How to Convert DWG to OBJ: Best Procedure for 3D Modeling CAD Drawings

Table of Contents

• What are DWG and OBJ?

• Benefits of converting DWG to OBJ

• Preparation and precautions before conversion

• Method 1: Convert DWG to OBJ using online services

• Method 2: Export DWG to OBJ with CAD software

• Method 3: Convert DWG to OBJ with free tools

• Simple surveying with LRTK

• Frequently asked questions

This article explains how to convert widely used CAD drawing data in a DWG file into the 3D model format OBJ file. Converting DWG to OBJ is the process of turning 2D plans or 3D CAD data into solid models that many 3D CG applications and viewers can handle. This article details the benefits, concrete procedures, and precautions for that conversion. It also touches on simple surveying with LRTK as an approach to generate 3D models from the field when existing drawings are not available, offering tips for 3D modeling in cases where CAD drawings are absent.

What are DWG and OBJ?

DWG (drawing) is a file format for drawing data that is standard in the CAD field. It can contain 2D design drawings such as architectural or mechanical plans, and in some cases 3D geometry data as well. Design information such as lines, curves, dimensions, and layer structures is recorded in detail, and it is treated as a de facto industry-standard format by many CAD software packages.

On the other hand, OBJ is a common file format for storing 3D model geometry. Represented by the extension `.obj`, it describes 3D shapes as polygon meshes (collections of vertices and faces). It can be accompanied by an associated `.mtl` file containing material colors and texture coordinates, and is widely used in 3DCG software and game engines. OBJ has a relatively simple, text-based structure and is valued as an intermediary format for exchanging data between different applications.

To summarize the differences between DWG and OBJ, DWG mainly contains vector data for design (lines, surfaces, solids, etc.), whereas OBJ contains polygon mesh data for display and rendering. DWG files often include CAD-specific information (for example annotations and layer names), but when converted to OBJ the output is essentially geometry (face data) only. For this reason, CAD drawings (DWG) cannot be used directly in many 3D viewers or game engines, but if converted to OBJ they can be opened in a wide range of 3D tools.

Benefits of converting DWG to OBJ

Converting CAD drawing data into OBJ 3D models enables you to share designs in three-dimensional visuals even with non-technical people. Here are some main benefits of converting DWG to OBJ.

• Visualizing designs in 3D: Shapes that are hard to understand from 2D drawings become clear at a glance in 3D models. For example, extruding walls and heights from architectural plans into 3D allows you to view the finished form in VR or present clients with a three-dimensional impression. OBJ models are an effective way to intuitively communicate design intent.

• Usable across many applications: The OBJ format is supported by many 3D software packages and platforms. Team members who do not have dedicated CAD software can open OBJ models with free 3D viewers or CG software. This makes data sharing within a team easier, and when delivering files to contractors or clients, OBJ allows them to view and use the data regardless of their environment.

• Use for 3D printing and simulation: OBJ files can also be used as data for 3D printers. Although STL is more common, OBJ can include color information which can be advantageous for 3D printing. Converting CAD-designed parts to OBJ lets you run fabrication simulations or import them into slicing software for printing, smoothing the workflow from design to prototyping.

• Use in AR/VR and game engines: In architecture and civil engineering, it is increasingly common to overlay projected completions in AR at a site or to visualize interactively in a game engine. Converting DWG drawings to OBJ makes it easy to incorporate them into AR/VR content. Converting to OBJ expands the possibilities for utilizing design data.

In short, converting DWG to OBJ realizes “3D modeling of CAD data” and enables design information to be used in a wider variety of contexts.

Preparation and precautions before conversion

Before actually converting DWG to OBJ, there are several points you should check. Proper preparation and precautions can help prevent conversion failures and unsatisfactory results.

