Static Model via COLLADA

This tutorial shows how to get a static model from Blender to OpenMW using the COLLADA format. It does not cover using Blender itself, as there are many better resources for that. The focus is solely on the pipeline and its specific requirements. Static models are those that don’t have any animations included in the exported file.

Requirements

To use the Blender to OpenMW pipeline via COLLADA, you will need the following.

• OpenMW 0.47 or later
• Blender 2.83 or later. Latest confirmed, working version is Blender 3.0
• OpenMW COLLADA Exporter
• A model you would like to export. In our case, it’s a barrel.

The Barrel

The barrel shown in this tutorial, and its revelant files, are available from the Example Suite repository. This should be useful for further study of how to set up a static prop in case the tutorial is not clear on any particular thing.

• data/meshes/the_barrel.dae – exported model
• data/textures/the_barrel.dds – diffuse texture
• data/textures/the_barrel_n.dds – normal map
• data/textures/the_barrel_n.dds – specular map
• source_assets/the_barrel.blend – source file configured as this tutorial specifies

Location, Rotation, Scale

First, let’s take a look at how the fundamental properties of a scene in Blender translate to a COLLADA model suitable for use in OpenMW. These apply the same to static and animated models.

Location

Objects keep their visual location and origin they had in the original scene.

Rotation

• Blender’s +Z axis is up axis in OpenMW
• Blender’s +Y axis is front axis in OpenMW
• Blender’s X axis is left-right axis in OpenMW

Scale

Scale ratio between Blender and OpenMW is 70 to 1. This means 70 units in Blender translate to 1 m in OpenMW.

However, a scale factor like this is impractical to work with. A better approach is to work with a scale of 1 Blender unit = 1 m and apply the 70 scale factor at export. The exporter will automatically scale all object, mesh, armature and animation data.

Materials

OpenMW uses the classic, specular material setup and currently doesn’t support the more mainstream PBR way. In Blender, the mesh needs a default material with a diffuse texture connected to the Base Color socket. This is enough for the material to be included in the exported COLLADA file.

Additional texture types, such as specular or normal maps, are used when enabled in the OpenMW Launcher with the Auto use object normal maps and Auto use object specular maps options. The textures need to follow the name of the diffuse texture with an additional suffix, and be in the same folder. OpenMW will then automatically recognize and use these textures. In the case of the barrel, the textures are named:

• the_barrel.dds - diffuse texture
• the_barrel_n.dds - normal map
• the_barrel_spec.dds - specular map

Collision Shapes

In Blender, a custom collision shape is set up with an empty named Collision or collision. Any mesh that is a child of this empty will be used for physics collision and will not be visible in-game. There can be multiple child meshes under collision and they will all contribute to the collision shapes. The meshes themselves can have an arbitrary name, it’s only the name of the empty that is important. The tcb command in OpenMW’s in-game console will make the collision shapes visible and you will be able to inspect them.

If no custom collision shape is present, OpenMW will use the regular mesh itself, which is not optimal and should be avoided.

Exporter Settings

For static models, use the following exporter settings. Before export, select all objects you wish to include in the exported file and have the “Selected Objects” option enabled. Without this, the exporter could fail.

Getting the Model in-game

Once the model is exported, it needs to be placed in the correct folder where OpenMW will read it. In OpenMW-CS it can then be assigned to an object and added to a world cell.