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0031635: Documentation - minor clean-up of User Guide for Foundation Classes module

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Changes in Technical Overview:
Corrected reference of "Mesh" as dedicated module, which is actually a Toolkit within "Modeling Algorithms" module.
Reduced references to "Configurable optimized memory manager",
which has not been updated for a long time and no more encouraged to be used as replacement of standard memory allocator of C library.
VRML/STL converters have been moved from section Mesh to Data Exchange.
Visualization chapter has been slightly reworded and reordered;
added references to PBR metallic-roughness material model.
Data Exchange chapter - reworded sentence "The exchanges run smoothly regardless of the quality of external data..."
to "This module handles various problems of interoperability between CAD systems...";
added AP242 to the list of STEP capabilities.

Changes in User Guide for Foundation Classes:
Removed references to "physical quantities" in package Quanity, deprecated since #0028799 and not actually used anywhere.
Adjusted description of string classes to avoid duplicated statements.
Collections section has been refactored to replace obsolete TCollection references by NCollection.
Remove obsolete statement "furthermore *catch()* statement does not allow passing exception object as argument".

Fixed broken nested enumeration in a couple of places.
Fixed usage of inappropriate quote symbols in code snippets.
Fixed references to non-existing classes like ZeroDivide instead of Standard_DivideByZero.
Removed suggested usage of Standard_Failure::Raise() instead of "throw Standard_Failure()" following #0026937.
Code snippets now suggest "catch(const Standard_Failure& )" instead of "catch(Standard_Failure )" (#0026937).
Fixed broken code snippets with lost symbols like <<.

Cosmetics: removed numerous trailing spaces, double spaces.
Added missing {.cpp} language qualifier to code quotations.
Sentences within paragraphs have been split into multiple lines in source file.
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kgv 2020-06-26 23:49:48 +03:00 committed by bugmaster
parent dad7fede39
commit 8b742dc132
2 changed files with 1275 additions and 1280 deletions
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239
dox/technical_overview/technical_overview.md
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@ -26,7 +26,7 @@ This modular structure is illustrated in the diagram below.
* @ref OCCT_TOVW_SECTION_2 "Foundation Classes" module underlies all other OCCT classes;
* @ref OCCT_TOVW_SECTION_3 "Modeling Data" module supplies data structures to represent 2D and 3D geometric primitives and their compositions into CAD models;
* @ref OCCT_TOVW_SECTION_4 "Modeling Algorithms" module contains a vast range of geometrical and topological algorithms;
* @ref OCCT_TOVW_SECTION_4a "Mesh" module implements tessellated representations of objects;
* @ref OCCT_TOVW_SECTION_4a "Mesh" toolkit from "Modeling Algorithms" module implements tessellated representations of objects;
* @ref OCCT_TOVW_SECTION_5 "Visualization" module provides complex mechanisms for graphical data representation;
* @ref OCCT_TOVW_SECTION_6 "Data Exchange" module inter-operates with popular data formats and relies on @ref OCCT_TOVW_SECTION_6a "Shape Healing" to improve compatibility between CAD software of different vendors;
* @ref OCCT_TOVW_SECTION_7 "Application Framework" module offers ready-to-use solutions for handling application-specific data (user attributes) and commonly used functionality (save/restore, undo/redo, copy/paste, tracking CAD modifications, etc).
@ -38,21 +38,20 @@ In addition, @ref OCCT_TOVW_SECTION_8 "Open CASCADE Test Harness", also called D
**Foundation Classes** module contains data structures and services used by higher-level Open CASCADE Technology classes:
* Primitive types, such as Boolean, Character, Integer or Real;
* String classes that handle ASCII and Unicode strings;
* String classes that handle Unicode strings;
* Collection classes that handle statically or dynamically sized aggregates of data, such as arrays, lists, queues, sets and hash tables (data maps).
* Classes providing commonly used numerical algorithms and basic linear algebra calculations (addition, multiplication, transposition of vectors and matrices, solving linear systems etc).
* Fundamental types representing physical quantities and supporting date and time information;
* Fundamental types like color, date and time information;
* Primitive geometry types providing implementation of basic geometric and algebraic entities that define and manipulate elementary data structures.
