User’s Guide – Lite Edition

Terra Power Tools – Lite Edition
User’s Guide


Terra Power Tools (Lite Edition) extends the core functionality of AutoCAD® Civil3D® by providing a comprehensive set of surface creation and extensive volumetric analysis tools. The created surfaces and results of the analyses can be exported as tabular text, or geometric data back to AutoCAD Civil 3D, and also saved to the Windows clipboard as CSV data. Material ‘mesh’ data data exported to AutoCAD Civil 3D can be further analyzed and documented using Visual Report Designer.


Additional features are available in Terra Power Tools – Professional Edition, including solid model visualization, support for multiple drawings/data sources, cross and profile section generation, etc.

User Interface

Although Terra Power Tools runs in its own UI separate from AutoCAD Civil 3D, it functions as just another AutoCAD Civil 3D dialog that operates on certain AutoCAD Civil 3D objects to perform some analyses. In this sense, an instance of Terra Power Tools is tightly associated with its active drawing – all analyses, import and export activity is restricted to that one drawing. If at any time the associated drawing is switched in AutoCAD Civil 3D, Terra Power Tools enters a suspended state where all commands are disabled. Switching back to the associated drawing restores the active state. While tightly integrated with AutoCAD Civil 3D, the Terra Power Tools UI is built to allow both applications to remain responsive even if the other is ‘busy’ processing a command. Also, objects and analysis results created in Terra Power Tools are not automatically inserted into AutoCAD Civil 3D, thus allowing for ad-hoc calculations that do not clutter your active drawing with extraneous data or objects.


The following is a summary of the commands available in Terra Power Tools:

  • Create/Modify Surfaces

New surface entities can be created from existing ones by performing any of several geometric operations:

    • Topmost / Bottommost: Selected surfaces are combined such that the elevation of the resulting surface at any point is either the highest or the lowest of all the combined surfaces.
    • Split: A given surface, A, is used to split another surface, B, resulting in (possibly) three other surfaces representing the regions of B that are above, below, or outside of surface A.
    • Clip: A boundary entity, B, is used to clip a surface, A, producing a smaller surface representing the region of A that is either inside or outside the clip boundary B.
    • Vertical Offset: A given surface, A, is used to create a set of one or more surfaces, {Bi}, such that the elevation at any point of surface Bi is the elevation of surface A at that point plus/minus a provided offset value.
    • Level: Same-elevation surfaces are created at one or more specified values.
  • Analyze – Create Material Meshes

Very powerful, comprehensive volumetric analyses between surfaces can be carried out using a Material Table, which allows identification/designation of volumetric regions bounded by different surfaces as Materials. Using simple rules, these materials are defined as volumetric envelopes that are bounded Above, Below, Immediately Above, or Immediately Below by a set of surfaces. Volumes and 2D areas are reported for each material in tabular form and as a chart. Additionally, the individual materials can be viewed in AutoCAD Civil 3D as meshes.

Main Window Components

The main user interface elements of Terra Power Tools are shown below:

  1. The Ribbon Panel hosts command buttons separated into groups:
    1. The Material Sets group allows creation of a new Material Set each of which contains one or more material definitions. The definitions can optionally be saved to the associated drawing.
    2. The Create Surfaces group has commands that allow creation of new surface entities.
    3. The Support group has commands that provide links to the help document and support pages.
  2. An Explorer Panel lists objects created and used during a typical session. It can be floated (detached from the application frame), or unpinned (hidden in the frame) as desired.
  3. A Material Set Editor Panel allows material definitions to be specified and provides a command to compute volumes according to the definitions. Results of the computation are displayed as a chart and also in tabular form.
  4. The Associated Document indicator specifies the full path name of the associated drawing.

The Explorer Panel


The Explorer Panel organizes items in a tree structure, much like the Microsoft Windows Explorer, and has a similar user interaction. Right clicking an item brings up a context menu with commands relevant to the item. Multiple items can be selected by holding down the Ctrl or Shift buttons and clicking on individual items, and also by clicking and dragging in the Item Selection panel. Clicking anywhere inside an item row makes the item active or current. Note that item selection and activation are related, but distinct, concepts – item selection allows certain commands to be applied to a set of items, whereas activating an item allows viewing or modification of its properties.

