Your characters must be exported into Atoms Crowd format files before you can use them in your simulations. In this section we are going to see how you can do it.
Some guidelines will also be given on how you should layout your scene to be exported correctly.
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Always export your character definition from the bind pose. |
Preparing your scene
As explained in the Agent type page, your agent types will need a skeleton, some proxy and skinned geos.
You should gather all your proxy meshes under one group and your skinned meshes under another group. How you name these groups does not really matter as long as it makes sense to you.
The only naming convention applies to the proxy geometries. Atoms Crowd will try to match each joint with a mesh under the proxy geometry group, the mesh name must be equal to the joint name followed by "_GEO".
For instance, if you have a joint named "Hips", the proxy GEO associated with that joint should be named "Hips_GEO".
There is no naming convention for your skinned geometry.
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Make sure your joint local rotation values are always set to 0 before exporting your rig. |
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Atoms viewport skinning preview only supports 3 joint weights per vertex maximum. Please make sure to skin each vertex to 3 joints maximum or the Viewport preview won't display correctly. |
Opening the Skeleton Exporter Tool
Once your scene is ready, you can open the skeleton and animation exporter tool using the shelf button. You can also open it via the Atoms menu: Atoms > Export > Skeleton/Animation Exporter
The Skeleton Exporter GUI will pop up.
You'll notice some buttons at the top of the UI. They are used to tag or untag the selected skeleton joints (pelvis and leg) as explained in the Agent type page. You can also use them to select all the joints with the given tag.
Atoms need to know this information in order to place correctly your agent on the ground, apply the IK and the foot lock during the simulation.
Tagging just means adding some maya attributes (or houdini parameters) on those joints. Please check the attribute editor (or property panel) after pressing these buttons to see which attributes are added.
The "Root Joint" field must be set to the root joint of your skeleton.
The "Extra Joints" list is where you'll add your prop joints.
The "set bind pose attributes" button takes care of setting the bind pose attributes on each joint of your hierarchy. You should press this button before exporting and saving your scene.
Whenever you tweak you rig (i.e. move or rotate a joint) you should press this button again in order to set again all the right bind pose data.
The "Geos" field will point to your proxy geos group.
The "Skin" field will point to your skinned geos group.
Please use the "Config path" field to set your destination folder location.
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Exporting your files
For this example we're going to work with the AtomsRobot.ma scene shipped with Atoms. In this scene all the joints and geos are already prepped correctly.
First let's tag our joints:
- Select the Hip joint and click on the "Pelvis" button, then "tag".
- Select the LeftUpLeg and RightUpLeg joints and click the "Foot Root" button, then "tag".
You can set the pole vector of the ik chain by moving the new annotation node that has just been created in the viewport. This must be a point in world space and you can find this attribute inside the Extra Attributes section for this foot root, by default Atoms tries to find a sensible value using the position of this foot root first child joint. - Select the LeftFoot and RightFoot joints and click the "Foot IK" button, then "tag".
- Select the LeftToeBase and RightToeBase and click the "Foot Tip" button, then "tag".
Then:
- Select the Hip joint again and click on the "Refresh" button next to the "Root Joint" label.
- Click on the "set bind pose attributes" button
- Select on "RobotGeo" group and click on the "Refresh" button next to the "Geos" label.
- Select on "RobotSkin1" group and click on the "Refresh" button next to the "Skin" label.
- Select a file path where to save your atomsskel file.
At this point the GUI should look like in the picture.
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| The pole vector is used when atoms apply the IK system on the legs when the agent is on a ground. It's better to setup a pole vector in order to have a better simulation. If you don't set a pole vector atoms will try to estimate one from the joint configuration. |
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You can also tag joints with the "Skip IK" button. This will instruct Atoms not to use those joints as part of the IK chain when rebuilding the leg. |
Click on Export and your files will be exported in the right location:
In this example we did not have any extra (prop) joint. In case you do just select them and click on the plus button before clicking the "set bind pose attributes" button.
Add custom data
If you want add some custom data to some joints please check the Adding custom metadata section