* Exception classes that describe situations, when the normal execution of program is abandoned;
This module also provides a variety of general-purpose services, such as:
* Safe handling of dynamically created objects, ensuring automatic deletion of unreferenced objects (smart pointers);
* Configurable optimized memory manager increasing the performance of applications that intensively use dynamically created objects;
* Standard and specialized memory allocators;
* Extended run-time type information (RTTI) mechanism maintaining a full type hierarchy and providing means to iterate over it;
* Encapsulation of C++ streams;
* Automated management of heap memory by means of specific allocators;
* Basic interpreter of expressions facilitating the creation of customized scripting tools, generic definition of expressions, etc.;
* Tools for dealing with configuration resource files and customizable message files facilitating multi-language support in applications;
* Tools for dealing with configuration resource files and customizable message files facilitating multi-language support in applications;
* Progress indication and user break interfaces, giving a possibility even for low-level algorithms to communicate with the user in a universal and convenient way;
* and many others...
@ -62,28 +61,33 @@ See also: our <a href="https://www.opencascade.com/content/tutorial-learning">E-
@section OCCT_TOVW_SECTION_3 Modeling Data
**Modeling Data** supplies data structures to implement boundary representation (BRep) of objects in 3D. In BRep the shape is represented as an aggregation of geometry within topology. The geometry is understood as a mathematical description of a shape, e.g. as curves and surfaces (simple or canonical, Bezier, NURBS, etc). The topology is a data structure binding geometrical objects together.
**Modeling Data** supplies data structures to implement boundary representation (BRep) of objects in 3D.
In BRep the shape is represented as an aggregation of geometry within topology.
The geometry is understood as a mathematical description of a shape, e.g. as curves and surfaces (simple or canonical, Bezier, NURBS, etc).
The topology is a data structure binding geometrical objects together.
Geometry types and utilities provide geometric data structures and services for:
* Description of points, vectors, curves and surfaces:
* their positioning in 3D space using axis or coordinate systems, and
* their geometric transformation, by applying translations, rotations, symmetries, scaling transformations and combinations thereof.
* their positioning in 3D space using axis or coordinate systems, and
* their geometric transformation, by applying translations, rotations, symmetries, scaling transformations and combinations thereof.
* Creation of parametric curves and surfaces by interpolation and approximation;
* Algorithms of direct construction;
* Conversion of curves and surfaces to NURBS form;
* Computation of point coordinates on 2D and 3D curves;
* Calculation of extrema between geometric objects.
Topology defines relationships between simple geometric entities. A shape, which is a basic topological entity, can be divided into components (sub-shapes):
Topology defines relationships between simple geometric entities.
A shape, which is a basic topological entity, can be divided into components (sub-shapes):
* Vertex -- a zero-dimensional shape corresponding to a point;
* Edge -- a shape corresponding to a curve and bounded by a vertex at each extremity;
* Wire -- a sequence of edges connected by their vertices;
* Face -- a part of a plane (in 2D) or a surface (in 3D) bounded by wires;
* Shell -- a collection of faces connected by edges of their wire boundaries;
* Solid -- a finite closed part of 3D space bounded by shells;
* Compound solid -- a collection of solids connected by faces of their shell boundaries.
* Composite solid -- a collection of solids connected by faces of their shell boundaries;
* Compound -- a collection of shapes of arbitrary type.
Complex shapes can be defined as assemblies of simpler entities.
Complex shapes can be defined as assemblies (compounds) of simpler entities.
See the details in @ref occt_user_guides__modeling_data "Modeling Data User's Guide"
@ -94,56 +98,56 @@ See also: our <a href="https://www.opencascade.com/content/tutorial-learning">E-
@section OCCT_TOVW_SECTION_4 Modeling Algorithms
**Modeling Algorithms** module groups a wide range of topological and geometric algorithms used in geometric modeling. Basically, there are two groups of algorithms in Open CASCADE Technology:
* High-level modeling routines used in the real design;
* Low-level mathematical support functions used as a groundwork for the modeling API;
**Modeling Algorithms** module groups a wide range of topological and geometric algorithms used in geometric modeling.
Basically, there are two groups of algorithms in Open CASCADE Technology:
* High-level modeling routines used in the real design;
* Low-level mathematical support functions used as a groundwork for the modeling API.