• Confirm whether the drawing is 2D or 3D: First, determine whether your DWG contains three-dimensional geometry. If the DWG is purely 2D (plan or section drawings), converting as-is will only produce flat models without thickness. If you want a solid object, you need to perform modeling operations in CAD software before conversion (for example extruding walls or columns). If the DWG contains 3D solids or surfaces, those will be converted to polygon meshes and exported to OBJ. For curved surfaces, if you do not set the mesh density appropriately, the converted geometry may appear faceted.

• Clean up unnecessary information: Remove elements in the drawing that are not needed for 3D modeling, such as dimension lines, annotations, and title blocks. If the drawing uses layers, display only the necessary layers (geometry) and hide or delete the rest. This keeps the resulting OBJ simple and prevents unwanted lines or text objects from being included.

• Check units and scale: It is important to know which unit system the CAD drawing uses. If a DWG designed in millimeter units (mm) is converted to OBJ, the values in the OBJ will be output as millimeter values. However, if the receiving software interprets them as meters, an actual 1000 mm (39.37 in) could become 1000 m (3280.8 ft), causing the scale to be incorrect. Because the OBJ format itself does not include unit information, you must understand what one unit represents. You may need to scale the drawing data before conversion or adjust the scale in the target software after conversion.

• File format compatibility: Confirm whether the conversion tool you plan to use supports the DWG version you have. DWG formats are updated by year, and older software may not open newer DWG files. If necessary, save the DWG from a CAD program in an earlier version or export to DXF. Also, if the drawing contains external references (XREF), bind or integrate those referenced files before conversion; otherwise parts may be missing in the output.

• Data size and model complexity: When converting DWGs that include 3D geometry, the resulting OBJ may have a very large polygon count. Highly subdivided surfaces can reach millions of polygons, making file sizes huge and loading times long. If high detail is unnecessary, simplify geometry in CAD or reduce surface subdivision to control data size. Conversely, if you require detailed output, ensure you have adequate PC specs and viewer software.

With these points in mind, once you are ready you can move to the actual conversion steps. Below are three approaches for converting DWG to OBJ.

Method 1: Convert DWG to OBJ using online services

A convenient way that requires no installation is to use an online file conversion service. Several web services will convert DWG files you upload into OBJ format. This is useful when you lack specialized software and want to quickly check conversion results via a browser.

Typical steps for using an online service:

• Access a conversion site: First, find an online service that supports DWG→OBJ conversion. Searching the web for terms like “DWG OBJ online convert” will yield multiple options.

• Upload the DWG file: Specify your DWG file by using the site’s “select file” button or drag-and-drop area to upload.

• Set the output format to OBJ: Most services have a menu to choose output formats—select “OBJ” or “Wavefront OBJ.”

• Run the conversion: Click the convert/start button and wait for the server to process the DWG→OBJ conversion. Processing time depends on file size and the site’s performance, but it commonly finishes in seconds to tens of seconds.

• Download the result files: When conversion completes, a download link will appear. If the service provides both the OBJ file and a material file containing color information (`.mtl`), download both.

Advantages of online services: The biggest advantage is that no software installation is required and you can use them regardless of OS. Since you only need a browser, you can convert even when you cannot install software on a work PC.

Precautions: Uploading drawing data to an internet server poses confidentiality risks, so exercise caution with sensitive data. Do not upload confidential product designs or proprietary drawings to online services unless you trust the provider. Free plans may limit file size or the number of conversions per day. Conversion quality also depends on the service—complex drawings may suffer conversion errors. Always open the downloaded OBJ in a 3D viewer to verify that geometry has been correctly reproduced.

Method 2: Export DWG to OBJ with CAD software

If you have the CAD software that created the original DWG or another DWG-compatible design program, exporting directly to OBJ is the most reliable method. Many CAD packages include export or save-as functions that can output polygon models.

Typical procedure:

• Open the DWG in CAD software: Open the DWG in your CAD application and verify that 3D solids or other geometry display correctly. If the file is only 2D, model the 3D geometry at this stage as needed.

