DWG and OBJ Format Conversion Guide: How Designers Should Use 3D Data

Table of Contents

• What are DWG and OBJ?

• Differences between DWG and OBJ

• Reasons and benefits for converting DWG to OBJ

• How to convert DWG to OBJ

• Precautions and key points during conversion

• How to use converted 3D data

• Using simple surveying with LRTK to enable 3D data use

• FAQ

What are DWG and OBJ?

First, a brief explanation of the two file formats, DWG and OBJ. DWG is a drawing file format mainly used by CAD (computer-aided design) software. It is a standard format used across many architectural design and manufacturing fields and can store 2D drawings and 3D models. On the other hand, OBJ is a format that records 3D model geometry, representing three-dimensional shapes as polygon meshes (collections of polygons). The OBJ format is widely used in CGI production, 3D rendering, game development, and as an interchange format for 3D data between different software.

For designers, DWG is a reliable format that can precisely define drawings and models, but it can be difficult to handle outside of CAD software. OBJ, however, is a highly versatile format that almost all 3D-related software can import. Because OBJ stores geometry as a collection of polygons, it does not include CAD-specific dimensions, annotation data, or parametric information. Each format has its strengths, and by converting between them as needed, you can make design data usable across a wider range of workflows.

Differences between DWG and OBJ

There are several differences between the DWG and OBJ formats in terms of purpose and content. The main distinctions are summarized below.

• Data structure differences: DWG stores geometry in vector form such as lines, curves, surfaces, and solids. OBJ describes shapes in mesh form using points (vertices) and faces (polygons). In other words, DWG can mathematically define design elements, while OBJ defines shapes as collections of fine triangles or quadrilaterals.

• Use cases and fields: DWG is mainly used for drawings and models that require high accuracy, such as architectural blueprints and mechanical part drafting. OBJ is widely used for visual 3D model exchange in rendering, game development, and AR/VR. When designers need to share models with other fields, converting DWG to OBJ makes 3D models easier to share.

• Information content: DWG files include metadata necessary for design, such as layer information, dimensions and annotations, and blocks (assemblies of parts). OBJ files primarily contain pure geometry information, and material data is only simply defined in a separate .mtl file. Therefore, when converting from DWG to OBJ, drawing-specific annotations and dimension symbols will not be preserved.

• Units and scale: DWG typically uses drawing units (mm (in) or inch, etc.) for design, but OBJ itself does not have an explicit concept of “units.” When opening an OBJ file in other software, what one unit represents (e.g., how many mm) depends on the software’s settings. Therefore, when converting DWG to OBJ, export at an appropriate scale and verify unit settings on the receiving side.

• Accuracy and shape representation: In DWG, circles and curved surfaces are retained as mathematically exact shapes, whereas in OBJ they are represented as polygonal meshes. During conversion, curves become collections of fine straight segments, and the original geometric precision can be reduced. It is important to adjust mesh subdivision (polygon count) as needed to reproduce smooth shapes.

• Editability: DWG data can be easily edited in CAD software with dimension changes or constraints. OBJ is a completed polygon model; to modify geometry you must manipulate polygons in 3D modeling software. If design changes are likely, keep the original DWG and reconvert as needed.

Reasons and benefits for converting DWG to OBJ

There are many situations where designers convert DWG data to OBJ. The benefits gained from such format conversion include:

• Viewable and usable in a wide range of software: Because OBJ is a general-purpose format, people without specialized CAD software can open models with free 3D viewers or other design tools. This makes it easier to share with clients or other departments and reduces communication costs.

• Realistic visualization: Converting to OBJ allows you to import models into 3D rendering software or game engines to produce high-quality images and videos. Visualizing design-stage models photorealistically helps stakeholders understand the final appearance and facilitates feedback.

• Use in AR/VR and simulations: OBJ data can be easily used in AR apps and VR systems to overlay design models onto real space. Mesh models can also be used in analysis software for simple structural or thermal simulations.

• 3D printing and manufacturing: Converting 3D shapes to OBJ (or similar formats like STL) enables 3D printing of prototypes or creating verification models for digital fabrication machines. Using CAD data directly to obtain physical prototypes becomes more straightforward.

• Cross-discipline collaboration: OBJ can act as a common language when sharing DWG data with CG designers, programmers, and other specialists. Each team can use their preferred tools while referring to the same 3D data, smoothing collaboration.

