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Prop Model Assets

Prop Model Asset sample

Prop model assets reference external 3D model files that can be placed within the scene.


Create an asset by using one of the supported file formats shown. Then, drag the file into the RoadRunner Library Browser.

Supported Formats:

  • glTF™ (.gltf, .glb)

  • Filmbox (.fbx)

  • OpenFlight (.flt)

  • OpenSceneGraph (.osg, .osgt, .osgb, .ive)

  • Wavefront (.obj)

Refer to the Library Browser page for general instructions to create, edit, and delete assets.

Refer to Prop Tools for details on adding prop model assets to the scene.

Prop Attributes

All prop assets have a set of options that affect the way the props are placed. For example, some props will always align vertically, such as a traffic signal. Other props will align to the surface they are placed on, such as a garbage can sitting on a sloped sidewalk. (This option can be toggled on a prop-by-prop basis.) Other options include the ability to randomly rotate the prop around the vertical axis, which is useful for varying the orientation of trees and plants.

To set the default attributes for a particular prop asset, first select the prop in the Asset Browser. The prop's attributes will then appear in the Attribute Panel, where they can be interactively adjusted.

Prop Attachment Curves

An attachment curve is a spline associated with a prop that RoadRunner uses as a cue when attaching objects to each other.

As an example, note the green highlight line in the following signal pole prop. The image on the right is a close-up that shows this detail.

When you pick another prop from the Library Browser and bring it sufficiently close to the attachment curve, they snap together at that point. In this case, a signal mast arm has been attached.

Creating Prop Attachment Curves

RoadRunner does not have a user interface for creating prop attachment curves directly. However, if you have access to a third-party tool like Maya® or Blender®, you can create these yourself on any prop. Add a spline named "attachment" into the object hierarchy.

If the attachment curve is not appearing in RoadRunner, you may need to add more curve points so that it can be detected. In Maya, this option is under Curve > Rebuild.

Format Details

FBX Details

  • Layered Textures are not supported and will not be connected to the imported materials.

  • Texture transformations (scale, rotation, and translation) are not supported and will be ignored.

  • RoadRunner supports importing FBX® Lambertian and Phong materials.

  • Multiple UV sets are not supported. These extra UVs must be removed in a program like Maya before being imported into RoadRunner.

  • Importing lights from FBX files is not supported.

  • Levels of Detail (LODs) are based on the node name. During import, RoadRunner checks if the node name ends with "_med", "_low", or "_verylow".


    RoadRunner does not render lower LODs, so nodes that end in "_med", "_low", or "_verylow" will not be visible.

glTF Details

  • Texture sampler settings are not imported and defaults to "repeat" on both axes.

  • Sparse accessors are not supported.

  • Point and line primitive modes are not supported.

OpenSceneGraph Details

  • When importing materials, osg::Textures are loaded as materials. These single texture materials will take precedence over osg::Materials when generating the mesh.

  • Only "Overall" and "Per Vertex" color bindings are supported.

  • Multiple UVs are not supported. Only the first texture coordinate array is used.

  • Point and line PrimitiveSet modes are not supported.

Advanced Details


Most 3D models have associated image files (such as texture maps or normal maps). Place these image files in the same directory as the prop model itself, or (in certain formats, such as FBX) they can also be embedded into the actual prop file.

Unit Scale and Coordinate System

  • RoadRunner uses meter units. Imported FBX files will automatically convert units if needed.

  • RoadRunner uses the Maya Z-up coordinate system: +Z is up, +X is right, and -Y is toward the camera.


    Imported FBX files will automatically rotate to match the coordinate system. However, FBX files created in a left-handed coordinate system will not be converted properly.