128,255} "Color of shape";
  input Types.SpecularCoefficient specularCoefficient = world.defaultSpecularCoefficient 
    "Reflection of ambient light (= 0: light is completely absorbed)";

protected 
  outer MultiBody.World world;
  Advanced.Shape shape(
    shapeType=shapeType,
    r_shape=r_shape,
    lengthDirection=lengthDirection,
    widthDirection=widthDirection,
    length=length,
    width=width,
    height=height,
    extra=extra,
    color=color,
    specularCoefficient = specularCoefficient,
    r=frame_a.r_0,
    R=frame_a.R) if world.enableAnimation and animation;
equation 
  Connections.branch(frame_a.R, frame_b.R);
  assert(cardinality(frame_a) > 0 or cardinality(frame_b) > 0, "Neither connector frame_a nor frame_b of
MultiBody.Visualizers.FixedShape2 object is connected");

  frame_b.r_0 = frame_a.r_0 + Frames.resolve1(frame_a.R, r);
  frame_b.R = frame_a.R;

  /* Force and torque balance */
  zeros(3) = frame_a.f + frame_b.f;
  zeros(3) = frame_a.t + frame_b.t + cross(r, frame_b.f);
end FixedShape2;

Modelica.Mechanics.MultiBody.Visualizers.FixedFrame

Information

Model FixedFrame visualizes the three axes of its coordinate system frame_a together with appropriate axes labels. A typical example is shown in the following figure:
 

The sizes of the axes, the axes colors and the specular coefficient (= reflection factor for ambient light) can vary dynamically by providing appropriate expressions in the input fields of the parameter menu.

Extends from Modelica.Mechanics.MultiBody.Interfaces.PartialVisualizer (Base model for visualizers (has a frame_a on the left side + outer world + assert to guarantee that the component is connected)).

Parameters

Type	Name	Default	Description
Boolean	animation	true	= true, if animation shall be enabled
if animation = true
Boolean	showLabels	true	= true, if labels shall be shown
Distance	length	0.5	Length of axes arrows [m]
Distance	diameter	length/world.defaultFrameDia...	Diameter of axes arrows [m]
Color	color_x	Modelica.Mechanics.MultiBody...	Color of x-arrow
Color	color_y	color_x	Color of y-arrow
Color	color_z	color_x	Color of z-arrow
SpecularCoefficient	specularCoefficient	world.defaultSpecularCoeffic...	Reflection of ambient light (= 0: light is completely absorbed)

Connectors

Type	Name	Description
Frame_a	frame_a	Coordinate system in which visualization data is resolved

Modelica definition

model FixedFrame 
  "Visualizing a coordinate system including axes labels (visualization data may vary dynamically)"

  import SI = Modelica.SIunits;
  import Modelica.Mechanics.MultiBody.Types;
  extends Modelica.Mechanics.MultiBody.Interfaces.PartialVisualizer;
  parameter Boolean animation=true "= true, if animation shall be enabled";
  parameter Boolean showLabels=true "= true, if labels shall be shown";
  input SI.Distance length=0.5 "Length of axes arrows";
  input SI.Distance diameter=length/world.defaultFrameDiameterFraction 
    "Diameter of axes arrows";
  input Types.Color color_x=Modelica.Mechanics.MultiBody.Types.Defaults.
      FrameColor "Color of x-arrow";
  input Types.Color color_y=color_x "Color of y-arrow";
  input Types.Color color_z=color_x "Color of z-arrow";
  input Types.SpecularCoefficient specularCoefficient = world.defaultSpecularCoefficient 
    "Reflection of ambient light (= 0: light is completely absorbed)";
protected 
  parameter Boolean animation2 = world.enableAnimation and animation;
  parameter Boolean showLabels2= world.enableAnimation and animation and showLabels;

  // Parameters to define axes
  SI.Length headLength=min(length, diameter*Types.Defaults.FrameHeadLengthFraction);
  SI.Length headWidth=diameter*Types.Defaults.FrameHeadWidthFraction;
  SI.Length lineLength=max(0, length - headLength);
  SI.Length lineWidth=diameter;