How to convert DWG to OBJ

Below are general procedures for converting DWG data to OBJ. Depending on your situation there are several approaches; the representative methods are introduced here.

• Export from the original CAD software: The most reliable method is to use the export function in the CAD software that created the DWG. Modern 3D-capable CAD programs often have “Save As” or “Export” menus that can write OBJ format (or other intermediate 3D formats). If the software does not support direct OBJ export, you can export to another interchange format (for example STL or FBX) and then convert that to OBJ.

• Use dedicated conversion tools or plugins: If you don’t have the CAD software that created the DWG or don’t have DWG-capable software, use file conversion software. Open-source 3D modeling tools and viewers that are free may support reading DWG or intermediate formats and exporting OBJ. Commercial CAD conversion tools or plugins can also add OBJ export functionality to some CAD packages. Note that plugins require the host software’s license and environment.

• Use online conversion services: A convenient option is to upload DWG files to a web conversion service to convert to OBJ. This requires no software installation and is browser-based, but be mindful of the risk of uploading sensitive design data to third-party servers. Check the service’s trustworthiness and, if necessary, consider password-protecting files or other precautions.

• Verify conversion results: Regardless of the method, open the resulting OBJ in a viewer or target 3D software to confirm the geometry is correctly reproduced. Check that curved surfaces and fine details are properly meshed and that the scale (size) matches the original dimensions. Adjust export settings (mesh density, etc.) and reconvert as needed to improve quality.

Precautions and key points during conversion

When converting DWG to OBJ, there are several important points to ensure smooth use.

• 2D drawings do not automatically become 3D: If the DWG contains 2D drawings, converting to OBJ will produce flat, thickness-less geometry. Lines that are not modeled in 3D will remain as line segments, so perform extrusion (solidification) or surface creation before conversion if you need 3D shapes.

• Handling layers and part structure: Complex DWG files may contain many layers and blocks (parts). Whether these become merged mesh objects or separate objects in OBJ depends on the software. If you want to manipulate model components individually after conversion, check whether the export settings can preserve groupings (for example, split objects by layer).

• Check unit scale: As mentioned earlier, OBJ has no unit metadata, so models may be exported at unexpected sizes. For example, if a CAD model used mm (in) units and the OBJ is interpreted by another program as “1 unit = 1 m (3.3 ft)”, the model could appear enormous. Always verify model size before and after conversion, and adjust export scale or the import-side scale as necessary.

• Coordinate offset issues: If a DWG model was drawn far from the origin (0,0,0), converting to OBJ may reset position information and place the model near the origin, or it may preserve very large coordinate values. In the first case, be careful to maintain alignment with other reference data; in the latter case, some viewers may experience precision issues. If needed, move the model closer to the origin before exporting.

• Polygon count and detail: If the resulting mesh has an excessive polygon count, the file size can become unwieldy. Converting CAD details such as screw threads or tiny chamfers into polygons can produce millions of polygons. If the exporter allows adjusting mesh density, set an appropriate level for the intended use. Conversely, too low a polygon count will make curved surfaces appear faceted, so balance detail and performance according to the use case.

• Color and material information: Colors or materials assigned in DWG are generally not carried over to OBJ (at best, simple color info may be placed in a companion MTL file). For realistic rendering, you will need to reassign materials and textures in the 3D software after importing OBJ. However, assigning distinct colors to objects before conversion can help as a guide for grouping or material assignment afterward.

How to use converted 3D data

3D data obtained by converting DWG to OBJ can be used in many design scenarios. Below are the main use cases designers should know.

Presentations and design reviews

Converted OBJ models are powerful visualization tools for design reviews and presentations. For example, you can set up lighting and materials in a rendering application to create realistic images of the finished product, or create simple animated videos to convey concepts. Spatial volume and material qualities that are hard to grasp from plans and sections become clear in 3D. Integrate models into client presentation materials, share your screen in online meetings to discuss the 3D model, and improve communication quality.

Spatial verification with AR/VR

OBJ data can be used for design checks using AR (augmented reality) and VR (virtual reality). Load the model into an AR app on a tablet or smartphone to overlay the design on the real environment. For example, in an office renovation you can visit the site and use a tablet to place a 3D model of the new layout, easily checking scale and arrangement. Using a VR headset lets you virtually walk through the unbuilt interior to evaluate spatial experience. All of these uses are enabled by preparing OBJ models from DWG drawings.

Creating physical models (3D printing, etc.)

