Comparison of development modes between AutoCAD ActiveX and RhinoCommand

Official Account: Non-Deconstructive · Author: Zhou Wenqi (Venchy)

Many friends are very interested in the secondary development of AutoCAD.With the gradual rise of parametric design, the use of Rhino in architectural design has gradually become a trend.The editor started learning AutoLisp many years ago and has written many AutoLisp scripts commonly used in work. In recent years, he has started to contact Rhino and tried secondary development of grasshopper and Rhino.It was found that the two softwares are not only similar in function, but also have many similarities from the perspective of development and software architecture.So they can be compared together.For these software, if you look at the operation level, everyone may be familiar with it, but you don’t know enough about the deeper content of the software itself. Based on so many years of script writing or secondary development experience, I feel that understanding these two software from the architectural level can actually be of great benefit to our work.The purpose of writing this article is to help everyone gain a deeper understanding of the two software through a comparative introduction to the secondary development of the two software. Even if you do not do secondary development, you can get some inspiration from it.Although AutoCAD also has secondary development methods such as .net, ObjectARX, etc., in order to make the comparison more intuitive, the editor chose ActiveX, which is relatively basic and easy to understand.

1. Configuration of software development environment

Both software officially have very complete development manuals. AutoCAD： http://help.autodesk.com/view/OARX/2018/ENU/

The main references for the development of ActiveX are: (1) ActiveX Developer’s Guide (ActiveX/VBA), mainly a development method documentation. (2) ActiveX: reference Guide, mainly a description of the ActiveX configuration file library.

RhinoCommon： https://developer.rhino3d.com/

Development introduction: https://developer.rhino3d.com/guides/rhinocommon/ API documentation: https://developer.rhino3d.com/api/RhinoCommon/html/R_Project_RhinoCommon.htm

Configuration of AutoCAD development environment: The editor first created a .net framework console application.After the creation is completed, add the AutoCAD secondary development configuration file in the reference of the console:

Reference the two files acax22enu.tlb and axdb22enu.tlb in the AutoCad installation directory C:\Program Files\Common Files\Autodesk Shared. The 22 here is the version number of AutoCAD2018. For other versions, follow the development instructions and so on.After the reference is completed, two reference library files, AutoCAD and AXDBLib, appear at the referenced location.In this way, the AutoCAD ActiveX development environment in .net has been configured. Rhino development environment configuration: Under the extension menu bar of Visual Studio, click Manage Extensions, search for RhinoCommon under Online, install this plug-in, and restart Visual Studio. At this time, the new Visual Studio project will contain the corresponding RhinoCommon development template.After creating the project according to the template, the development environment is configured by itself.

2. Obtain software objects through programs

The AcadApplication class at this time is the current AutoCAD program.

In Rhino, the currently running rhino program can be obtained directly through the Rhino namespace.There are two classes under the Rhino namespace, one is RhinoApp and the other is RhinoDoc, which control the program’s sections and internal files respectively.

3. Software data structure

After obtaining the software object, we need to give a certain introduction to the data structure of the software, which will be helpful whether it is for secondary development or for our daily use. First of all, for AutoCAD, any dwg drawing is a database, and each dwg database contains corresponding graphic data.For example, Layer Table stores the data of all layers, Block Table stores the data of blocks, and so on.

For an AutoCAD application, it is necessary to read the contents of this database and then place it in the memory space occupied by the current program.The data structure of this program in the memory space is as shown below:

An application contains Preferences, Documents, MenuBar and MenuGroups.Among them, Preferences, MenuBar and MenuGroups are some contents related to software settings, which we don’t use frequently.The main graphics files are stored in Documents.The concept of Documents here is the many dwg drawings opened by the software.Any Document in Documents is one of the dwg drawings. Let’s take a look at the development instructions for Documents （http://help.autodesk.com/view/OARX/2018/ENU/?guid=GUID-2C8C8291-16C9-4A9F-8399-58D5DE4B9589#GUID-2C8C8291-16C9-4A9F-8399-58D5DE4B9589）：

It contains four methods: Add, Close, Item, and Open, which means that we can create, close, switch, and open dwg drawings through the program.

The figure below shows the process of opening a drawing using code.

After opening the dwg drawing in CAD to obtain each Document, the Document contains, for example, all model spaces, paper spaces, and their primitives, layer information, block information, etc., and these data can be obtained and modified through code. For Rhino, there is a similar mechanism to access the graphics data in each 3DM file.The RhinoDoc class in Rhino is similar to the Document class in AutoCAD.The following is an example of opening a 3dm file under a specified path through code.Is it the same as the previous CAD code?The RhinoDoc class also contains a series of elements such as layer list, tile list (referenceInstance), primitive list, etc.For detailed instructions in the RhinoDoc class, please refer to the official development documentation: （https://developer.rhino3d.com/api/RhinoCommon/html/T_Rhino_RhinoDoc.htm）

So to a certain extent, the data formats of AutoCAD and Rhino are actually very similar.Next, we will compare the development processes between Rhino and AutoCAD through several actual scenarios.

