FreeCAD模块开发者指南 - CSDN文库

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"FreeCAD模组开发者指南，20160929版，英文文档，用于FreeCAD 0.17-dev版本的开发。作者Qingfeng Xia，旨在帮助新模块开发者熟悉FreeCAD的工作台GUI和API。" FreeCAD是一款开源的参数化建模软件，适用于机械工程、产品设计、3D建模等领域。该资源是《FreeCAD模块开发者指南》，主要面向希望为FreeCAD开发新模块的程序员。这个指南由Qingfeng Xia编写，针对FreeCAD的0.17-dev版本，它提供了一个深入学习FreeCAD源代码的途径。指南的早期版本始于2015年9月，当时适配的是FreeCAD 0.16-dev版本，而2016年9月更新至0.17-dev版本，这意味着内容已经跟进了软件的最新进展。文档的授权遵循与FreeCAD相同的Creative Commons Attribution 3.0许可证，允许自由分享和改编，但需给予原作者署名。在开始阅读此指南前，建议读者已经对FreeCAD的工作台界面和Python API有一定的了解，这可以通过官方wiki的基础文档和Python API文档来实现。此外，为了快速上手，还推荐使用FreeCAD的单文件PDF用户手册。文档还提到了Doxygen生成的源代码在线文档，这是对0.16-dev版本的源代码进行详细了解的重要资源。Doxygen是一个强大的源代码文档工具，能自动生成源代码的结构化文档。作者写作此书的初衷包括学习FreeCAD的软件架构，以及掌握如何使用Git为类似FreeCAD的开源项目贡献代码。这不仅有助于节省新开发者的学习时间，也鼓励更多的人参与到开源社区中来。通过这份指南，开发者将能够学习如何扩展FreeCAD的功能，创建自定义工作台，编写模块，以及理解FreeCAD的核心组件和交互机制。这将极大地提升FreeCAD的可定制性和适应性，满足不同用户和行业的特定需求。

2.3. LIST OF MODULES IN FREECAD MOD FOLDER 13

2.3 List of modules in FreeCAD Mod folder

Mechanical Engineering, CAD and CAM

• Part make primitive 3D objects like cube, cylinder, boolean operaton

The Part module is based on the professional CAD kernel , OpenCasCade, objects and functions.

• OpenSCAD Extra OpenCasCade functions

use the high level API in Part module instead

• PartDesign modelling complex solid part from 2D sketch

The Part Design Workbench provides tools for modelling complex solid parts and is based on a Feature editing

methodology to produce a single contiguous solid. It is intricately linked with the Sketcher Workbench.

• Draft draw and modify 2D objects, traditional 2D engineering drawing,

The Draft workbench allows to quickly draw simple 2D objects in the current document, and oﬀers several tools to

modify them afterwards. Some of these tools also work on all other FreeCAD objects, not only those created with

the Draft workbench. It also provides a complete snapping system, and several utilities to manage objects and

settings.

• Drawing put 3D model to paper, can save to DXF and SVG format

• Sketcher buld up 3D part from 2D sketch used in PartDesign

• Assembly Assembly of part

Constraint of

• Cam Computer aided machining (CAM), CNC machining

• Path Tool path for CAM

Civil Engineering

• Idf used by Arch module

• Arch CAD for civil engineering, like desing of a house

The Arch workbench provides modern BIM workﬂow to FreeCAD, with support for features like IFC support, fully

parametric architectural entities such as walls, structural elements or windows, and rich 2D document production.

The Arch workbench also feature all the tools from the Draft Workbench

• Ship Build 3D model (hull)for ship

Computer aided engineering (CAE)

• Points points cloud from 3D scanning

• ReverseEngineering build 3D part from points cloud

• Raytracing to render lighting 3D model more vivid as in physical world

generate photorealistic images of your models by rendering them with an external renderer. The Raytracing

workbench works with templates, the same way as the Drawing workbench, by allowing you to create a Raytracing

project in which you add views of your objects. The project can then be exported to a ready-to-render ﬁle, or be

rendered directly.

• MeshPart

• Mesh convert part into triangle mesh for rendering (tessellation)

• Fem Fenite element analysis for part design

• Robot Robot simulator

Utilities

• Plot 2D plot,like XYplot, based on matplotlib

allows to edit and save output plots created from other modules and tools

• Image import various image format, draw them in 3D plane

• Spreadsheet Excel like data view widget

Testing facility

14 CHAPTER 2. ORGANISATION OF FREECAD SOURCE CODE

• Inspection Testing

• Test Workbench for self testing

• Sandbox Testing

Meta workbench

• Web web view of FreeCAD

• Start start page of FreeCAD

• Complete show all toolbar from loadable modules

Module not visible to workbench users

• Import

• JtReader

• Material deﬁne standard material property, like density, elastic modulus

not visible to workbench users, used by Fem module

• TemplatePyMod a collection of python example DocumentObject, ViewProvider

2.4 Learning path

1. be familar with FreeCAD Gui Operation as a user

see FreeCAD wiki user hub, tutorials on youtube and user manual

2. be familar with Python scripting, learning from macro recording.