  // Parameters to define axes labels
  SI.Length scaledLabel=Modelica.Mechanics.MultiBody.Types.Defaults.FrameLabelHeightFraction*diameter;
  SI.Length labelStart=1.05*length;

  // x-axis
  Visualizers.Advanced.Shape x_arrowLine(
    shapeType="cylinder",
    length=lineLength,
    width=lineWidth,
    height=lineWidth,
    lengthDirection={1,0,0},
    widthDirection={0,1,0},
    color=color_x,
    specularCoefficient=specularCoefficient,
    r=frame_a.r_0,
    R=frame_a.R) if animation2;
  Visualizers.Advanced.Shape x_arrowHead(
    shapeType="cone",
    length=headLength,
    width=headWidth,
    height=headWidth,
    lengthDirection={1,0,0},
    widthDirection={0,1,0},
    color=color_x,
    specularCoefficient=specularCoefficient,
    r=frame_a.r_0 + Frames.resolve1(frame_a.R, {lineLength,0,0}),
    R=frame_a.R) if animation2;
  Visualizers.Internal.Lines x_label(
    lines=scaledLabel*{[0, 0; 1, 1],[0, 1; 1, 0]},
    diameter=diameter,
    color=color_x,
    specularCoefficient=specularCoefficient,
    r_lines={labelStart,0,0},
    n_x={1,0,0},
    n_y={0,1,0},
    r=frame_a.r_0,
    R=frame_a.R) if showLabels2;

  // y-axis
  Visualizers.Advanced.Shape y_arrowLine(
    shapeType="cylinder",
    length=lineLength,
    width=lineWidth,
    height=lineWidth,
    lengthDirection={0,1,0},
    widthDirection={1,0,0},
    color=color_y,
    specularCoefficient=specularCoefficient,
    r=frame_a.r_0,
    R=frame_a.R) if animation2;
  Visualizers.Advanced.Shape y_arrowHead(
    shapeType="cone",
    length=headLength,
    width=headWidth,
    height=headWidth,
    lengthDirection={0,1,0},
    widthDirection={1,0,0},
    color=color_y,
    specularCoefficient=specularCoefficient,
    r=frame_a.r_0 + Frames.resolve1(frame_a.R, {0,lineLength,0}),
    R=frame_a.R) if animation2;
  Visualizers.Internal.Lines y_label(
    lines=scaledLabel*{[0, 0; 1, 1.5],[0, 1.5; 0.5, 0.75]},
    diameter=diameter,
    color=color_y,
    specularCoefficient=specularCoefficient,
    r_lines={0,labelStart,0},
    n_x={0,1,0},
    n_y={-1,0,0},
    r=frame_a.r_0,
    R=frame_a.R) if showLabels2;

  // z-axis
  Visualizers.Advanced.Shape z_arrowLine(
    shapeType="cylinder",
    length=lineLength,
    width=lineWidth,
    height=lineWidth,
    lengthDirection={0,0,1},
    widthDirection={0,1,0},
    color=color_z,
    specularCoefficient=specularCoefficient,
    r=frame_a.r_0,
    R=frame_a.R) if animation2;
  Visualizers.Advanced.Shape z_arrowHead(
    shapeType="cone",
    length=headLength,
    width=headWidth,
    height=headWidth,
    lengthDirection={0,0,1},
    widthDirection={0,1,0},
    color=color_z,
    specularCoefficient=specularCoefficient,
    r=frame_a.r_0 + Frames.resolve1(frame_a.R, {0,0,lineLength}),
    R=frame_a.R) if animation2;
  Visualizers.Internal.Lines z_label(
    lines=scaledLabel*{[0, 0; 1, 0],[0, 1; 1, 1],[0, 1; 1, 0]},
    diameter=diameter,
    color=color_z,
    specularCoefficient=specularCoefficient,
    r_lines={0,0,labelStart},
    n_x={0,0,1},
    n_y={0,1,0},
    r=frame_a.r_0,
    R=frame_a.R) if showLabels2;
equation 
  frame_a.f = zeros(3);
  frame_a.t = zeros(3);
end FixedFrame;

Modelica.Mechanics.MultiBody.Visualizers.FixedArrow

Information

Model FixedArrow defines an arrow that is shown at the location of its frame_a.
 