4. Select graphics elements

In AutoCAD’s ActiveX, each Document contains a SelectionSets class, and this SelectionSets contains many SelectionSets.We can use this SelectionSet to select the objects we need to edit.The contents of each SelectionSet are as follows:

Among them, Select, SelectAtPoint, SelectByPolygon, SelectOnScreen is a few ways to select.The following code obtains an instance of an object through the Select method:

The meaning of filter and filterData refers to the straight line whose filter layer is S-BEAM-LINE2.For detailed instructions on element filtering, please see the following website: http://help.autodesk.com/view/OARX/2018/ENU/?guid=GUID-4CDE43DD-E3EF-4EF8-B377-4B9ED03E4C96 http://help.autodesk.com/view/OARX/2018/ENU/?guid=GUID-6026DE9A-DC00-46D2-938A-6EDCD8670578 After obtaining the selected object, the entity in the traversal selection is the entity we selected. Next, we can modify the entity we selected. Selecting primitives in RhinoCommon is a similar operation.The following code is the code for RhinoCommon to select primitives. Among them, GetObject is the selection class. By setting certain filtering conditions through GetObject, and using the method to obtain the object, the selection of the object can be realized.

However, the geometryFilter cannot set the layer options, so at this time, we need to use another method to obtain the primitives through the layer.

5. Create primitives

As mentioned before, all primitives in AutoCAD are placed in a table, and we can edit the primitives on the drawing by accessing the table. In AutoCAD, each Document has a corresponding ModelSpace, which is what we call drawing space. ModelSpace provides many methods so that everyone can create various primitives in it.You can refer to the following URL (http://help.autodesk.com/view/OARX/2018/ENU/?guid=GUID-C541B6F2-1279-4D1C-8DC0-788F27F644EF#GUID-C541B6F2-1279-4D1C-8DC0-788F27F644EF), the methods provided are as follows:

Let’s take creating a straight line as an example.

By creating the corresponding points and using the Addxxx method under ModelSpace, we can easily add the corresponding graphic elements to the CAD drawing space. Similarly, we can also get the layers table of the current document and add new layers through the Add method of the layers table.

For Rhino, we can also create new primitives by accessing the corresponding table.There is an Objects table under RhinoDoc, which contains all graphic elements in the current 3dm graphic file.The Objects table itself is an ObjectTable class, which also provides many methods for adding graphics elements (https://developer.rhino3d.com/api/RhinoCommon/html/T_Rhino_DocObjects_Tables_ObjectTable.htm).

Let’s still take adding a straight line as an example to create a straight line in Rhino through RhinoCommon:

This code is exactly the same as the way CAD creates straight lines. In addition, RhinoDoc also contains LayerTable for example, and we can also create a Rhino layer through RhinoCommon.

6. Modify graphics elements

Currently, we can create primitives and select primitives. So, how do we modify the primitives?Take modifying the endpoint of a created line as an example. In AutoCAD, we only need to obtain the Line object, and then simply replace the endpoint of the line by reassigning the endPoint of the line.

In RhinoCommon, you can also modify the endpoints of primitives in the same way:

7. Delete primitives

In AutoCAD, any graphic element inherits from the AcadObject class. This class has its own Delete method. We only need to simply obtain the object that needs to be deleted and call the delete method to delete the graphic element.The code is very simple, only one line.

In Rhino, we need to delete the object by calling the delete method in RhinoObjectTable.There are multiple overloads of this delete method:

We choose one of the methods to delete the corresponding object.Or just a simple line of code.

8. Summarize

The code examples in this article are actually very simple, and students without programming foundation may be able to get an overview.The purpose of writing this article is to help everyone understand these two software through comparison from the perspective of secondary development.In fact, these two softwares are very similar, and the editor also thinks that he has a certain understanding of these two softwares. AutoCAD and its supporting work models have been dominating the domestic architectural design industry since the 1990s, while Rhino slowly became a trend after parametric design in architectural design became popular around 2010.From the perspective of everyone’s design habits and corresponding derivative products, it is natural that AutoCAD currently dominates the world.Judging from the editor’s experience of playing these two softwares for so many years, Rhino may still lack some configurations related to drawings in the architectural design industry, and some functions such as drawing management have yet to be developed.But from the perspective of element management, Rhino’s layout is more flexible. First of all, Rhino is based on OpenNurbs, and its graphic expression ability is far stronger than AutoCAD.Secondly, Rhino has a richer API interface, and users can more easily obtain the data they need from Rhino through programming.Once again, the grasshopper that matches Rhino greatly enhances Rhino’s capabilities.In addition to developing based on RhinoCommon, users can also develop based on grasshopper.In addition, the graphics data of Rhino and AutoCAD are completely matched, and the two can be converted to each other. Of course, this does not mean that Rhino can completely replace AutoCAD. However, the editor feels that the two can have a symbiotic relationship. Obtaining Rhino’s ability to quickly edit and generate graphics and batch processing, combined with AutoCAD’s advantages in traditional design workflows, may also be an option.

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This document is automatically collected and organized by AI from non-deconstructed public accounts and is for learning reference only.

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