The amazing feature of FreeCAD is that all GUI operation is recorded in Python console FreeCAD wiki power user hub

FreeCAD wiki developer hub

3. be familar with key classes in FreeCAD source code: Base, App, Gui, Part

It is really challenging to code in C++, Python GIL, Coin3D, OCC. However, it is not needed to know about OCC

as module developers. FreeCAD has a online API document for import classes like Properties, Document Objects, see

http://www.freecadweb.org/wiki/index.php?title=Power_users_hub#API_Functions

4. develop/extend pure Python module, the challenging Python wrapping task can be avoided

5. develop/extend hybrid C++ and Python module

6. write 3D rendering code, i.e. ViewProvider derived classes

2.5 Learning OpenInventor/Coin3D

Usful links to learn OpenInventor programming: http://webee.technion.ac.il/~cgcourse/InventorMentor/The%20Inventor%

20Mentor.pdf Coin3D Online Document

2.5.1 OpenInventor in FreeCAD’s ViewProvider

The geometry that appears in the 3D views of FreeCAD are rendered by the Coin3D library. Coin3D is an implementation of

the OpenInventor standard, which exempt you from OpenGL coding.

FreeCAD itself features several tools to see or modify openInventor code. For example, the following Python code will show

the openInventor representation of a selected object:

obj = FreeCAD.ActiveDocument.ActiveObject

viewprovider = obj.ViewObject

print viewprovider.toString()

2.5. LEARNING OPENINVENTOR/COIN3D 15

2.5.2 Important classes in OpenInventor/Coin3D

SoPath, SoNode, SoEngine

are three main categories of Object in Coin3D. Classes are organised into modules, see http:

//developer90.openinventor.com/APIS/RefManCpp/main.html

Description from this online documentation is extracted for key classes. See the brief description for classes: http://coin3d.

bitbucket.org/Coin/annotated.html;

** Basic objects **

•

SbXXX: Basic types like SbVec3f, SbMatrix, SbColor, SbString, SbTime; Containers like SbDict, SbList; geometrical

representation of basic shape like SbSphere; SbTypeInfo

• SoBase: ancester for most Coin3D ojbects, similar with QObject, FreeCAD’s Base::BaseClass

Top-level superclass for a number of class-hierarchies. SoBase provides the basic interfaces and methods for doing

reference counting, type identiﬁcation and import/export. All classes in Coin3D which uses these mechanisms are

descendent from this class

ref() unref() getName()

virtual SoType getTypeId (void) const =0

notify (SoNotList *nl) //observer pattern, notify Auditor

addAuditor (void *const auditor, const SoNotRec::Type type)

Qobject is the base object for all derived Qt objects, oﬀering event, containner, property, type support.

Example of inheritance chains:

Coin3D:

SoBase->SoFieldContainer->SoNode->SoGroup->SoShape

FreeCAD:

BaseClass->App::PropertyContainer->App::DocumentObject->Part::Feature

•

SoType: Inventor provides runtime type-checking through the

SoType

class.

node->getTypeId().getName();

like

Base::TypeClass in FreeCAD

Basis for the run-time type system in Coin3D. Many of the classes in the Coin3D library must have their type

information registered before any instances are created (including, but not limited to: engines, nodes, ﬁelds, actions,

nodekits and manipulators). The use of

SoType

to store this information provides lots of various functionality for

working with class hierarchies, comparing class types, instantiating objects from classnames, etc etc

• SoField: Top-level abstract base class for ﬁelds serializable, similar with App::Property in FreeCAD

Fields is the mechanism used throughout Coin for encapsulating basic data types to detect changes made to

them, and to provide conversion, import and export facilities. SoSFXXX: Single Field with Base type wrapped

(App::Property); SoMFXXX: Multiple Field (array of ﬁeld). E.g. SoSFBool class is a container for an SbBool

value.

• SoFieldContainer: serializaton(App::PropertyContainer in FreeCAD) function is built into SoNode

• SoBaseList Container for pointers to SoBase derived objects.

