# Documentation

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# Solid

Solid element with geometry, inertia, and color

• Library:
• Body Elements

## Description

The Solid block adds a solid element with geometry, inertia, and color to the attached frame. The solid element can be a simple rigid body or part of a compound rigid body—a group of rigidly connected solids, often separated in space through rigid transformations. Combine Solid and Rigid Transform blocks to model a compound rigid body.

Geometry parameters include shape and size. You can choose from a list of preset shapes or import a custom shape from an external file in STL or STEP format. By default, for all but STL-derived shapes, the block automatically computes the solid inertia from the specified geometry and mass or mass density. You can change this setting in the Inertia > Type block parameter.

A reference frame encodes the position and orientation of the solid. In the default configuration, the block provides only the reference frame. A frame-creation interface provides the means to define additional frames based on solid geometry features. You access this interface by selecting the Create button in the Frames expandable area.

The block dialog box contains a collapsible visualization pane. This pane provides instant visual feedback on the solid you are modeling. Use it to find and fix any issues with the shape and color of the solid. You can examine the solid from different perspectives by selecting a standard view or by rotating, panning, and zooming the solid.

### Visualization Pane

Select the Update Visualization button to view the latest changes to the solid geometry in the visualization pane. Select Apply or OK to commit your changes to the solid. Closing the block dialog box without first selecting Apply or OK causes the block to discard those changes.

Solid Visualization Pane

Right-click the visualization pane to access the visualization context-sensitive menu. This menu provides additional options so that you can change the background color, split the visualization pane into multiple tiles, and modify the view convention from the default +Z up (XY Top) setting.

### C/C++ Code Generation

This block supports code generation for real-time simulation tasks. Certain blocks and block settings may be more suitable for simulation on a real-time device. For suggestions on how to improve real-time simulation performance, use the Simulink® Performance Advisor (Simulink). Suggestions include ways to reduce model complexity where helpful and to decrease numerical stiffness.

Select Analysis > Performance Tools > Performance Advisor in the Simulink menu bar to open the Performance Advisor. Set the Activity parameter to `Execute real-time application` to view suggestions specific to real-time simulation performance. Expand the Real-Time node in the tree view pane to select performance checks specific to Simscape™ products.

## Ports

### Frame

expand all

Local reference frame of the solid element. Connect to a frame line or frame port to define the relative position and orientation of the solid.

## Parameters

expand all

#### Geometry

Geometrical shape of the solid element:

• `Cylinder` — Cylindrical shape with geometry center coincident with the reference frame origin and symmetry axis coincident with the reference frame z axis.

• `Sphere` — Spherical shape with geometry center coincident with the reference frame origin.

• `Brick` — Prismatic shape with geometry center coincident with the reference frame origin and prismatic surfaces normal to the reference frame x, y, and z axes.

• `Ellipsoid` — Three-dimensional extension of the ellipse with geometry center coincident with the reference frame origin and semi-principal axes coincident with the reference frame x, y, and z axes.

• `Regular Extrusion` — Translational sweep of a regular polygon cross section with geometry center coincident with the reference frame origin and extrusion axis coincident with the reference frame z axis.

• `General Extrusion` — Translational sweep of a general cross section with geometry center coincident with the [0 0] coordinate on the cross-sectional XY plane and extrusion axis coincident with the reference frame z axis.

• `Revolution` — Rotational sweep of a general cross section with geometry center coincident with the [0 0] coordinate on the cross-sectional XZ plane and revolution axis coincident with the reference frame z axis.

• `From File` — Imported custom shape with geometry center and orientation as defined in STL or STEP geometry file.

Distance R in the figure, specified as a scalar in terms of the selected physical units.

Distance L in the figure, specified as a scalar in terms of the selected physical units.

Distance R in the figure, specified as a scalar in terms of the selected physical units.

Dimensions x, y, and z in the figure, specified in this order as a three-element vector in terms of the selected physical units.

Dimensions x, y, and z in the figure, specified in this order as a three-element vector in terms of the selected physical units. The ellipsoid reduces to a sphere when all three radii have the same have.

Edge count of the polygon cross section, specified as a scalar number greater than `2`. The default value of `3` corresponds to a triangle, the polygon with the lowest possible number of sides. The figure shows a regular extrusion with a pentagon for cross section.