* Low-level geometric tools provide the algorithms, which:
* Calculate the intersection of two curves, surfaces, or a curve and a surface;
* Project points onto 2D and 3D curves, points onto surfaces and 3D curves onto surfaces;
* Construct lines and circles from constraints;
* Construct free-form curves and surfaces from constraints (interpolation, approximation, skinning, gap filling, etc);
Low-level *geometric tools* provide the algorithms, which:
* Calculate the intersection of two curves, surfaces, or a curve and a surface;
* Project points onto 2D and 3D curves, points onto surfaces and 3D curves onto surfaces;
* Construct lines and circles from constraints;
* Construct free-form curves and surfaces from constraints (interpolation, approximation, skinning, gap filling, etc).
* Low-level topological tools provide the algorithms, which:
* Tessellate shapes;
* Check correct definition of shapes;
* Determine the local and global properties of shapes (derivatives, mass-inertia properties, etc);
* Perform affine transformations;
* Find planes in which edges are located;
* Convert shapes to NURBS geometry;
* Sew connected topologies (shells and wires) from separate topological elements (faces and edges).
Low-level *topological tools* provide the algorithms, which:
* Tessellate shapes;
* Check correct definition of shapes;
* Determine the local and global properties of shapes (derivatives, mass-inertia properties, etc);
* Perform affine transformations;
* Find planes in which edges are located;
* Convert shapes to NURBS geometry;
* Sew connected topologies (shells and wires) from separate topological elements (faces and edges).
Top-level API provides the following functionality:
* Construction of Primitives:
* Boxes;
* Prisms;
* Cylinders;
* Cones;
* Spheres;
* Toruses.
* Kinematic Modeling:
* Prisms -- linear sweeps;
* Revolutions -- rotational sweeps;
* Pipes -- general-form sweeps;
* Lofting.
* Construction of Primitives:
* Boxes;
* Prisms;
* Cylinders;
* Cones;
* Spheres;
* Toruses.
* Kinematic Modeling:
* Prisms -- linear sweeps;
* Revolutions -- rotational sweeps;
* Pipes -- general-form sweeps;
* Lofting.
@figure{/technical_overview/images/0001.png "Shapes containing pipes with variable radius produced by sweeping"}
* Boolean Operations, which allow creating new shapes from the combinations of source shapes. For two shapes *S1* and *S2*:
* *Common* contains all points that are in *S1* and *S2*;
* *Fuse* contains all points that are in *S1* or *S2*;
* *Cut* contains all points in that are in *S1* and not in *S2*
* Boolean Operations, which allow creating new shapes from the combinations of source shapes. For two shapes *S1* and *S2*:
* *Common* contains all points that are in *S1* and *S2*;
* *Fuse* contains all points that are in *S1* or *S2*;
* *Cut* contains all points in that are in *S1* and not in *S2*.
See @ref occt_user_guides__boolean_operations "Boolean Operations" User's Guide for detailed documentation.
* Algorithms for local modifications such as:
* Hollowing;
* Shelling;
* Creation of tapered shapes using draft angles;
* Algorithms to make fillets and chamfers on shape edges, including those with variable radius (chord).
* Algorithms for local modifications such as:
* Hollowing;
* Shelling;
* Creation of tapered shapes using draft angles;
* Algorithms to make fillets and chamfers on shape edges, including those with variable radius (chord).
* Algorithms for creation of mechanical features, i.e. depressions, protrusions, ribs and grooves or slots along planar or revolution surfaces.
* Algorithms for creation of mechanical features, i.e. depressions, protrusions, ribs and grooves or slots along planar or revolution surfaces.
@figure{/technical_overview/images/0004.png}
@ -151,17 +155,13 @@ See the details in @ref occt_user_guides__modeling_algos "Modeling Algorithms Us
See also: our <a href="https://www.opencascade.com/content/tutorial-learning">E-learning & Training</a> offerings.
@section OCCT_TOVW_SECTION_4a Mesh
@subsection OCCT_TOVW_SECTION_4a Mesh
**Mesh** module provides the functionality to work with tessellated representations of objects in form of triangular facets. This module contains:
**Mesh** toolkit provides the functionality to work with tessellated representations of objects in form of triangular facets. This toolkit contains:
- data structures to store surface mesh data associated to shapes and basic algorithms to handle them;
- data structures and algorithms to a build triangular surface mesh from *BRep* objects (shapes);
- data structures and algorithms to build triangular surface mesh from *BRep* objects (shapes);
- tools for displaying meshes with associated pre- and post-processor data (scalars or vectors).
Open CASCADE Technology includes two mesh converters:
- VRML converter translates Open CASCADE shapes to VRML 1.0 files (Virtual Reality Modeling Language). Two representation modes are possible: shaded, which presents shapes as sets of triangles computed by the mesh algorithm, or wireframe, which presents shapes as sets of curves.
