Articulated wings, animating a bird's wings copyright of Giulio Porta 2005, all rights reserved.

This tutorial will take you through the fundamental approaches of modeling and animating a mechanical bird.

The technique that we are going to use is known as Forward Kinematics, this technique along with Inverse Kinematics is used to articulate and animate segmented models, in other words models made out of more then one piece.

On the contrary model made out of one piece can be articulated with a rig, a skeletal system based on a technology known as bones. We'll deal with bones in a separate tutorial.

In the previous tutorial, the bird's wing were each made out of one piece, in this new tutorial we'll model each wing in 3 pieces so they can articulate and animate closer to what a bird's wings do in real life.

A bird's wing is articulated by several major components in a remarkably similar manner to that of a human arm.
We are going to to simplify the bird's wing complex articulation into 3 parts like the one of the Albatross.

Because it maybe difficult to perceive the effect that these complex articulations may have in the bending of the wing, 3 articulations will be enough to simulate the kind of bend the a bird's wing maybe subjected to in flight, or in lifting the bird off ground.

Segmented models and Forward Kinematics

We are going to build a segmented model. Segmented just like the bones of the human body. This bird's wings will be made out of 3 pieces and it will represent an approximation of a real wing.

Segmented models can be animated by using concepts such as Forward Kinematics or Inverse Kinematics.

With Forward Kinematics segmented objects are linked to each other beginning from the their extremities (in the case of a bird from the tip of its wings, for a human the fingers) all the way to the core of the object, usually the pelvis. Forward Kinematics works well for animating mechanical objects, in our case the pieces of the bird's wing.

Drawing the wing's 3 pieces

With the Add Polyline tool draw the 3 pieces that the wing will be made out of.

Make sure that the shapes are closed, click on the Close Shape icon in the context tool panel before you actually close the shape like you would do in programs like Illustrator of Photoshop. In other words do not connect the first and last points of your shape, stop before you do that and click on the Close Shape icon instead.

 

Even though your shape may look like polygons they are in reality NURBS, curves masqueraded as straight lines.

Click on the Convert NURBS icon

Notice that your shape will acquire a solid look, NURBS are hollow and they cannot be extruded with the same tools as polygons.
Select each win's component and Sweep it to give it some thickness.
Add an edge down the center of each of the components.

You could do this above and below each portion of the wing

Relocating axis

Select the outer part of the wing

Look for the Axis icon and click on it, that will activate the object axis. You should see the x,y,z tripod active.

Move the axis to the pivot or hinge point were that portion of the wing will rotate.

Turn the Axis off by clicking on the Axis icon.

In a Side View, as you can see here to the right, with the axis turned off, R + click and drag to see how well that portion of the wing rotates.

Forward kinematics

Now that the axis of the outermost portion of the wing has been selected, and relocated to its pivot point, we can begin with the Forward kinematics process of "gluing" the segments of the wing together. here are the steps you'll need to take:

  • Use the Glue as a Child tool and "glue" the the first tip of the wing to the second one.
  • Activate the Axis of these two pieces of the wing that have been glued together and move it to the pivot point of the secong piece of the wing.
  • Use the Glue as a Child tool and "glue" the the first and second piece of the wing to the third piece.
  • Activate the Axis of these three pieces of the wing  and move it to the pivot point of the third piece of the wing.

Notice that because of the particular hierarchy that we have created among the the wing's components, their axis's sizes ranges from a smaller size to a larger size at the end of  wing's hierarchy.

Once you are finish setting up one wing copy it Ctrl + C and use the Mirror tool to flip the copy.

Once the wing is copied and mirror along its axis, it will have to be moved away from the other wing to allow room for the bird's body.