Description
1. Overview
This programming assignment is meant to acquaint you with 3D modeling and model transformation. You will
implement a creature model and make it move by performing transformations on its joints. You will also need to
submit a simple reference image or concept drawing and a screenshot of your model with your code.
Basic Requirements
Before coding, please have a look at the Component class defined in “Component.py”. We recommend calling
functions of the Component class in your keyboard event functions to make the joints/body of your creature move.
After reading the code in the “Component.py” file, you should start implementing features in the following blocks/files
in the skeleton code:
1. TODO 1 in “Component.py”: complete the Component.update() function that sets the transformation matrix of
each component. Most of this function has already been written: you only need to provide one line of code
that shows the correct multiplication order of the matrices that have already been created for you. Specifically,
you need to account for translations, rotations, and scaling. You can multiply numpy matrices together using
the @ operator (e.g. self.transformationMat = C @ B @ A).
Here is what the program will look like once the correct transformations are applied:
2. TODO 2 in “ModelLinkage.py”: implement your own creature class by following the form of the provided
ModelLinkage class. You will need to make use of the geometric primitives defined in Shapes.py. Combine
these shapes in a hierarchical fashion to construct a sufficiently complex 3D model of a creature (insect,
spider, scorpion, etc.) Please see “Model Requirements” for additional details on what is required of your
model. You will need to figure out how to store components in a hierarchical structure and set them in proper
position by chaining transformations. It is helpful to modularize your design in one class — you may wish to
reuse your model in future programming assignments.
3. TODO 3 in “Sketch.py”: After building your model, you need to create an instance of it in Sketch.py. See the
InitGL function.
4. TODO 4 in “Sketch.py” or “ModelLinkage.py”: Set up the joint behaviors of your creature. Please refer to the
Component class to see what functions are already available to you. Limit the angles at each joint within
reasonable ranges so that the creature’s legs, neck, head and any other parts don’t intersect or bend in
unnatural ways. The orientation of joint rotations for the left and right limbs must mirror each other.
5. TODO 5 in “Sketch.py”: Set up the keyboard events that make your creature act in different ways (change
poses, rotate limbs, etc.). Add a multi-select feature to the interface that allows you to control several
joints at the same time. You will need to set up at least 5 different poses for your creature as test cases.
Please check your keyboard events and test cases to see if they work as expected and satisfy our
requirements. See “Multi-Select Requirements” below for additional details.
6. TODO 6 in “Sketch.py” (CS680 required, CS480 Extra Credit): Implement an eye that always looks at the
position of the mouse. An eye should consist of a movable pupil and still sclera. The eye rotation only needs
to work correctly when the creature is looking toward the viewer — you do not need to account for other
camera orientations.
Extra Credit
7. Use a single quaternion transformation rather than a series of Euler rotations to implement the eye
tracking feature for additional credit.
Multi-Select Requirements
Your multi-select interface should behave as follows:
● Any subset of your model’s Components can be selected. When inducing a rotational change via the up/down
arrow keys or scroll wheel/trackpad, the rotation will be applied to all Components that are currently selected.
● Any individual Component can be added to the current selection or removed from the current selection
without adding/removing other Components.
● Selected Components are indicated visually to the user by setting their color to that of the current rotational
axis. This matches the behavior of the single-select interface that is provided to you.
● Once deselected, Components regain their original color.
The rest of the implementation is left up to you! One straightforward approach is to assign each Component of your
model to a key (you can use 1 through 0 and/or A through L for this purpose, since they don’t conflict with any other
program controls). When a Component’s assigned key is pressed, that Component is added/removed from the
current selection.
Model Requirements
In addition to roughly following the reference image/drawing you will provide, your model should be suitably complex:
● at least 6 limbs required (tails and wings count)
● at least one limb must have at least 3 joints
● at least two colors should be used
● at least two shape types must be used
● a pair of opposing limbs must be present (to test mirrored motions)
Programming Style
8. For any modified or newly added source file, you should include a brief description of how this file was
changed. Add this information to the file heading along with your name and ID. Your code should be readable
with sufficient comments. You should use consistent variable naming and keep reasonable indentation. You
may add helper functions to improve efficiency and readability.