- STL converter translates Open CASCADE shapes to STL files. STL (STtereoLithography) format is widely used for rapid prototyping (3D printing).
Open CASCADE SAS also offers Advanced Mesh Products:
- <a href="https://www.opencascade.com/content/mesh-framework">Open CASCADE Mesh Framework (OMF)</a>
- <a href="https://www.opencascade.com/content/express-mesh">Express Mesh</a>
@ -170,61 +170,70 @@ Open CASCADE SAS also offers Advanced Mesh Products:
@section OCCT_TOVW_SECTION_5 Visualization
**Visualization** module provides ready-to-use algorithms to create graphic presentations from various objects: shapes, meshes, etc.
In Open CASCADE Technology visualization is based on the separation of CAD data and its graphical presentation. The presentations can be customized to take the specificity of your application into account.
**Visualization** module provides ready-to-use algorithms to create graphic presentations from various objects: shapes, meshes, etc.
In Open CASCADE Technology visualization is based on the separation of CAD data and its graphical presentation.
The module also supports a fast and powerful interactive selection mechanism.
The view facilities provided by OCCT range from low-level tools working with basic geometry and topology (such as NURBS visualization with control points and nodes, rendering of isolines to estimate speed and quality of parameterization, or rendering of a parametric profile of edges) to high-level tools for real time quality rendering of models using ray tracing: shades, reflections, transparency, anti-aliasing, etc.
Visualization module relies on the following key toolkits:
- *TKV3d* toolkit defines a high-level API called (Application Interactive Services* (AIS) for working with interactive objects.
- *TKService* toolkit defines a low-level API for managing and creating presentations from primitive arrays.
This toolkit defines an abstraction layer for defining an arbitrary graphic driver responsible for actual rendering.
- *TKOpenGl* toolkit implements the graphic driver using OpenGL and OpenGL ES libraries.
Here are just a few examples:
While low-level API operates with primitive arrays (triangles, lines, points), the higher level includes services for building presentations for B-Rep shapes (shaded and wireframe).
A comprehensive list of standard interactive objects includes topological shape, mesh presentation, various dimensions, manipulators and others.
It provides a solid basis for rapid application development, while flexible and extensible API allows development of highly customized application-specific presentations.
* Camera-driven view projection and orientation. It is possible to choose between perspective, orthographic and stereographic projection.
* Real-time ray tracing technique using recursive Whitted's algorithm and Bounded Volume Hierarchy effective optimization structure.
@figure{/technical_overview/images/0002.png, "Real time visualization by ray tracing method"}
* Support of GLSL shaders. The shader management is fully automatic, like with any other OpenGL resource.
Here are a few examples of OCCT Visualization features:
* Camera-driven view projection and orientation.
Perspective, orthographic and stereographic projections are supported.
* Support of Common (diffuse/ambient/specular) and PBR metallic-roughness material models.
* Possibility to flexibly adjust appearance of dimensions in a 3D view.
The 3D text object represents a given text string as a true 3D object in the model space.
* Definition of clipping planes through the plane equation coefficients.
Ability to define visual attributes for cross-section at the level or individual clipping planes.
In the image below different parts of the rocket are clipped with different planes and hatched.
@figure{/technical_overview/images/0008.png, "Display of shape cross-section and dimensions"}
* Support of built-in and application-specific GLSL shaders.
@figure{/technical_overview/images/0013.png, "Fragment shader implementing custom clipping surface"}
* Support of standard and custom materials, defined by transparency, diffuse, ambient and specular reflection and refraction index. The latter allows implementing transparent materials, such as glass, diamond and water.
* Optimization of rendering performance through the algorithms of:
* View frustum culling, which skips the presentation outside camera at the rendering stage;
* Back face culling, which reduces the rendered number of triangles and eliminates artifacts at shape boundaries.
* Real-time ray tracing technique using recursive Whitted's algorithm and Bounded Volume Hierarchy effective optimization structure.
@figure{/technical_overview/images/0002.png, "Real time visualization by ray tracing method"}
@figure{/technical_overview/images/0012.png, "Simulation of a glass cover"}
* Optimization of rendering performance through the algorithms of:
* View frustum culling, which skips the presentation outside camera at the rendering stage and
* Back face culling, which reduces the rendered number of triangles and eliminates artifacts at shape boundaries.