• Choose the export function: Select “Export” or “Save As” from the menu.

• Specify OBJ format: From the file type list, choose “OBJ (.obj)” or “Wavefront OBJ.” If your software does not support OBJ export natively, consider installing a plugin or using an intermediate format (described below).

• Configure export options: If a detailed export settings dialog appears, set units, scale, and mesh resolution appropriately. For curved surfaces, adjust mesh subdivision or tessellation parameters if available.

• Export the OBJ file: Execute the export. Processing time varies with model complexity; larger models take longer.

• Verify the results: Open the exported OBJ in a 3D viewer or other 3D software to check for geometry errors. If necessary, tweak export settings and repeat.

Advantages of direct export: This method tends to preserve the fidelity of the original CAD data. Line colors and layer names may be carried over as material names in OBJ, and official CAD software interprets drawing elements correctly before converting, resulting in high conversion accuracy.

If OBJ is not available: If your CAD software cannot export OBJ directly, alternative workflows include:

• Exporting once to STL (a format for 3D printing) and then converting the STL to OBJ. Since STL is a polygon mesh format, geometry is preserved and many free tools or online services can convert STL→OBJ.

• Exporting to 3DS or FBX and converting those to OBJ on the receiving side. FBX is widely supported for 3D and animation, so using FBX as an intermediate format can simplify subsequent conversion to OBJ.

If you do not have the software: Some users do not have DWG-capable CAD software. In that case, using a trial version of commercial CAD software for a short period can work. Many commercial CAD packages offer free trial periods of several weeks, which you can install to try the export procedure. Observe the license terms and use trial software for evaluation purposes only.

Method 3: Convert DWG to OBJ with free tools

Even without expensive commercial software, you can convert DWG to OBJ using only free tools in some workflows. Open-source and freeware CAD programs and viewers often include conversion features between different CAD formats.

For example, some open-source 3D CAD tools can import DWG or intermediate DXF and export OBJ. There are also free utilities provided by organizations that specialize in CAD data conversion. Below is a general flow for using free tools.

• Obtain a free CAD viewer/converter: First, install free software that can open DWG files, such as open-source 3D CAD tools or DWG-compatible free viewers available online.

• If necessary, convert DWG to DXF: Some free tools cannot read DWG directly. Converting DWG to DXF first can increase compatibility. DXF is a text-based format equivalent to DWG and is widely supported. Free DWG→DXF converters are available.

• Open the drawing in the software: Load the DWG (or DXF) into the free program. If it does not display correctly, check for missing plugins or version compatibility.

• Export to OBJ: Once the data opens, use the program’s “Export” or “Save As” function to write out an OBJ file. The menu item may read “Wavefront (.obj)”. Adjust settings such as units and mesh quality if options are provided.

• Check the output: After export, open the resulting OBJ in another viewer to confirm it matches the expected 3D geometry.

Advantages of free tools: No monetary cost and the ability to work offline are key benefits. Since data stays local, there is no risk of leakage to external servers. Once you set up the environment, you can reuse it for various CAD data conversions.

Precautions: Free software may have idiosyncratic operations and limited Japanese-language resources. Initially you may need trial-and-error and consult online communities or manuals to set parameters. Conversion quality depends on the tool; sometimes dimensions may not convert accurately or tessellation controls may be limited. If one tool fails, try another tool.

If you are comfortable with programming, you can also use CAD conversion libraries or scripts to batch-convert DWG to OBJ; however, that approach is beyond the scope of this article for general users.

Simple surveying with LRTK

So far we have covered creating OBJ 3D models from existing DWG drawings. But what if you do not have drawings at all, or you want to model the current building or terrain as-is? An increasingly popular solution is simple surveying with LRTK.

