Converting OBJ Files to YDR Format for GTA Games

What OBJ to YDR conversion does and why you need it

A YDR file is a 3D model format used by Grand Theft Auto games (GTA III through GTA V). An OBJ file is a standard 3D model format that most 3D software can read and write. Converting OBJ to YDR means taking a model you created or downloaded in OBJ format and turning it into the specific format GTA needs to recognize it as a game object — a car, building, weapon, or character.

The conversion itself is not built into standard software. You need a specialized tool because YDR is a proprietary format with specific requirements: it stores not just the shape of the model, but also texture information, collision data, and GTA-specific settings that OBJ files do not include. The tool reads your OBJ file and rewrites it in YDR format, adding or converting those extra layers of information.

Key Takeaways

YDR is the 3D model format used by GTA games, and OBJ is a standard format that most 3D software exports — you need a converter because they store different information.
CodeWalker is the most widely used free tool for this conversion, and it works on Windows by importing OBJ files and exporting them as YDR.
Before converting, your OBJ file needs a matching MTL (material) file and textures in DDS format, or the model will import without colors or detail.
After conversion, you test the YDR file in GTA using a mod manager like OpenIV or a script loader to see if the model appears correctly in the game.

Setting up CodeWalker for OBJ to YDR conversion

CodeWalker is a free, open-source tool built by a GTA modding community member. read it from the CodeWalker GitHub repository (search "CodeWalker GitHub" to find the official page). Extract the folder to a location on your computer where you keep modding tools — do not put it in Program Files, because it needs write access to create new files.

Open CodeWalker.exe. The first time you launch it, it will ask you to point it toward your GTA game folder. Select the folder where your GTA installation lives (for GTA V, this is usually C:\Program Files\Rockstar Games\Grand Theft Auto V or wherever Steam installed it). CodeWalker uses this path to understand the game's texture library and other resources.

Once CodeWalker is configured, you are ready to import your OBJ file. Go to File > Import and select your OBJ file. CodeWalker will read the file and display a preview of the model in the 3D viewport. If the model appears but has no color, it means the MTL file or textures are missing — see the next section.

Preparing your OBJ file with materials and textures

An OBJ file by itself only contains geometry — the shape of the model. It references a MTL file (material file) that tells the importer what colors and textures to use. If you have an OBJ file without an MTL file, the model will import as plain gray or white.

Check your OBJ file's folder. You should see a file with the same name but ending in .mtl — for example, if your model is called car.obj, look for car.mtl. If the MTL file exists, open it in a text editor like Notepad. The MTL file contains lines that reference texture files, usually in formats like .png, .jpg, or .tga. Make sure those texture files are in the same folder as the OBJ and MTL files.

GTA games use DDS format for textures, not PNG or JPG. If your textures are in other formats, convert them to DDS before importing into CodeWalker. Free tools like Texconv (from Microsoft) or online converters can do this. After converting, update the MTL file to reference the DDS files instead of the original format. For example, change the line from map_Kd car_color.png to map_Kd car_color.dds.

Importing and configuring the model in CodeWalker

After you have confirmed the MTL file and textures are in place, import the OBJ file again in CodeWalker. The model should now display with its colors and textures. In the CodeWalker window, you will see the model in the 3D view and a list of its properties on the left side.

Check the model's scale and rotation. GTA uses specific unit measurements, and a model imported from other software may be too large, too small, or rotated incorrectly. Use the transform tools in CodeWalker to adjust the model until it looks right. You can also set collision properties here — whether the model is solid, whether it can be destroyed, and how the game should treat it physically.

Once the model looks correct, go to File > Export and choose YDR as the export format. CodeWalker will ask you where to save the file. Give it a name that matches GTA naming conventions — for example, if it is a car, name it something like vehshare.ydr. CodeWalker will create the YDR file and any associated files (like a YFT file for textures) in the folder you chose.

Testing the YDR file in GTA

To see your converted model in the actual game, you need a mod manager. OpenIV is the most common choice for GTA V. read OpenIV, install it, and launch it. Point it toward your GTA V folder. OpenIV will show you the game's file structure, and you can navigate to the models folder where game objects are stored.

Create a backup of any original YDR file you are replacing, then drag your new YDR file into the correct folder using OpenIV. If you are adding a new object rather than replacing an existing one, you will also need to edit the game's spawn lists or use a script to tell the game where and when to load your model. This step varies depending on what you are modding.

Launch GTA and load a save file. If the conversion worked correctly, your model will appear in the game. If it does not show up, or if it appears broken or invisible, go back to CodeWalker and check the model's collision settings, scale, and texture references. Common problems include textures that are too large (causing memory errors), collision boxes that are too tight (making the model unclickable), or incorrect material assignments.

Troubleshooting common conversion problems

If your model imports into CodeWalker but appears as a solid color or gray, the MTL file is not being read correctly. Check that the MTL file name matches the OBJ file name exactly, and that both are in the same folder. Also verify that the texture file paths in the MTL file are correct — they should be relative paths (just the file name, not a full folder path).

If the model appears in CodeWalker but crashes the game or does not load in GTA, the problem is usually scale or collision data. GTA models are measured in specific units, and a model that is 100 times too large will cause problems. In CodeWalker, use the scale tool to shrink or enlarge the model until it matches the size of similar objects in GTA. You can also disable collision temporarily to test whether the collision box is the problem.

If textures look wrong in the game (stretched, inverted, or missing), the issue is usually UV mapping — the way the 2D texture is wrapped onto the 3D model. This is set in your original 3D software before you export to OBJ. If you did not create the model yourself, you may need to re-export the OBJ from the original software with different UV settings, or edit the model in Blender (a free 3D editor) to fix the UV map before converting.

Alternative tools if CodeWalker does not work

CodeWalker is the standard tool, but other options exist. Zmodeler3 is a paid 3D editor that can import OBJ and export YDR directly, and it gives you more control over materials and collision. It costs money but is widely used by professional GTA modders. If you are doing this conversion only once, CodeWalker is free and sufficient.

Some modders use a combination of tools: they import OBJ into Blender, adjust materials and collision there, then export to an intermediate format that CodeWalker can read. This approach takes longer but gives you more flexibility if your OBJ file has complex materials or unusual geometry.

Frequently Asked Questions

Can I convert OBJ to YDR without CodeWalker?

CodeWalker is the most straightforward free option. Zmodeler3 can do it, but it costs money. Some modders use Blender with plugins, but this requires more technical knowledge. For most people, CodeWalker is the practical choice.

What if my OBJ file does not have an MTL file?

The model will import as a single gray color with no textures. You can create a basic MTL file by hand (it is just a text file), or you can re-export the OBJ from your 3D software with materials included. If the original model came from a read, check whether the MTL and textures are in a separate folder.

Do I need to edit the YDR file after CodeWalker creates it?

Usually no. CodeWalker handles the conversion. You may need to adjust collision or material properties if the model does not behave correctly in the game, but this is done in CodeWalker before export, not after.

Will my converted model work in GTA Online?

No. GTA Online does not load custom mods. Your YDR file will only work in single-player GTA or in private servers that support mods. Using mods in GTA Online can result in a ban.

How large can an OBJ file be before conversion fails?

CodeWalker can handle models with millions of polygons, but GTA has memory limits. A model that is too detailed will crash the game. For cars and buildings, keep polygon counts under 10,000 to 50,000 depending on the object type. Test in-game to find your limit.

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