The direction of the arrow specified with vector n is with respect to frame_a, i.e., the local frame to which the arrow component is attached. The direction and length of the arrow, its diameter and color can vary dynamically by providing appropriate expressions in the input fields of the parameter menu.

Extends from Modelica.Mechanics.MultiBody.Interfaces.PartialVisualizer (Base model for visualizers (has a frame_a on the left side + outer world + assert to guarantee that the component is connected)).

Parameters

Type	Name	Default	Description
Boolean	animation	true	= true, if animation shall be enabled
if animation = true
Position	r_tail[3]	{0,0,0}	Vector from frame_a to arrow tail, resolved in frame_a [m]
Axis	n	{1,0,0}	Vector in arrow direction, resolved in frame_a [1]
Length	length	0.1	Length of complete arrow [m]
Diameter	diameter	world.defaultArrowDiameter	Diameter of arrow line [m]
Color	color	{0,0,255}	Color of arrow
SpecularCoefficient	specularCoefficient	world.defaultSpecularCoeffic...	Reflection of ambient light (= 0: light is completely absorbed)

Connectors

Type	Name	Description
Frame_a	frame_a	Coordinate system in which visualization data is resolved

Modelica definition

model FixedArrow 
  "Visualizing an arrow with dynamically varying size in frame_a"

  import SI = Modelica.SIunits;
  import Modelica.Mechanics.MultiBody.Types;
  extends Modelica.Mechanics.MultiBody.Interfaces.PartialVisualizer;
  parameter Boolean animation=true "= true, if animation shall be enabled";
  input SI.Position r_tail[3]={0,0,0} 
    " Vector from frame_a to arrow tail, resolved in frame_a";
  input Types.Axis n={1,0,0} " Vector in arrow direction, resolved in frame_a";
  input SI.Length length=0.1 " Length of complete arrow";
  input SI.Diameter diameter=world.defaultArrowDiameter 
    " Diameter of arrow line";
  input Types.Color color={0,0,255} " Color of arrow";
  input Types.SpecularCoefficient specularCoefficient = world.defaultSpecularCoefficient 
    "Reflection of ambient light (= 0: light is completely absorbed)";
protected 
  SI.Length headLength=min(length, diameter*Types.Defaults.
      ArrowHeadLengthFraction);
  SI.Length headWidth=diameter*Types.Defaults.
      ArrowHeadWidthFraction;
  SI.Length lineLength=max(0, length - headLength);
  Visualizers.Advanced.Shape arrowLine(
    shapeType="cylinder",
    length=lineLength,
    width=diameter,
    height=diameter,
    lengthDirection=n,
    widthDirection={0,1,0},
    color=color,
    specularCoefficient=specularCoefficient,
    r_shape=r_tail,
    r=frame_a.r_0,
    R=frame_a.R) if world.enableAnimation and animation;
  Visualizers.Advanced.Shape arrowHead(
    shapeType="cone",
    length=headLength,
    width=headWidth,
    height=headWidth,
    lengthDirection=n,
    widthDirection={0,1,0},
    color=color,
    specularCoefficient=specularCoefficient,
    r_shape=r_tail + Modelica.Math.Vectors.normalize(
                                      n)*lineLength,
    r=frame_a.r_0,
    R=frame_a.R) if world.enableAnimation and animation;

equation 
  frame_a.f = zeros(3);
  frame_a.t = zeros(3);

end FixedArrow;

Modelica.Mechanics.MultiBody.Visualizers.SignalArrow

Information

Model SignalArrow defines an arrow that is dynamically visualized at the location where its frame_a is attached. The position vector from the tail to the head of the arrow, resolved in frame_a, is defined via the signal vector of the connector r_head (Real r_head[3]):
 

The tail of the arrow is defined with parameter r_tail with respect to frame_a (vector from the origin of frame_a to the arrow tail).