LRTK is a small surveying device that can be attached to a smartphone. It uses high-precision GNSS (Global Navigation Satellite System) and RTK (Real-Time Kinematic) technology and works with a phone to achieve centimeter-level high-precision positioning (cm level accuracy (half-inch accuracy)). Combined with a smartphone’s built-in LiDAR sensor (laser-based ranging), it is designed so that anyone can easily capture surrounding 3D data (point clouds).

Traditionally, obtaining detailed 3D site geometry required a survey team with large equipment, expensive 3D laser scanners, or photogrammetry from drones. With LRTK-based simple surveying, one person can collect site geometry data in a short time. Specifically, attach the LRTK device to a smartphone, enter survey mode, and walk around the target; walls, ground, and structural surfaces are recorded as a cloud of points (point cloud data). Because LRTK continuously records its precise position, the captured point cloud is georeferenced with coordinates and elevation, so it is clear later exactly where each data point was taken.

You can generate polygonal 3D models from the captured point cloud. If you mesh the point cloud with dedicated software, you obtain accurate OBJ models based on real measurements of buildings and terrain. If existing drawings are outdated or do not reflect current conditions, LRTK surveying allows you to create models that reflect the field’s up-to-date information.

LRTK-based simple surveying is attracting attention as an innovative method supporting DX (digital transformation) in construction and civil engineering. It is easy to operate for less experienced technicians, compact and portable, and its use is expanding from pre-renovation surveys to construction records and equipment inspections. Whether or not you have DWG drawings, having the option to collect field data yourself with LRTK gives you the ability to create 3D models as needed, and LRTK is likely to become an increasingly common tool for simple surveying.

By combining desktop conversion of existing data with on-site data acquisition and 3D modeling, you can efficiently handle a wide range of situations.

Frequently asked questions

Q: Can I convert DWG to OBJ without dedicated CAD software? A: Yes. You can use online file conversion services to convert DWG to OBJ in the browser. You can also use open-source CAD software or free viewer tools to perform local conversions. If you don’t have specialized software, try the methods introduced in Method 1 or Method 3.

Q: Can I create a 3D model from a 2D DWG drawing? A: Simply changing the file format will not automatically create a 3D model from a 2D drawing. To make a 3D model from a 2D DWG, you need to perform modeling operations on the original drawing, such as extruding lines that correspond to walls and floors to give them height and thickness. For an architectural floor plan, for example, extruding wall lines to a height creates the building’s 3D form. Thus, 2D→3D requires the designer’s judgment to fill in missing geometry. Once you have a 3D model, you can export it as OBJ for further use.

Q: What software can open the converted OBJ file? A: OBJ is highly versatile and can be opened by many programs. Free 3D viewers and 3DCG software can import OBJ files for viewing and editing. Typical examples include modeling packages, game engine editors, and architectural visualization tools. Some operating systems include a built-in 3D viewer that can display OBJ files. Choose a viewer or editing tool that supports OBJ based on your environment.

Q: What should I watch for when converting DWG to OBJ? A: Several points to note. First, results differ greatly depending on whether the source data is 3D or 2D—if you need a 3D model, convert the drawing to 3D beforehand. Second, pay attention to unit consistency to avoid scale issues; if the scale is wrong after conversion, adjust the scale in the software that imports the OBJ. Elements specific to drawings (text, dimension lines, hatching) are generally not included in OBJ, so confirm that only the required geometry is modeled. Finally, be mindful of data confidentiality; if you use online conversion, files are transferred to third parties, so handle confidential drawings offline when necessary.

Q: If I don’t have drawing data, how can I make a 3D model from the field? A: Even without drawings, you can capture the site and create 3D data. Devices such as LRTK allow virtually anyone to acquire high-precision 3D point cloud data. By scanning the site with a smartphone and LRTK, you can record building and terrain shapes as point clouds. From those point clouds you can generate polygonal models (OBJ files, etc.), so you can obtain an up-to-date 3D model even without drawings. Tasks that used to require specialized vendors can now be performed more efficiently in-house using LRTK-based simple surveying.