The additional capability of the SoBaseList class over its parent class, SbPList, is to automatically handle

referencing and dereferencing of items as they are added or removed from the lists

** Scene organisation **

•

SoDB: This class collects various methods for initializing, setting and accessing common global data from the Coin

library

Similar with

App::Document

in FreeCAD import and export into ﬁle. Directed Acyclic Graph is used for better

performance, SoNodes are organised into database, serialization into text ﬁle *.iv .

“The foundation concept in Open Inventor is the”scene database" which deﬁnes the objects to be used in an

application. When using Open Inventor, a programmer creates, edits, and composes these objects into hierarchical

3D scene graphs (i.e., database). " Quoted from Open Inventor reference.

• SoNode: similar with App::DocumentObject in FreeCAD, has ﬂags like ignore, override

Base class for nodes used in scene graphs. Coin is a retained mode 3D visualization library (built on top of the

immediate mode OpenGL library). “Retained mode” means that instead of passing commands to draw graphics

primitives directly to the renderer, you build up data structures which are rendered by the library on demand

• SoGroup: similar with App::DocumentObjectGroup in FreeCAD

2.5. LEARNING OPENINVENTOR/COIN3D 17

An

SoSwitch

node is exactly like an SoGroup except that it visits only one of its children.

SoShape

is derived

from SoGroup Shared Instancing: share the SoShape, but seperate SoTransform, ref counting

•

SoSeperator: State-preserving group node (derived from

SoGroup

), conprising SoColor, SoMaterial, SoTexture, SoShape,

etc.

Subgraphs parented by SoSeparator nodes will not aﬀect the previous state, as they push and pop the traversal

state before and after traversal of its children. Order (topdown, left to right) in SoDB (scene graph) is important

to determine rendering, see exmaple in http://developer.openinventor.com/content/34-creating-groups. Scale node

is only added to ﬁrst Hydrogen SoGroup, but this scale applied to the second Hydrogen SoGroup. To isolate

the eﬀects of nodes in a group, use an SoSeparator node, which is a subclass of SoGroup . Before traversing

its children, an SoSeparator saves the current traversal state. When it has ﬁnished traversing its children, the

SoSeparator restores the previous traversal state. Nodes within an SoSeparator thus do not aﬀect anything above

or to the right in the graph.

•

SoPath: Container class for traversal path for nodes in scene database, see also

SoFullPath, SoNodeKitPath

. It is

derived from SoBase, not SoFieldContainer, it is diﬀerent from App::PropertyLink in FreeCAD.

“SoPath objects contain a list of SoNode pointers and a list of child indices. Indices are necessary to disambiguate

situations where a node uses the same node as a child multiple times. Similarly, UUID and getUniqueName() in

FreeCAD make the unique reference to Document Objects.”

•

SoBaseKit: base class for all NodeKit (not a SoGroup) which create groups of scene graph nodee. Parts are added as

hidden children, accessable only by the methods of SoBaseKit and its derived classes.

•

SoSeparatorKit: A nodekit that is used for creating nodekit hierarchies. SoSeparatorKit contains a transform part, a

childList part, and a few others like pickStyle , appearance in its catalog.

** Scene rendering **

• SoAnnotation: (Derived from SoSeparator) node draws all its child geometry on top of other geometry.

This group-type node uses delayed rendering in combination with Z-buﬀer disabling to let its children transparently

render their geometry on top of the other geometry in the scene.

•

SoShape: SoCube/SoCone/SoCynlinder/SoSphere/SoText/SoImageSoNurbsCurve/SoNurbsSurface/SoImage:

(App::GeoFeature in FreeCAD??)

For rendering basic shpapes.Insert a shape into the scenegraph and render with the current material, texture and

drawstyle settings (if any, otherwise the default settings are used)

• SoDetail: Superclass for all classes (SoCubeDetail. . . ) storing detailed information about particular shapes.

Detail information about shapes is used in relation to picking actions in Coin. They typically contain the relevant

information about what particular part of the shape a pick ray intersected with

** misc objects **

•

SoEngine: SoEngine (derived from SoFieldContainer, as a sibling of SoNode) is the base class for Coin/Inventor engines.

Engines enables the application programmers to make complex connections between ﬁelds, for example, animation.

• SoVRMLXXX: VRML ﬁle import and export

• SoAudioDevice: 3D sound

• SoSensor: for scene manipulation

• SoCamera: belongs only to scene

• SoLight: belongs only to scene

• SoEnvironment: gloable settings

• ScXml: Namespace for static ScXML-related functions

• SoElement: base class for classes used internally for storing information in Open Inventor’s traversal state list.

• SoSelection: Manages a list of selected nodes, Derived from SoSeparator.

Inserting an SoSelection node in your scene graph enables you to let the user “pick” with the left mousebutton to

select/deselect objects below the SoSelection node

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