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222 lines
8.3 KiB
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222 lines
8.3 KiB
ReStructuredText
########################
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Static Model via COLLADA
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########################
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This tutorial shows how to get a static model from Blender to OpenMW
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using the COLLADA format. It does not cover using Blender itself, as there are
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many better resources for that. The focus is solely on the pipeline and its
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specific requirements. Static models are those that don’t have any animations
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included in the exported file.
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Requirements
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************
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To use the Blender to OpenMW pipeline via COLLADA, you will need the following.
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* `OpenMW 0.47 <https://openmw.org/downloads/>`_ or later
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* `Blender 2.83 <https://www.blender.org/download/>`_ or later. Latest confirmed, working version is Blender 3.0
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* `OpenMW COLLADA Exporter <https://github.com/openmw/collada-exporter>`_
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* A model you would like to export. In our case, it's a barrel.
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The Barrel
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**********
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The barrel shown in this tutorial, and its revelant files, are available from
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the `Example Suite repository <https://gitlab.com/OpenMW/example-suite/-/tree/master/example_static_props>`_.
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This should be useful for further study of how to set up a static prop in case
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the tutorial is not clear on any particular thing.
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.. image:: https://gitlab.com/OpenMW/openmw-docs/-/raw/master/docs/source/reference/modding/custom-models/_static/barrel-prop-in-blender.webp
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:align: center
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* ``data/meshes/the_barrel.dae`` – exported model
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* ``data/textures/the_barrel.dds`` – diffuse texture
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* ``data/textures/the_barrel_n.dds`` – normal map
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* ``data/textures/the_barrel_spec.dds`` – specular map
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* ``source_assets/the_barrel.blend`` – source file configured as this tutorial specifies
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Location, Rotation, Scale
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*************************
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First, let's take a look at how the fundamental properties of a scene
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in Blender translate to a COLLADA model suitable for use in OpenMW. These apply
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the same to static and animated models.
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Location
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========
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Objects keep their visual location and origin they had in the original scene.
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Rotation
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========
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* Blender’s +Z axis is up axis in OpenMW
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* Blender’s +Y axis is front axis in OpenMW
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* Blender’s X axis is left-right axis in OpenMW
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Scale
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=====
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Scale ratio between Blender and OpenMW is 70 to 1. This means 70 units in
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Blender translate to 1 m in OpenMW.
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However, a scale factor like this is impractical to work with. A better
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approach is to work with a scale of 1 Blender unit = 1 m and apply the 70 scale
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factor at export. The exporter will automatically scale all object, mesh,
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armature and animation data.
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Materials
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*********
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OpenMW uses the classic, specular material setup and currently doesn't support
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the more mainstream `PBR <https://en.wikipedia.org/wiki/Physically_based_rendering>`_ way.
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The COLLADA exporter takes values from ``Specular BSDF`` node of the material
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assigned to the mesh. In case no node or material is assigned, a default white
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material is exported. The following list presents material values in the
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exported COLLADA file and what value in Blender affect them.
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Diffuse
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=======
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Diffuse value is taken from ``Base Color`` of the Specular BSDF node. To get
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visually matching results between Blender and OpenMW, set Blender's Color
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Management ``Display Device`` to ``None``.
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Specular
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========
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Specular value is taken from ``Specular`` of the Specular BSDF node.
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Ambient
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=======
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Ambient value is taken from the ``World Background Color`` of Blender's
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currently active world. The value is found in the ``World Properties`` tab,
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``Surface panel``, when the world is not using nodes.
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Emission
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========
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Emission value is taken from ``Emissive Color`` of the Specular BSDF node.
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Double-sided
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============
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This is controlled by the ``Backface Culling`` toggle found under material
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options. When Backface culling is enabled, the material will be exported as
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single-sided.
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Shininess
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=========
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Shininess value is taken from ``Roughness`` of the Specular BSDF node. Shininess
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and Roughness refer to the same material property but use an opposite scale. The
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higher the roughness, the lower the shininess.