Distance R in the figure, specified as a scalar in terms of the selected physical units. The enveloping circle highlights the relationship between the outer circle radius and the polygon center-to-vertex distance.

Distance L in the figure, specified as a scalar in terms of the selected physical units.

Cross-sectional shape specified as an [x,y] coordinate matrix, with each row corresponding to a point on the cross-sectional profile. The coordinates specified must define a closed loop with no self-intersecting segments.

The coordinates must be arranged such that from one point to the next the solid region always lies to the left. The block extrudes the cross-sectional shape specified along the z axis to obtain the extruded solid.

Distance to sweep the extrusion cross section by. The block extrudes the cross section by half the extrusion length along the +z axis and by half along the -z axis.

Cross-sectional shape specified as an [x,z] coordinate matrix, with each row corresponding to a point on the cross-sectional profile. The coordinates specified must define a closed loop with no self-intersecting segments.

The coordinates must be arranged such that from one point to the next the solid region always lies to the left. The block revolves the cross-sectional shape specified about the reference frame z axis to obtain the revolved solid.

Type of revolution sweep to use. Use the default setting of `Full` to revolve the cross-sectional shape by the maximum 360 degrees. Select `Custom` to revolve the cross-sectional shape by a lesser angle.

Angle to sweep a partial revolution cross section by. The block revolves the specified cross section by half the revolution angle in the clockwise direction and by half in the counterclockwise direction.

Geometry file type to import. The block provides automatic inertia calculation from geometry for STEP files only. For STL geometry files, you must manually enter the solid inertia using the `Custom` or ```Point Mass``` parameterization.

Geometry file name, complete with path and extension—e.g., ‘C:/Users/Jdoe/Documents/myShape.STEP'

Unit of length for STL file coordinates.

#### Inertia

Inertia parameterization to use. Select `Point Mass` to model a concentrated mass with negligible rotational inertia. Select `Custom` to model a distributed mass with the specified moments and products of inertia. The default setting, `Calculate from Geometry`, enables the block to automatically calculate the rotational inertia properties from the solid geometry and specified mass or mass density.

Parameter to use in inertia calculation. The block obtains the inertia tensor from the solid geometry and the parameter selected. Use `Density` if the material properties are known. Use `Mass` if the total solid mass if known.

Mass per unit volume of material. The mass density can take on a positive or negative value. Specify a negative mass density to model the effects of a void or cavity in a solid body.

Aggregate mass of the solid. The mass can be a positive or negative value. Specify a negative mass to model the aggregate effect of voids and cavities in a compound body.

[x y z] coordinates of the center of mass relative to the block reference frame. The center of mass coincides with the center of gravity in uniform gravitational fields only.

Three-element vector with the [Ixx Iyy Izz] moments of inertia specified relative to a frame with origin at the center of mass and axes parallel to the block reference frame. The moments of inertia are the diagonal elements of the inertia tensor

`$\left(\begin{array}{ccc}{I}_{xx}& & \\ & {I}_{yy}& \\ & & {I}_{zz}\end{array}\right),$`

where:

• ${I}_{xx}=\underset{V}{\int }\left({y}^{2}+{z}^{2}\right)\text{\hspace{0.17em}}dm$

• ${I}_{yy}=\underset{V}{\int }\left({x}^{2}+{z}^{2}\right)\text{\hspace{0.17em}}dm$

• ${I}_{zz}=\underset{V}{\int }\left({x}^{2}+{y}^{2}\right)\text{\hspace{0.17em}}dm$

Three-element vector with the [Iyz Izx Ixy] products of inertia specified relative to a frame with origin at the center of mass and axes parallel to the block reference frame. The products of inertia are the off-diagonal elements of the inertia tensor

`$\left(\begin{array}{ccc}& {I}_{xy}& {I}_{zx}\\ {I}_{xy}& & {I}_{yz}\\ {I}_{zx}& {I}_{yz}& \end{array}\right),$`

where:

• ${I}_{yz}=-\underset{V}{\int }yz\text{\hspace{0.17em}}dm$

• ${I}_{zx}=-\underset{V}{\int }zx\text{\hspace{0.17em}}dm$

• ${I}_{xy}=-\underset{V}{\int }xy\text{\hspace{0.17em}}dm$

#### Graphic

Visualization setting for this solid. Use the default setting, ```From Geometry```, to show the solid geometry. Select `Marker` to show a graphic marker such as a sphere or frame. Select `None` to disable visualization for this solid.