Extends from Modelica.Mechanics.MultiBody.Interfaces.PartialVisualizer (Base model for visualizers (has a frame_a on the left side + outer world + assert to guarantee that the component is connected)).

Parameters

Type	Name	Default	Description
Boolean	animation	true	= true, if animation shall be enabled
if animation = true
Position	r_tail[3]	{0,0,0}	Vector from frame_a to arrow tail, resolved in frame_a [m]
Diameter	diameter	world.defaultArrowDiameter	Diameter of arrow line [m]
Color	color	{0,0,255}	Color of arrow
SpecularCoefficient	specularCoefficient	world.defaultSpecularCoeffic...	Reflection of ambient light (= 0: light is completely absorbed)

Connectors

Type	Name	Description
Frame_a	frame_a	Coordinate system in which visualization data is resolved
input RealInput	r_head[3]	Position vector from origin of frame_a to head of arrow, resolved in frame_a [m]

Modelica definition

model SignalArrow 
  "Visualizing an arrow with dynamically varying size in frame_a based on input signal"

  import SI = Modelica.SIunits;
  import Modelica.Mechanics.MultiBody.Types;

  extends Modelica.Mechanics.MultiBody.Interfaces.PartialVisualizer;
  parameter Boolean animation=true "= true, if animation shall be enabled";
  input SI.Position r_tail[3]={0,0,0} 
    "Vector from frame_a to arrow tail, resolved in frame_a";
  input SI.Diameter diameter=world.defaultArrowDiameter 
    "Diameter of arrow line";
  input Modelica.Mechanics.MultiBody.Types.Color color={0,0,255} 
    "Color of arrow";
  input Types.SpecularCoefficient specularCoefficient = world.defaultSpecularCoefficient 
    "Reflection of ambient light (= 0: light is completely absorbed)";

  Modelica.Blocks.Interfaces.RealInput r_head[3](each final quantity="Position", each 
      final unit =                                                                               "m") 
    "Position vector from origin of frame_a to head of arrow, resolved in frame_a";

protected 
  Visualizers.Advanced.Arrow arrow(
    R=frame_a.R,
    r=frame_a.r_0,
    r_tail=r_tail,
    r_head=r_head,
    diameter=diameter,
    color=color,
    specularCoefficient=specularCoefficient) if world.enableAnimation and animation;
equation 
  frame_a.f = zeros(3);
  frame_a.t = zeros(3);

end SignalArrow;

Modelica.Mechanics.MultiBody.Visualizers.Ground

Information

This shape visualizes the x-y plane by a box

Parameters

Type	Name	Default	Description
Boolean	animation	true	= true, if animation of ground shall be enabled
Position	length	10	Length and width of box (center is at x=y=0) [m]
Position	height	0.02	Height of box (upper surface is at z=0, lower surface is at z=-height) [m]
Color	groundColor	{0,255,0}	Color of box

Modelica definition

model Ground "Visualize ground (box in z=0)"
   parameter Boolean animation=true 
    "= true, if animation of ground shall be enabled";
   parameter Modelica.SIunits.Position length = 10 
    "Length and width of box (center is at x=y=0)";
   parameter Modelica.SIunits.Position height = 0.02 
    "Height of box (upper surface is at z=0, lower surface is at z=-height)";
   parameter Modelica.Mechanics.MultiBody.Types.Color groundColor={0,255,0} 
    "Color of box";

   Modelica.Mechanics.MultiBody.Visualizers.FixedShape ground(
     lengthDirection={1,0,0},
     widthDirection={0,1,0},
     animation=animation,
     r_shape={-length/2,0,-height},
     length=length,
     height=height,
     color=groundColor,
     width=length);
   Modelica.Mechanics.MultiBody.Parts.Fixed fixed;
equation 

   connect(fixed.frame_b, ground.frame_a);
end Ground;