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225 lines
8.6 KiB
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#############################
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Animated Creature via COLLADA
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#############################
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This tutorial shows how to get an animated creature from Blender to OpenMW using
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the COLLADA format. It does not cover using Blender itself, as there are many
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better resources for that. The focus is solely on the animation pipeline and its
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specific requirements. Most of them are related to how the model, rig, and
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animations are set up in Blender.
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.. note::
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This tutorial builds upon the :doc:`pipeline-blender-collada-static-models` tutorial. All fundamentals of exporting static objects apply to animated ones as well.
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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 0.48 <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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* An animated model you would like to export. In our case the flamboyant Land Racer!
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The Land Racer
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**************
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The creature, and its revelant files, are available from the `Example Suite repository <https://gitlab.com/OpenMW/example-suite/-/tree/master/example_animated_creature>`_.
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This should be useful for further study of how to set things up in case this
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tutorial is not clear on any particular thing.
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* ``data/meshes/land_racer.dae`` – exported model
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* ``data/meshes/land_racer.txt`` – animation textkeys
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* ``data/textures/land_racer.dds`` – diffuse texture
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* ``data/textures/land_racer_n.dds`` - normal map
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* ``source_assets/land_racer.blend`` – source file configured as this tutorial specifies
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Model
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*****
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The model needs to be a child of the rig and have an Armature modifier asigned.
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Bone weights are limited to a maximum of 4 bones per vertex. The model needs to
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have default location, rotation, and scale.
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.. image:: https://gitlab.com/OpenMW/openmw-docs/-/raw/master/docs/source/reference/modding/custom-models/_static/landracer-in-blender.jpg
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:align: center
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Collision Shape
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***************
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Collision is set up with an empty named ``Collision`` or ``collision`` with a
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single child mesh. OpenMW will use the bounding box of this mesh for physics
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collision shape so a simple, cuboid mesh is enough. If no collision shape is
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defined, the bounding box of the animated model will be used instead.
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.. image:: https://gitlab.com/OpenMW/openmw-docs/-/raw/master/docs/source/reference/modding/custom-models/_static/landracer-collision-shape.jpg
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:align: center
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Armature / Rig
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**************
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.. note::
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Only a single rig object should be included in the exported file. Exporting multiple rigs is not reliably supported and can lead to errors.
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Root
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====
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The rig needs to be structured in a specific way. There should be a single top
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bone in the rig’s hierarchy, the root bone named ``Bip01``. The name is
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required so OpenMW recognizes and uses it for root movement. For this same
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reason, the bone should be by default aligned with the world. The root bone
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needs to have its ``Deform`` flag **enabled**.
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.. image:: https://gitlab.com/OpenMW/openmw-docs/-/raw/master/docs/source/reference/modding/custom-models/_static/landracer-root-bone.jpg
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:align: center
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Deform Bones
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============
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Below the root bone, the bones are divided into two branches. One branch
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contains the deform bones which get included in the final exported file. These
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are otherwise not animated directly but inherit motion from other bones via
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constraints. They have their ``Deform`` flag **enabled**. For creatures, the
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deform bones can be named as you desire and don’t need to follow the naming
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convention used for NPC and player models.
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.. image:: https://gitlab.com/OpenMW/openmw-docs/-/raw/master/docs/source/reference/modding/custom-models/_static/landracer-rig-hierarchy.jpg
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:align: center
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Control Bones
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=============
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The other branch holds control and helper bones that enable comfortable
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animation in Blender, but are neither required nor included in the exported
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file. They have their ``Deform`` flag **disabled**. How these bones are
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structured is a big separate topic on its own that this tutorial does not cover,
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but you can study the provided source file.
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Animations
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**********
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A creature in OpenMW is expected to have a set of animations to display its
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various actions. These animations are recognized and used by their name.
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.. list-table::
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:widths: 25 25 50
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:header-rows: 1
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* - Animation name
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- Possible variations
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- Purpose
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* - attack1
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- attack2, attack3
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- The creature performs an attack
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* - death1
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- death2 - death5
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- The creature dies while upright
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* - hit1
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- hit2 - hit5
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- The creature is hit in combat
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* - idle
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- idle2 - idle9
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- Flavour animations when the creature does nothing in particular
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* - knockout
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- /
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- When creature's fatigue goes below 0 and it staggers to the ground
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* - deathknockout
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- /
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- The creature dies while knocked out
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* - knockdown
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- /
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- When the creatures receives a heavy hit in combat or lands from a considerable height
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* - deathknockdown
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- /
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- The creature dies while knocked down
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* - runforward
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- /
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- Moving forward fast
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* - walkforward
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- /
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- Moving forward at regular speed
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Animating in Blender is done at 30 fps. Specific to how OpenMW works, each
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exported animation needs to take a unique range on the timeline. To achieve
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this, actions are placed as strips in the NLA editor with an obligatory one
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frame gap between them.
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.. image:: https://gitlab.com/OpenMW/openmw-docs/-/raw/master/docs/source/reference/modding/custom-models/_static/landracer-nla-strips.jpg
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:align: center
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NLA strips affect the exported result based on their scale, name, frame range,
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repetition, or any other factor affecting the end animation result. It's
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*What you see is what you get* principle.
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Root movement is required for animations such as ``walkforward`` and
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``runforward`` and is likely to work for other animations if needed.
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Root movement works only when the root bone is named ``Bip01``.
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Textkeys
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********
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The exported COLLADA file requires a corresponding textkeys file for OpenMW to
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properly read the animations. Textkeys is a ``.txt`` file containing animation
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definitions and events. At a minimum it needs to include at least animation
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``start`` and ``stop`` values in a format as shown in this example.
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.. code::
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idle: start 0.033333
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idle: stop 2.033333
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walkforward: start 2.066667
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walkforward: stop 3.666667
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runforward: start 3.7
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runforward: stop 4.433333
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attack1: start 4.466667
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attack1: stop 5.433333
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...
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The textkeys file is placed in the same folder as the model and matches the model's name.
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* ``meshes/land_racer.dae``
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* ``meshes/land_racer.txt``
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While it's possible to write textkeys by hand, OpenMW's COLLADA Exporter offers
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a convenient option to export them based on Blender's pose markers. **Pose markers
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are stored per action** and shouldn't be be confused with timeline markers which
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are global to the Blender file. When actions are present in the NLA Editor as
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strips, their containing pose markers will be used to write the textkeys. Any
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frame offset and scaling of the strips is taken into account and affects the
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final textkey values. Be sure to have ``Export Textkeys`` option enabled in
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the exporter.
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.. image:: https://gitlab.com/OpenMW/openmw-docs/-/raw/master/docs/source/reference/modding/custom-models/_static/landracer-textkey-markers.jpg
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:align: center
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In the example of ``attack1`` action, it needs to contain pose markers named
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``attack1: start`` at **frame 1** and ``attack1: stop`` at **frame 30**.
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Exporter Settings
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*****************
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For animated 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/landracer-exporter-settings.jpg
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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 Land Racer is exported, both of its ``.dae`` and ``.txt`` files need to
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be placed in the correct folder where OpenMW will read it. Afterwards in
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OpenMW-CS, it should be visible in the Assets->Meshes table and can be assigned
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to the ``Model/Animation`` field of a creature.
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.. image:: https://gitlab.com/OpenMW/openmw-docs/-/raw/master/docs/source/reference/modding/custom-models/_static/landracer-in-openmwcs.jpg
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:align: center
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