Geometrical shape of the graphic marker. Mechanics Explorer shows the marker using the selected shape.

Absolute size of the graphic marker in screen pixels. The marker size is invariant with zoom level.

Parameterization for specifying visual properties. Select `Simple` to specify color and opacity. Select `Advanced` to add specular highlights, ambient shadows, and self-illumination effects.

RGB color vector with red (R), green (G), and blue (B) color amounts specified on a 0–1 scale. A color picker provides an alternative interactive means of specifying a color. If you change the Visual Properties setting to `Advanced`, the color specified in this parameter becomes the Diffuse Color vector.

Graphic opacity specified on a scale of 0–1. An opacity of `0` corresponds to a completely transparent graphic and an opacity of `1` to a completely opaque graphic.

True color under direct white light specified as an [R,G,B] or [R,G,B,A] vector on a 0–1 scale. An optional fourth element specifies the color opacity also on a scale of 0–1. Omitting the opacity element is equivalent to specifying a value of `1`.

Color of specular highlights specified as an [R,G,B] or [R,G,B,A] vector on a 0–1 scale. The optional fourth element specifies the color opacity. Omitting the opacity element is equivalent to specifying a value of `1`.

Color of shadow areas in diffuse ambient light, specified as an [R,G,B] or [R,G,B,A] vector on a 0–1 scale. The optional fourth element specifies the color opacity. Omitting the opacity element is equivalent to specifying a value of `1`.

Surface color due to self illumination, specified as an [R,G,B] or [R,G,B,A] vector on a 0–1 scale. The optional fourth element specifies the color opacity. Omitting the opacity element is equivalent to specifying a value of `1`.

Sharpness of specular light reflections, specified as a scalar number on a 0–128 scale. Increase the shininess value for smaller but sharper highlights. Decrease the value for larger but smoother highlights.

#### Frames

Clear the check box to hide the reference frame port in the Solid block. Hiding the reference frame port suppresses the frame visualization in Mechanics Explorer. You must expose the reference frame port if the block has no custom frames.

Select the Create button to define a new frame using the frame-creation interface. Each new frame appears on a row above the New Frame parameter. To edit an existing frame, select the Edit button . To delete an existing frame, select the Delete button .

#### Frame Creation Interface

Frame identifier specified as a MATLAB string. This string identifies the frame port in the block diagram and in the tree view pane of Mechanics Explorer. Keep the frame name short to ensure it fits in the block icon width.

Select the location of the frame origin. Options include:

• At Reference Frame Origin — Make the new frame origin coincident with the reference frame origin. This is the default option.

• At Center of Mass — Make the new frame origin coincident with the solid center of mass. The reference frame origin is located at the center of mass in symmetrical shapes such as spheres and bricks but not in certain extrusions or revolutions.

• Based on Geometric Feature — Place the new frame origin at the center of the selected geometry feature. Valid geometry features include surfaces, lines, and points. You must select a geometry feature from the visualization pane and then select the Use Selected Feature button. The name of the selected geometry feature appears in the field below this option.

Select the axis of the new frame that you want to set as the primary axis. The primary axis constrains the possible orientations of the remaining two axes. Specify the orientation of the primary axis by selecting from the following options:

• Along Reference Frame Axis — Align the primary axis with the selected axis of the reference frame.

• Along Principal Inertia Axis — Align the primary axis with the selected principal inertia axis. The principal inertia axes are those about which the products of inertia are zero.

• Based on Geometric Feature — Align the primary axis with the vector associated with the selected geometric feature. Valid geometric features include surfaces and lines.

Select the axis of the new frame that you want to set as the secondary axis. The secondary axis is the projection of the selected direction onto the normal plane of the primary axis. Select the direction to project from the following options:

• Along Reference Frame Axis — Project the selected reference frame axis onto the normal plane of the primary axis. Align the secondary axis with the projection.

• Along Principal Inertia Axis — Project the selected principal inertia axis onto the normal plane of the primary axis. Align the secondary axis with the projection. The principal inertia axes are those about which the products of inertia are zero.

• Based on Geometric Feature — Project the vector associated with the selected geometry feature onto the normal plane of the primary axis. Align the secondary axis with the projection. Valid geometry features include surfaces and lines. You must select a geometry feature from the visualization pane and then select the Use Selected Feature button.

## See Also

### Topics

#### Introduced in R2012a

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