Setup a quadruped character

Skeleton

The first step is to set up the skeleton. The first step is to choose and set the pelvises. Atoms is able to apply the ground adaptation to any bones tagged as a pelvis. It will adapt the bone chain between the pelvises to match the ground slope.

Open the skeleton editor. Make sure to have the Asset detail panel visible. Otherwise open it from the Window->Asset Detail menu.

Add a new “Atoms Skeleton User Data” object to the asset user data slot.

Add the 2 pelvis bones. In the horse example inside the image. The pelvises are the “Pelvis“ and “Spline2“ bones. During the simulation Atoms adapts these two bones to keep the right ground height distance and it rotates the chain between these two bones to match the right slope.

Now add the 4 legs information needed by the Atoms ik solver.

The FootRoot is the root of the ik chain, the “Foot Ik” is the ik handle and the “Foot Tip” is the bone that rotates the toes.

The pole vector is a position in world space that define the pole vector position. If you leave a value of 0,0,0 Atoms try to compute one for you. Otherwise you can check the world location of the “Foot root“ bone and then add an offset, so the point is in front of your bones.

In the horse example this is the setup for the 4 legs.

Left leg:

• Foot Root: L-Calf

• Foot IK: L-Foot

• Foot Tip: L-Toe0

• Pole Vector: (X=15.293947,Y=10.000000,Z=81.905411)

Right leg:

• Foot Root: R-Calf

• Foot IK: R-Foot

• Foot Tip: R-Toe0

• Pole Vector: (X=-15.294092,Y=10.000000,Z=81.905495)

Front left leg:

• Foot Root: L-UpperArm

• Foot IK: L-Hand

• Foot Tip: L-Finger0

• Pole Vector: (X=13.898858,Y=105.624832,Z=94.751633)

Front right leg:

• Foot Root: R-UpperArm

• Foot IK: R-Hand

• Foot Tip: R-Finger0

• Pole Vector: (X=-13.898759,Y=105.624870,Z=94.751671)

Agent Variation

Create a new “Atoms Agent Variation” asset. Add the body and clothes skeletal meshes you want to use for this variation to the skeletal meshes array.

Agent Type

Create a new atoms agent type asset. Add to the skeleton slot the skeleton asset. then add the agent variation you created to the skin asset slot.

Animation sequences

Now that your agent type is ready and you set all the legs and pelvis information you can setup the animation sequences.

Animation clip (AtomsUnreal)