Ribbon Bars

Materials Sets Commands


Material definitions in Terra Power Tools are organized by sets, where each set represents a user-defined logical grouping of materials, such as “EG-Final Cut-Fill”, “Pond Volumes by Elevation”, or “Corridor 5c Materials”, etc. Materials belonging to a set are computed and reported together. Materials sets are also allowed to be saved to the active drawing for later retrieval.


New Materials Set

The New Materials Set command creates a new materials set, adds it to the Explorer Panel, and displays its associated editor panel, which is used to define and modify the material definitions. Note that the initial name assigned to the set can be changed in the explorer panel simply by clicking on the name and entering any sequence of characters.

Save Current Materials Set

The Save Current Materials Set command saves the existing state of the currently active materials set to the associated drawing. When a Terra Power Tools session is closed and reopened, the saved materials sets are listed in the Explorer Panel, but are not restored until specifically loaded. The right-click context menu in the Explorer Panel can be used to load, save or remove materials sets. Note that the volumes for a materials-set are computed afresh when it is loaded, and hence state its state is indicated as ‘modified’.

Save All Materials Sets

The Save All Materials Sets command saves any modified material sets to the associated drawing. Note that both Save and Save All commands are disabled if no materials sets have been modified.

Create Surfaces Commands

Commands in this group allow creation of new surfaces from existing ones by using various operations on the existing surfaces. Each command brings up a modal interface which allows setting of required/optional parameters. Clicking on the ‘OK’ button executes the command, creating one or more surfaces following the intended operation of the command. The name(s) of the created surface(s) are initially chosen to reflect the command used to create them, for example, “TOP_Surf1_Surf2” for the topmost surface of “Surf1” and “Surf2”, and can later be changed through the Explorer Panel.

Create Level Surfaces

The Create Level Surfaces command creates same-elevation surfaces at even intervals within a range of elevations, and/or at specific elevations:


The created level-surfaces’ 2D-extents are set to the maximum bounds of all surfaces available in the drawing, but can optionally be restricted to lie within any (possibly irregular) polygon. The polygonal boundary is specified by choosing from previously specified boundaries or by selecting a (closed) polyline from the drawing by clicking on the Pick button (note that the Pick button appears only when the edit field is clicked):


In general, the ‘pick’ operation allows selecting appropriate objects from the active drawing. In this mode, Terra Power Tools is first minimized, and then AutoCAD is brought to the foreground to allow for selection of items, and finally Terra Power Tools is restored to its original state.

If a picked AutoCAD Civil 3D/AutoCAD entity does not have a name, Terra Power Tools assigns one, so as to have some reference to the entity.

Create Vertical-Offset Surfaces

The Create Vertical-Offset Surfaces command creates surfaces at one or more specified vertical-offset values from a given surface, such that elevation at any point on the offset surface is equal to the elevation of the target surface at that point +/- the offset distance:


Create Split Surfaces

The Create Split Surfaces command uses a splitting surface to create sub-regions of the target surface that are above, below, or outside (the 2D bounds of) the splitting surface:


Create Clipped Surface

The Create Clipped Surface command creates a new surface that represents the resultant surface after removing a region of a given surface that lies inside or outside a specified boundary entity:


Create Topmost Surface & Create Bottommost Surface

The Create Topmost Surface command combines selected surfaces such that the elevation of the resulting surface at any point is the highest of all the combined surfaces.

Similarly, the Create Bottommost Surface command produces a surface that has the lowest elevation of the combined surfaces:


Materials Set Editor


The Materials Set Editor UI consists of four panes:

  • The Settings and Actions pane allows setting up the volume computation. The surfaces selected in the Selected Surface(s) drop down are only used for creating an initial (default) set of material definitions (also called a material table). The radio buttons in the Volume Computation group allow selection of one of two modes of computation:
    • Unbounded – volumes are computed for the entirety of all surfaces involved.
    • Bounded – volume computation is restricted within the chosen 2D Boundary.

Once the material table has valid entries, the Compute button becomes enabled and can be clicked to initiate volume computations.

  • The Material Definition pane consists of rows of material specifications that form the basis of the volume computations. The buttons at the top of the pane invoke commands that allow modifications to the material table:
    • The Create Table command creates new material definitions (or replaces existing ones) by forming materials using pairs of surfaces from the list of Selected Surfaces in the Settings and Actions pane. These definitions can be interpreted as cut-fill materials between surface pairs.
    • The Add Selected Surfaces command is used to add surfaces specified in the Settings and Actions pane as columns to the material table. In addition, a column header context menu allows adding and removing surface-columns.
    • The Add Row command adds a blank row with default comparison and material names/colors.
    • The Remove Rows command removes selected rows from the table.
    • Save and Load commands allow saving and restoring the current state of the material table to/from a text file.
    • The Validate command flags invalid material definitions, if any.
    • The Clear Table command removes all definitions from the table.
  • The Chart and Results panes are output panes only, in that, no user input is needed or allowed, except that the Results pane permits a right click export option to save the tabular results in a CSV format to the clipboard, or inserted to the active drawing.


