A Hinge Connection at the character’s elbow.

A Hinge Connection links two rig elements and limits their rotation by confining it to a singular plane. The plane itself is defined by the positions of the Point Controllers used to create a hinge.

In a Cascadeur rig, Hinge Connections should be created for parts that are supposed to only bend across a single axis. For a humanoid character, these are:

• Elbows
• Knees
• Toes

Creating Hinges

To create a hinge connection:

1. Create rig elements for both Joints that should be connected by a hinge.

2. Select these rig elements.

3. On the Hinge actions panel, click the Union to hinge button:

4. This will place the Additional Points attached to the rig elements in the same place:

When the actual rig is generated, Cascadeur will interpret this as a marker for a hinge connection and create a hinge there.

Cascadeur can also automatically create a Direction Controller for the hinge.
This is only possible if the hinge is orthogonal to the edge that connects the Main controller with the Main Direction controller.

If the hinge is not orthogonal to the limb, you can fix this by using the Ortho hinge function:

1. Select both of the hinge controllers.

2. Click the Ortho hinge button:

Ortho hinge moves the Additional Point to the point on which the hinge is placed.

Straighten to hinge does the opposite: moves the hinge point (and the rig element to which it is attached) to the Additional Point:

This function can be used in situations when the Direction Controllers are generated with the wrong directions (because of how limb Joints are placed, for example).
To fix this, you can move Additional Points, and then use Straighten to hinge to change the hinge’s position - and with it, how the Direction Controllers are oriented.

Hinge Settings

Create direction controller
If this is enabled, the software will add a Direction Controller to the hinge when the rig is generated.

Direction controller is right
If this is enabled, the Direction Controller’s spatial orientation will be flipped when the rig is finalized. Can be used when you need to change the controller’s direction.
Disabled by default.

Direction controller length
Sets the length for the edge of the Direction Controller.
The default value is 50.

Is additional
This parameter should be enabled when you create a second Hinge connection in a row (i.e. when the previous prototype already has a Hinge connection). 
Disabled by default.

Direction Controllers

When you create a hinge connection, you also want to create a direction controller for it so you could adjust the orientation of the hinge.

To create it:

1. Select the second rig element associated with the limb for which you create a hinge.

2. In the Outliner window, open the Hinge settings tab.

3. On this tab, enable Create direction controller:

4. Now when you create a hinge connection for this joint, the program will generate a direction controller for it.

Keep in mind, however, that Direction Controllers are only required when you need an option to change the limb's direction.
When you don't need such an option option - which is often the case for short body parts such as toes in humanoid models - you can leave this setting disabled.

Hinge connections at knees (left) and at toes (right); as you can see, toe hinges do not have Direction Controllers.

Double Hinge Connections

Sometimes, the structure of the limb would imply several Hinge Connections in succession.

The Sabertooth model from the standard Cascadeur package includes such a setup.

For a case like this:

1. Select the rig elements for the next part of the limb.

2. Open the Hinge settings tab in the Object Properties panel.

3. Enable the Is additional option:

Important note:
Make sure that the Additional Points are on the same side as the ones in the preceding hinge connection.

It is recommended to place Additional Point not only on the same side, but so it would be perpendicular to the bending axis of the hinge connection.

To do this:

1. Select one of the hinge’s Additional Points.

2. Set pivot to the knee.
To do this, right-click the knee Point and select Set pivot from the menu.

3. Set parameters in the Scene Settings → Copier:
Mode should be set to Global.
Relative should be enabled.

4. Use Edit → Copy to copy the Additional Point’s position.

5. Select the next Additional Point.

6. Set its pivot to foot

7. Use Edit → Paste to apply the copied position to it.