README
With each assignment, please upload a README text or markdown file with the following information:
● your name
● any collaborators that you spoke to
● the class
● the assignment number
● a brief summary of the code and implementations you have written for the assignment
For the last point, you should outline the method you used to solve the problem, describe the variables and data
structures used in the program, any error conditions that might be encountered in the solution, and how these error
conditions are handled by the solution. This is a general description of your work, detailed comments are still
required in the code.
If these details are described in the comments above the relevant functions or files, you may be brief here. You may
call this file “README_Student” or something analogous to differentiate it from the README in the skeleton code.
Please include a mention of any resources that you consulted while completing your assignment.
2 Resources
2.1 Starter code
A Python Program skeleton, which includes basic classes, methods, and main pipeline, is provided for you. You are
expected to complete the sketch program by completing/modifying Sketch.py. There are comments in the skeleton
code that will help guide you in writing your subroutines. Some of them are noted as “TODO” or “BONUS” which
suggests you should complete the corresponding block.
The source files can be downloaded under the “Resources” tab on Piazza as “PA2 starter code.”
2.2 Environment setup
Installing the appropriate programming environment should be covered in a lab session. For more step-by-step
instructions, please refer to “Environment Setup” under the Piazza “Resources” tab.
2.3 User Interface
The user interface to the program is provided through mouse buttons and keyboard keys:
● ENTER/RETURN: Cycle through components
● LEFT-ARROW, RIGHT-ARROW: Iterate through different rotation axis for the currently selected component
● UP-ARROW, mouse SCROLL-UP: Increase selected component’s rotation angle along the selected axis
● DOWN-ARROW, mouse SCROLL-DOWN: Decrease selected component’s rotation angle along the selected
axis
● mouse Left-Drag: change the viewing angle
● mouse Right-Drag, mouse Middle-Drag: move the camera up/down and left/right
● r: reset the viewing angle
● R: reset everything in the scene
After modifications, your interface may be different from the example program provided here.
Don’t forget to ADD a multi-select feature so multiple joints can be changed simultaneously.
2.4 Demo
A video demo has been prepared to help you better understand your tasks and speed up your debugging process:
PA2_Demo.mp4
The following additional demo showcases the multi-select functionality & mirrored limb rotation:
3. Submission: Due Tuesday 10/14, 11:59 PM EST(midnight)
3.1 Files to Submit
Your program’s source files are to be submitted electronically on Gradescope. Please wrap everything in your
project folder (including asset files) to a zip file and submit it. Note that for this assignment, you will also need to
submit a simple reference image or concept drawing of your model.
3.2 Demo
Part of your grade for this programming assignment will be based on your giving a short demo (5-10 minutes) during
the CS480/680 scheduled labs following the assignment due date. You will be expected to talk about how your
program works, and will be asked related comprehension questions.
3.3 Reference image/drawing and screenshot
Please submit a reference image or drawing of your design and a corresponding screenshot. The image/drawing can
be relatively simple, and is simply to motivate some modeling with intent.
4. Grading
Students can receive at maximum 10 points of extra credit.
Task 480 680
3D Creature model constructed satisfies requirements for shapes, hierarchies, and color 25 25
Proper rotation at the joints 25 25
Limit rotation so that limbs do not bend in unnatural ways 10 10
Your predefined 5 creature poses work properly 25 25
The creature design is similar to your reference image/drawing 5 5
Eye movement 5 (extra) 15
Eye movement with quaternions 10 (extra) 10 (extra)
Programming style 10 10
5. Code Distribution Policy
You acknowledge this code is only for the course learning purpose. You should never distribute any part of this
assignment, especially the completed version, to any publicly accessible website or open repository without our
permission. Keep the code in your local computer or private repository is allowed. You should never share, sell, gift,
or copy the code in any format with any other person without our permission.
Appendix: Default Rotational Behavior
In order to simplify the process of constructing your model, the rotational origin of each Shape has been offset by
-1/2 * Δz, where Δz is the total length of the shape along its z-axis. In other words, the rotational origin lies along the
smallest local z-value rather than being at the translational origin, or the object’s true center. This allows Shapes to
rotate “at the joint” when chained together, much like segments of a limb. In general, this means that you should
construct each component such that it is longest in its local z-direction: otherwise, rotations may not
behave as expected.
If you would like to disable this behavior for a particular object, rotating it about its translational origin instead, you
can pass “limb = False” to the Shape constructor when creating the object. This is particularly useful for body parts
that do rotate about their centers, such as ball joints and eyes.
Below are some illustrations to show how this behavior works:
