Rig conversion - Houdini

This workflow is now optional. The setup can be done directly from the Atoms UI. You don't need to process the asset anymore. If you are using Atoms 3.6.0 or a newer version, please go to the Building an Agent Type tutorial.

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.

Always export your character definition from the bind pose.

Preparing your scene

As explained in the Agent type page, our agent types will need a skeleton and skinned geos.
You should gather all your skinned meshes under one group. How you name these groups does not really matter as long as it makes sense to you.

There is no naming convention for your skinned geometry.

AtomsHoudini supports only rig made of null-bones objects for each joint. Usually this type of rig are used by the houdini fbx importer. Native houdini crowd rigs (made by bones only) are not supported by Atoms.

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 > Rig/Animation Exporter

The Skeleton Exporter GUI will pop up.

The "Root Joint" field must be set to the root joint of your skeleton, while the lists below are designed to tag, untag and list specific joints of your skeleton (pelvis and leg) as explained in the Agent type page).

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 houdini parameters on those joints. Please check the property panel after pressing these buttons to see which attributes are added.

The "Extra Joints" list is where you'll add your prop joints.

Each joint list has buttons for adding and removing joints from the lists, a sanity check button which will turn red if there's something wrong with your skeleton (you can click on it to have a report about what's wrong with your rig) and a help button which displays a help tooltip to let user know what each tag means.
Each list has a menu for selecting the joints and performing other actions.

The "Proxy" field will point to your proxy geos group. You can ignore this field, proxy geos are deprecated and will be removed in the next version of Atoms.

The "Skin" field will point to your skinned geos group.

Please use the "Config path" field to set your destination folder location.

Exporting your files

For this example we're going to work with the man.hip scene shipped with AtomsHoudini inside the AtomsHoudini/data folder. 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 "Pick from selection" button on the "Root Joint" line.
With the Hip joint selected, click on the "+" button under the "Pelvis Joints" list.
Select the LeftUpLeg and RightUpLeg joints and click on the "+" button under the "Foot Root Joints" list.
You can set the pole vector of the ik chain by moving the new null node that has just been created in the viewport. This must be a point in world space and you can find this parm in the Houdini property panel, by default Atoms tries to find a sensible value using the position of this foot root first child joint. For selecting the pole vector for each foot root you can right click to an element of the list and select the pole vector via the menu.
Select the LeftFoot and RightFoot joints and click on the "+" button under the "Foot IK Joints" list.
Select the LeftToeBase and RightToeBase and click on the "+" button under the "Foot Tip Joints" list.

Then:

Select the "Skin_GRP" null node and click on the "Pick from selection" button next to the "Skin" label. Click "Pick selection" on the popup menu.
Select a file path where to save your atomsskel file.

At this point the GUI should look like in the picture.

Click on Export and your files will be exported in the right location:

In this example we did not have any extra (prop) joint or chains detached from the root. 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