Wing Anatomy and Kinematics

CS137 Assignment #4

1. Dates

2. Goals

1.      Learn about the issue of representing animal anatomy in 3D

2.      Appreciate and learn to visually explain the complexity of the motion of a bat's wings.

3. Readings

·         Check the calendar page of the course's webpage for readings.

4. Assignment

4.1 Part A: Wing Structure Illustration

    Based on the readings, slides, the field trip and Sharon's lecture on the bone and muscle structure of a bat's wing, create an illustration of that anatomy in flight. You should create, in any media you prefer, a SINGLE FRAME of any stage of the wingbeat cycle that displays the interconnection of muscular action, the connection and bending of the bones, the flexing of membranes and suggests the movement of the wing through the surrounding air.

The primary focus of the assignment is anatomical structure. Simple flow issues should play a part in your thinking as you build your wing and show it in action, but complex aspects of the flow need not be indicated, unless there is particular phenomenon that you want to highlight.  The full interaction between form and flow will be the focus of our final project after Thanksgiving. This assignment concentrates on the Form that generates the Force. Study all elements involved in how the form moves and actuates and try to show all of those in a clear manner. You must make some decisions about which elements should dominate the composition and why, but try to relate your reasoning back to the science of bat flight.

If there is a part of the anatomy you would like to pay special attention to, especially if its role in the action seems vital to the flight capability of the bat, you might try to depict that part in greater detail. A fully naturalistic scapula, to name a particularly ambitious focus, could be drawn in the midst of an otherwise abstracted anatomical structure. You will need to support your choice of that particular piece and the function it plays in the kinematics of the bat, and specify the active anatomical connections between the piece you are working on and the rest of the wing's structure.

OPTION 1: It is possible to approach this assignment through fully realized naturalistic form, but this may prove to be too time-consuming. Experiment with abstract depiction as a labor saving strategy, and also as a way of showing stress, contraction of muscle, bone flexion etc.  For example, bones can be drawn as simple lines rather than elaborately modeled forms, but might also be color coded to suggest reaction to force generated by muscle or air pressure. An abstract approach will most likely be necessary in dealing with the wing membranes, which are broad, complex surfaces difficult to describe with CavePainting strokes. In this case, a mesh, grid, or pattern may be a better choice to describe the wing surface, and could contain a gradient suggesting varying forces.

OPTION 2: This said, anatomical illustration clarified to the point where we understand muscle and tendon attachments, active versus inactive muscles, bone articulations and structure, etc. is actually really valuable to Sharon. Take this assignment as an opportunity to explore that level of illustration for a very specific part of the bat's anatomy. Pick the right frame to work in for showing something interesting.  If you want to show a bone really bending, pick a frame where it's really bending, not one where it's inactive, etc. Taking this more realistic route can setup RISD students who are interested in anatomical illustration for understanding how that might play a part in a final project, and it will give Brown students a sense of why that is valuable and how it is done.

As with all assignments to date, legibility is a key factor. Sketch on paper or in the Cave, both ahead of time and during the execution phase to test ideas and visual relationships.

4.2 Part B: Wing Stroke Sequence

    Translate your design into CavePainting. You should concentrate on making sure all the key elements of the bat's body that you need are visualized in all frames, but highlight the ones you think are acting at each step in the wing beat. Your animation should make clear what parts of the wing are doing what at each point in time.

4.3 Other tasks

As part of each assignment, there will be a few questions that you should answer.  These can be found at the end of this handout and your answers should be emailed to the TAs (cs137tas@cs.brown.edu) by 9 AM (an hour before class starts) on Monday 11/6.  Most of these are very short questions intended to help guide you through the assignment.  They should not take long to answer.  Most of the time, a very brief, one sentence or less, answer is sufficient.

5. Questions (answer briefly)