Computing Material Volumes

Terra Power Tools provides a general-purpose method of volume computation using TIN surfaces. The method allows definition of material envelopes based on their topological relationships to bounding surfaces. For example, in the illustration below, where some surfaces are shown in a profile-section view, the green material is identified as being bounded by surfaces A, B, C, and D, with the specified relationships.


Material Tables

When TIN models are used for representing surfaces, a surprisingly small set of topological relations can be used to build very powerful material models. For Terra Power Tools, four such topological relationships are defined: Above, Below, Immediately Above, and, Immediately Below. Like in the example above, material definitions are constructed by specifying a set of surfaces along with their relationship to the material envelope.

Given a set of surfaces and a set of material definitions, Terra Power Tools first subdivides the 3D space occupied by the surfaces into polyhedrons bounded by two or more of the given surfaces. The material represented by the individual polyhedral envelopes is then determined by matching their bounding surfaces against the set of material definitions. Using the above example, the 2D equivalent of the process can be described as follows:

  1. Form all polygonal-envelopes (like the green shaded regions in the example) by intersecting line-segments representing the individual surfaces.
  2. Match the envelopes to the material definitions. In the example, only the green-shaded regions match the single definition provided, and thus will be classified as material “green”.
  3. Add areas for all envelopes for the same material to produce a composite material “area”.

A Material Table in Terra Power Tools consists of one or more rows of material definitions, each of which contains relationship-specifiers. For a set of m materials and n surfaces, the material definition consists of a table of m rows and n columns with each cell, Cij, specifying the topological relationship between the material (envelope) Mi and surface Sj:

Relationship Meaning
Above A vertical line through the material envelope will intersect the surface somewhere above it
Immediately Above The surface bounds the material envelope at the top
Below A vertical line through the material envelope will intersect the surface somewhere below it
Immediately Below The surface bounds the material envelope at the bottom
<Empty> Does not matter where the surface is in relation to the material envelope

Note that the materials Mi don’t need to be unique. In other words, multiple rows (definitions) could identify the same material, in which case the volumes (and planar areas) of all polyhedral-envelopes satisfying any of the multiple material definitions are combined. For example, in the scenario below, where all material inside the “V” shape and below the surface S3 needs to be considered as material M1, we would need to tag both the material definition rows with the same material, M1:


Some points should be noted regarding the matching of computed polyhedral-envelopes with material definitions:

  • The conditions implied by the relationship-specifiers (Above, Below, etc.) in a given row are treated as “AND” conditions. In other words, all of them have to be satisfied. Thus, for the first row in the above example, any envelope that meets the criterion of being <Above, S1> AND <Below, S3> will be classified as material M1.
  • An empty cell in the material table implies that the surface in that cell’s column will not be used when matching the material for the cell’s row. In other words, it does not matter how the surface is topologically related to the envelope, as far as the criterion in that row is concerned.
  • The ordering of the rows and columns is irrelevant.
  • The volume (and planar-area) of a computed polyhedral envelope is added to all material accumulations whose material definition it matches. Thus, it is possible that the sum of all reported material volumes exceeds the combined volumes of all polyhedrons. At this time, the only way to check for this is visually – by turning on or off the display of individual materials.


The following example illustrates the above concepts for a scenario where multiple removed material quantities are needed for a pipe or cable inserted under a trench:


First of all, we see that four different material quantities are needed, involving all the surfaces shown, except Water. Next, since only the material inside the drilling channel is of interest here, we can easily determine that all material definitions will have the following relationships:

Mi (Above, DrillChannel Bot) (Below, DrillChannel Top)

Further, since material M1 exists between the surfaces Ground and Level 1 only, it can now be completed as below. Note that the relationships specified are necessary and sufficient:

M1 (Above, DrillChannel Bot) (Below, DrillChannel Top) (Below, Ground) (Above, Level 1)

Following a similar logic for the remaining materials we get the following material table:






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