One way to turn digital data into physical models is 3D printing. Convert CAD parts or architectural massing models to OBJ, then use slicer software to generate print data (STL, etc.) and fabricate prototypes. Quickly produce palm-sized prototypes for functional or design evaluation, or build architectural models for stakeholder review—OBJ supports a smooth digital-to-physical workflow. Combining mesh models with laser cutters or CNC machines to fabricate parts is also possible. OBJ serves as a foundation for various prototyping methods.

Integration with site data

There is increasing opportunity to combine site-derived 3D data with design models. For example, overlay design OBJ models with point clouds from drones or laser scanners, or with photogrammetry-generated OBJ site models to visually confirm fit and detect clashes or gaps. For renovation projects, scanning the existing building and placing the new design model into that context is an effective method. Integrating site-sourced 3D data with design models enables higher-accuracy planning and smoother consensus building.

Using simple surveying with LRTK to enable 3D data use

A technology attracting attention for making on-site 3D data acquisition more accessible is simple surveying using LRTK. LRTK is a solution that combines a small high-precision GNSS receiver that can be attached to a smartphone with a dedicated app, enabling centimeter-level positioning/surveying (half-inch accuracy) by anyone. Tasks that previously required specialized surveying equipment can be conducted with a smartphone: you can measure points on site or capture photos to obtain highly accurate, georeferenced point cloud data.

For designers, this technology offers big advantages. For example, in a renovation project you can quickly measure current dimensions without bringing tape measures or conventional surveying gear, using LRTK to gather on-site 3D measurements. The resulting point clouds and measurement data can be compared with CAD drawings or converted to OBJ and used as background models, allowing immediate identification of discrepancies between the design plan and the existing condition. Obtaining accurate site data quickly through simple surveying improves early-stage design precision and helps prevent mistakes during construction.

LRTK-based simple surveying is expected to become increasingly widespread in design and construction. This technology promotes site digitization and seamless linkage with design data; if you’re interested, check official information for details (LRTK product page: https://www.lrtk.lefixea.com/). Adopting cutting-edge tools like this will further expand how you can use 3D data.

FAQ

Q: Does it cost money to convert a DWG file to OBJ? Can it be done for free? A: Yes, it can be done for free. You don’t need paid professional software—open-source 3D tools or online conversion services can convert DWG to OBJ. However, depending on the contents of the original DWG, commercial software may yield higher conversion fidelity or better preserve layout information. Try free methods first and, if necessary, evaluate trial versions or plugins.

Q: Will dimensions and annotations in the drawing remain after converting to OBJ? A: Unfortunately, drawing elements such as dimension lines and text annotations are not preserved in OBJ. OBJ handles only 3D geometry (vertices and faces), so drawing-specific elements are lost during conversion. Save necessary dimension info as screenshots or reapply annotations in the software after importing OBJ. To accurately convey design intent, provide the original DWG as well or supply PDF versions of drawings.

Q: Can OBJ data be converted back to DWG (CAD data)? A: Restoring an OBJ back to equivalent CAD DWG data is very difficult. OBJ is a polygon mesh and lacks CAD-style curves and dimension data, so reverse conversion won’t produce precise drawings. Some CAD or 3D software can import OBJ and save a “DWG with 3D model,” but the geometry will remain a mesh and be hard to edit as CAD entities. To fully recover DWG drawings, the reliable approach is to use the OBJ as a reference and remodel or redraw in CAD.

Q: Is STL better than OBJ for 3D printing? What’s the difference? A: STL is effectively the de facto standard for 3D printing, but OBJ often works fine as well. STL represents geometry using only triangular polygons and does not contain color or material information, whereas OBJ can handle quadrilateral polygons, vertex normals, and texture coordinates, and can be accompanied by a separate file for color/material info. If you only need to print shape in a single color, STL is sufficient; if you need color separation or textures, OBJ is more suitable. Many slicer programs prefer STL, so you may convert OBJ to STL after DWG→OBJ conversion or export STL directly if available.

Q: Circles and curved surfaces look faceted after conversion. How can I make them smooth? A: When cylinders or arches are converted to OBJ, originally smooth curves may look faceted because the mesh polygon count is too low. To address this, increase mesh subdivision (raise polygon count) in export settings to produce smoother surfaces. Adjust parameters such as “curve tessellation” or “tolerance” and re-export. You can also apply smooth shading in modeling software after conversion to improve appearance. However, increasing polygon count too much will make the data heavy, so choose a balance appropriate for the intended use.