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Transparency (alpha blend)
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==========================
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Blend transparency is used when ``Blend Mode`` of the material in Blender is set
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to ``Alpha Blend``. The setting is found under material options. Amount of
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transparency is then controlled by ``Transparency`` of the Specular BSDF node.
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Transparency (alpha clip)
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=========================
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Alpha clip transparency is used when ``Blend Mode`` of the material in Blender
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is set to ``Alpha Clip``. In OpenMW, transparency values are taken from the
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alpha channel of the diffuse texture. When previewing diffuse texture's alpha
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channel, be mindful that Blender uses an inverted scale for transparency
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compared to OpenMW.
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Textures
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********
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For textures, a diffuse texture needs to be connected to the ``Base Color``
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socket of the Specular BSDF node. This is enough for the material to be included
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in the exported COLLADA file.
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.. image:: https://gitlab.com/OpenMW/openmw-docs/-/raw/master/docs/source/reference/modding/custom-models/_static/barrel-prop-in-blender-material.webp
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:align: center
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Additional texture types, such as specular or normal maps, are used
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when enabled in the OpenMW Launcher with the ``Auto use object normal maps``
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and ``Auto use object specular maps`` options. The textures need to follow the
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name of the diffuse texture with an additional suffix, and be in the same
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folder. OpenMW will then automatically recognize and use these textures. In the
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case of the barrel, the textures are named:
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* ``the_barrel.dds`` - diffuse texture
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* ``the_barrel_n.dds`` - normal map
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* ``the_barrel_spec.dds`` - specular map
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Texture Paths
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=============
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Textures will show properly in OpenMW when the path in the exported COLLADA file
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is as follows ``textures/the_barrel.dds``. The exporter detects the
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``data/textures`` part of the texture's path in Blender and truncates the rest.
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The texture path can also be set manually in the exported COLLADA file.
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Textures Not Visible
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====================
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If a texture doesn't show on the exported model in OpenMW-CS or in-game, it's likely
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the file path to the texture is incorrect and OpenMW can't find it.
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To fix this you can open the exported ``.dae`` file in a text editor and check
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the texture's filepath. In the example of this barrel model it's found on lines 13-17.
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.. code::
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<library_images>
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<image id="id-image-4" name="the_barrel">
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<init_from>textures/the_barrel.dds</init_from>
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</image>
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</library_images>
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A path to a texture must always start with ``textures/`` and then continues with
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whatever subfolders the texture is in. It's a common issue that the path can start
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with ``../textures/`` in which case you can manually remove the ``../``
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and the textures should then show.
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Collision Shapes
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****************
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In Blender, a custom collision shape is set up with an empty named
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``Collision`` or ``collision``. Any mesh that is a child of this empty will be
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used for physics collision and will not be visible in-game. There can be
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multiple child meshes under ``collision`` and they will all contribute to the
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collision shapes. The meshes themselves can have an arbitrary name, it's only
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the name of the empty that is important. The ``tcb`` command in OpenMW's in-game
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console will make the collision shapes visible and you will be able to inspect
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them.
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.. image:: https://gitlab.com/OpenMW/openmw-docs/-/raw/master/docs/source/reference/modding/custom-models/_static/barrel-prop-in-blender-collision.webp
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:align: center
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If no custom collision shape is present, OpenMW will use the regular
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mesh itself, which is not optimal and should be avoided.
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Exporter Settings
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*****************
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For static models, use the following exporter settings. Before export, select
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all objects you wish to include in the exported file and have the "Selected
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Objects" option enabled. Without this, the exporter could fail.
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.. image:: https://gitlab.com/OpenMW/openmw-docs/-/raw/master/docs/source/reference/modding/custom-models/_static/dae-exporter-static.webp
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:align: center
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Getting the Model in-game
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*************************
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Once the model is exported, it needs to be placed in the correct folder where
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OpenMW will read it. In OpenMW-CS it can then be assigned to an object and added
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to a world cell.
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.. image:: https://gitlab.com/OpenMW/openmw-docs/-/raw/master/docs/source/reference/modding/custom-models/_static/barrel-prop-in-openmwcs.webp
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:align: center
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