Assignment 2: MeshEdit

MeshEdit is the first of three components of Scotty3D. The primary repository is located at The wiki on that page will be the primary source of information about this assignment, this document only contains administrative details about grading and submission.

Checkpoint: October 10th, 10:00pm (late-day ponts cannot be used towards this checkpoint; late hand-ins will incur a 10% penalty per day)

Due date: October 22nd, 10:00pm


For this assignment, you will implement methods in meshEdit.cpp.

The User Guide on the wiki describes a large number of features that are in principle available in MeshEdit mode. You do not have to implement all of these features to receive full credit on the assignment! However, you do have to successfully implement a subset of the features. Implementing additional features beyond the required subset will earn you extra credit points.

The particular requirements, and the percentage of the grade they correspond to, are:

  • Five of the local operations (listed below), including FaceBevel and one of EdgeCollapse or FaceCollapse (10 pts each)
  • Triangulation, LinearSubdivision, and CatmullClarkSubdivision (10 pts each)
  • One of: LoopSubdivision, IsotropicRemeshing, or Simplification (30 pts each)
  • Create one beautiful 3D model using Scotty3D (20 pts)
  • Writeup and commments for code (10 pts)
  • (Total score percentage is number of points out of 140)

And the total score will be the scores from the checkpoint (30 pts) and the second part (110 pts). See Checkpoint Evaluation below for details.

In other words, everyone has to implement FaceBevel, triangulation, linear subdivision, and Catmull-Clark. These features are the bare minimum needed to model interesting subdivision surfaces; triangulation is necessary in order to do the global remeshing task(s). And you need to choose at least one from EdgeCollapse and FaceCollapse(or both). Note that some of the global tasks will require that you implement specific local operations! For instance, if you plan on implementing Simplification, you should also choose to implement EdgeCollapse. The local operations are as follows (these operations are described in the User Guide):

  • VertexBevel
  • EdgeBevel
  • FaceBevel - everyone must implement
  • EraseVertex
  • EraseEdge
  • EdgeCollapse - everyone must implement this or FaceCollapse
  • FaceCollapse - everyone must implement this or EdgeCollapse
  • EdgeFlip
  • EdgeSplit

The global operations, and their dependency on local operations, are as follows:

  • Triangulation - everyone must implement
  • LinearSubdivision - everyone must implement
  • CatmullClarkSubdivision - everyone must implement
  • LoopSubdivision - depends on EdgeSplit and EdgeFlip
  • IsotropicRemeshing - depends on EdgeSplit, EdgeFlip, and EdgeCollapse
  • Simplification - depends on EdgeCollapse

You are free to change the subset of features you choose to implement at any point during the assignment, but you should clearly indicate which features you chose (including those implemented for extra credit) by putting this information in your writeup (described below).

Extra credit: each additional local operation beyond the requirements will be worth 2 pts; each additional global operation will be worth 4 pts.

The maximum possible grade on the assignment is 110%.

Checkpoint Evaluation

The 30 points for this checkpoint will be graded based on your submission on or before October 10th, 10:00pm. What you need to do are:

  • Implement local operation Facebevel (10 pts)
  • Implement local operation FaceCollapse or EdgeCollapse (10 pts)
  • Implement one of remaining local operations (10 pts)

To get full score for the first checkpoint, you should meet all the requirements above. Remember that if you start late and skip the checkpoint, the maximum score you can possibly get will be 110 out of 140 pts (excluding extra credit points). The score we give here (30 pts) is not proportional to the time we give for the checkpoint. Ideally, you should have finished more than just these three local operations. So remember to start early!

There is no extra credit for the checkpoint.

America's Next Top 3D Model

Every student is required to submit a 3D model created from cube.dae using their implementation of Scotty3D, which will be automatically entered into a class-wide 3D modeling competition. Models will be critiqued and evaluated based on both technical sophistication and aesthetic beauty. Note: Use of any other 3D package (e.g., free or commercial 3D modelers like Maya or Blender) is strictly prohibited! This model must be created by opening cube.dae, applying the operations implemented as part of the assignment, and saving the result.

NOTE: We are expecting some high-quality output here---or at least some creativity! Don't just brush this one off. :-)

Include this model in the root directory of your submission as model.dae.

Writeup and Comments

Additionally, you will submit a short document explaining what you have implemented, and any particular details of your submission. If your submission includes any implementations which are not entirely functional, please detail what works and what doesn't, along with where you got stuck. This document does not need to be long; correctly implemented features may simply be listed, and incomplete features should be described in a few sentences at most.

The writeup must be a pdf, markdown, or plaintext file. Include it in the root directory of your submission as writeup.pdf,, or writeup.txt.

You also need to write comments for your code so that when you code doesn't work, we can go through your code to give you partial credits.

If you fail to submit a writeup or there is no documentation for your code, you will lose points.

Code Environment

This codebase should compile on Linux, macOS, and Windows on a typical environment. The build instructions given on the project page will walk you through installing dependencies and building the code. If you have difficulties running the code on your local machine, the GHC 5xxx cluster machines have all the packages required to build the project.

Handin Instructions

As with the previous assignments, we will be submitting on Autolab. You should create a tar archive of your entire src subdirectory along with the writeup (e.g. writeup.txt) and 3D modeling submission (model.dae).

$ pwd
> (...)/Scotty3D
$ tar cvzf handin.tgz src/ writeup.txt model.dae
> a src
> a src/application.cpp
> a writeup.txt
> a model.dae

The Autolab system will run a simple script that checks for the extra files. If the output indicates that something is missing, fix it or risk losing points!