* Definition of clipping planes through the plane equation coefficients. Ability to define visual attributes for cross-section at the level or individual clipping planes. In the image below different parts of the rocket are clipped with different planes and hatched.
* Possibility to flexibly adjust appearance of dimensions in a 3D view. The 3D text object represents a given text string as a true 3D object in the model space.
@figure{/technical_overview/images/0008.png, "Display of shape cross-section and dimensions"}
For more details, see @ref occt_user_guides__visualization "Visualization User's Guide".
The visualization of OCCT topological shapes by means of VTK library provided by VIS component is described in a separate @ref occt_user_guides__vis "VTK Integration Services" User's Guide.
See also: our <a href="https://www.opencascade.com/content/tutorial-learning">E-learning & Training</a> offerings.
@section OCCT_TOVW_SECTION_6 Data Exchange
**Data Exchange** allows developing OCCT-based applications that can interact with other CAD systems by writing and reading CAD models to and from external data. The exchanges run smoothly regardless of the quality of external data or requirements to its internal representation, for example, to the data types, accepted geometric inaccuracies, etc.
**Data Exchange** allows developing OCCT-based applications that can interact with other CAD systems by writing and reading CAD models to and from external data.
@figure{/technical_overview/images/0014.png,"Shape imported from STEP"}
**Data Exchange** is organized in a modular way as a set of interfaces that comply with various CAD formats: IGES, STEP, STL, VRML, etc. The interfaces allow software based on OCCT to exchange data with various CAD/PDM software packages, maintaining a good level of interoperability.
**Data Exchange** is organized in a modular way as a set of interfaces that comply with various CAD formats: IGES, STEP, STL, VRML, etc.
The interfaces allow software based on OCCT to exchange data with various CAD/PDM software packages, maintaining a good level of interoperability.
This module handles various problems of interoperability between CAD systems, caused by differences in model validity criteria and requirements to internal representation.
* **Standardized Data Exchange** interfaces allow querying and examining the input file, converting its contents to a CAD model and running validity checks on a fully translated shape. The following formats are currently supported.
* @ref occt_user_guides__step "STEP" (AP203 : Mechanical Design, this covers General 3D CAD; AP214: Automotive Design)
* @ref occt_user_guides__iges "IGES" (up to 5.3)
* glTF, OBJ, VRML and STL meshes.
* **Standardized Data Exchange** interfaces allow querying and examining the input file, converting its contents to a CAD model and running validity checks on a fully translated shape.
The following formats are currently supported:
* @ref occt_user_guides__step "STEP" (AP203: Mechanical Design, this covers General 3D CAD; AP214: Automotive Design; AP242).
* @ref occt_user_guides__iges "IGES" (up to 5.3).
* **glTF** 2.0 reader and writer.
* **OBJ** mesh file reader.
* **VRML** converter translates Open CASCADE shapes to VRML 1.0 files (Virtual Reality Modeling Language).
* **STL** converter translates Open CASCADE shapes to STL files.
STL (STtereoLithography) format is widely used for rapid prototyping (3D printing).
* @ref occt_user_guides__xde "Extended data exchange" (XDE) allows translating additional attributes attached to geometric data (colors, layers, names, materials etc).
* <a href="https://www.opencascade.com/content/advanced-data-exchange-components">Advanced Data Exchange Components</a> are available in addition to standard Data Exchange interfaces to support interoperability and data adaptation (also using @ref OCCT_TOVW_SECTION_6a "Shape Healing") with CAD software using the following proprietary formats:
* <a href="https://www.opencascade.com/content/advanced-data-exchange-components">Advanced Data Exchange Components</a>
are available in addition to standard Data Exchange interfaces to support interoperability and data adaptation (also using @ref OCCT_TOVW_SECTION_6a "Shape Healing") with CAD software using the following proprietary formats:
* <a href="https://www.opencascade.com/content/acis-sat-import-export">ACIS SAT</a>
* <a href="https://www.opencascade.com/content/parasolid-import">Parasolid</a>
* <a href="https://www.opencascade.com/content/dxf-import-export">DXF</a>
@ -238,22 +247,22 @@ These components are based on the same architecture as interfaces with STEP and
**Shape Healing** library provides algorithms to correct and adapt the geometry and topology of shapes imported to OCCT from other CAD systems.
Shape Healing algorithms include, but are not limited to, the following operations:
* analyze shape characteristics and, in particular, identify the shapes that do not comply with OCCT geometry and topology validity rules by analyzing geometrical objects and topology:
- check edge and wire consistency;
- check edge order in a wire;
- check the orientation of face boundaries;
- analyze shape tolerances;
- identify closed and open wires in a boundary.
* fix incorrect or incomplete shapes:
- provide consistency between a 3D curve and its corresponding parametric curve;
- repair defective wires;
- fit the shapes to a user-defined tolerance value;
- fill gaps between patches and edges.
* upgrade and change shape characteristics:
- reduce curve and surface degree;
- split shapes to obtain C1 continuity;
- convert any types of curves or surfaces to Bezier or B-Spline curves or surfaces and back;
- split closed surfaces and revolution surfaces.
* Analyze shape characteristics and, in particular, identify the shapes that do not comply with OCCT geometry and topology validity rules by analyzing geometrical objects and topology:
- check edge and wire consistency;
- check edge order in a wire;
- check the orientation of face boundaries;
- analyze shape tolerances;
- identify closed and open wires in a boundary.
* Fix incorrect or incomplete shapes:
- provide consistency between a 3D curve and its corresponding parametric curve;
- repair defective wires;
- fit the shapes to a user-defined tolerance value;
- fill gaps between patches and edges.
* Upgrade and change shape characteristics:
- reduce curve and surface degree;
- split shapes to obtain C1 continuity;
- convert any types of curves or surfaces to Bezier or B-Spline curves or surfaces and back;
- split closed surfaces and revolution surfaces.
Each sub-domain of Shape Healing has its own scope of functionality:
@ -269,21 +278,24 @@ For more details, refer to @ref occt_user_guides__shape_healing "Shape Healing U
See also: our <a href="https://www.opencascade.com/content/tutorial-learning">E-learning & Training</a> offerings.
@section OCCT_TOVW_SECTION_7 Application Framework
**Open CASCADE Application Framework** (OCAF) handles Application Data basing on the Application/Document paradigm. It uses an associativity engine to simplify the development of a CAD application thanks to the following ready-to-use features and services:
**Open CASCADE Application Framework** (OCAF) handles Application Data basing on the Application/Document paradigm.
It uses an associativity engine to simplify the development of a CAD application thanks to the following ready-to-use features and services:
* Data attributes managing the application data, which can be organized according to the development needs;
* Data storage and persistence (open/save);
* Possibility to modify and recompute attributes in documents. With OCAF it is easy to represent the history of modification and parametric dependencies within your model;
* Possibility to modify and recompute attributes in documents.
With OCAF it is easy to represent the history of modification and parametric dependencies within your model;
* Possibility to manage multiple documents;
* Predefined attributes common to CAD/CAM/CAE applications (e.g. to store dimensions);
* Undo-Redo and Copy-Paste functions.
Since OCAF handles the application structure, the only development task is the creation of application-specific data and GUIs.
OCAF differs from any other CAD framework in the organization of application data, as there the data structures are based on reference keys rather than on shapes. In a model, such attributes as shape data, color and material are attached to an invariant structure, which is deeper than the shapes. A shape object becomes the value of *Shape* attribute, in the same way as an integer number is the value of *Integer* attribute and a string is the value of *Name* attribute.
OCAF differs from any other CAD framework in the organization of application data, as there the data structures are based on reference keys rather than on shapes.
In a model, such attributes as shape data, color and material are attached to an invariant structure, which is deeper than the shapes.
A shape object becomes the value of *Shape* attribute, in the same way as an integer number is the value of *Integer* attribute and a string is the value of *Name* attribute.
OCAF organizes and embeds these attributes in a document. OCAF documents, in their turn, are managed by an OCAF application.
@ -291,10 +303,11 @@ For more details, see @ref occt_user_guides__ocaf "OCAF User's Guide".
See also: our <a href="https://www.opencascade.com/content/tutorial-learning">E-learning & Training</a> offerings.
@section OCCT_TOVW_SECTION_8 Draw Test Harness
**Test Harness** or **Draw** is a convenient testing tool for OCCT libraries. It can be used to test and prototype various algorithms before building an entire application. It includes:
**Test Harness** or **Draw** is a convenient testing tool for OCCT libraries.
It can be used to test and prototype various algorithms before building an entire application.
It includes:
- A command interpreter based on the TCL language;
- A number of 2D and 3D viewers;
- A set of predefined commands.

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