COMP4610 Computer Graphics Assignment 1: OBJ Mesh and Spatial Transformations
Computer Lab Homework Assignment #1, S1 2024
Topic: Environment preparation and basic geometry transformations.
Date Issued: see Wattle page Due Date: see Wattle page
Weighting: 12%
Instruction:
All homework assignments must be completed individually.
We encourage you to discuss the assignments with other students. However, you should not share any of your codes with anyone else. Each student is responsible for implementing the assignment on their own. You may assist other in debugging their codes, but you should not copy and paste. ANU is using Turnitin to detect possible duplications. Consulting with previous year students who enrolled in this course on specific assignment is also not allowed. You may use the internet as a resource for learning the materials, but you should not borrow any existing codes found online.
The homework assignments involve a significant amount of C/C++ programming. However, for most cases, a skeletal code base is provided, and you only need to fill in the missing parts, and/or fix bugs if any.
You will submit a single ZIP file as your submission, which must contain the following files:
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(1) All source codes (ending in .h, or .hpp, or .cpp), and CMakeLists.txt. Please include all needed source codes for successful compilation. Please also remove all intermediatefilesandfolders(suchas.vscode/andbuild/) thatarenotneeded for the compilation – Failing to do so will lead to penalty to the marks.
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(2) A written CLab1-Report (minimum 10-point font size, single column A4, in PDF format, with task statement, methods used, any new features that you have implemented, any known bugs in your code, answer any questions that have been asked in the task, instruction for the tutor to use your code, example experiment results. )
Your ZIP file must be named as “COMPX610_2024_HW1_UID.zip”. Replace ‘X’ with 4 or 8. Replace the UID with your Uxxxxxxxx; Please submit your ZIP file to Wattle before the deadline. Late submission will lead to penalty as per the ANU policy. Later-than-one-week
submission will not be accepted, which may result zero mark, unless a pre-approval for special consideration is obtained in written before the submission deadline.
Tasks for HW1:
Task-1: C/C++ Programming Basics
We will introduce basic C/C++ programming knowledge including development environment, fundamental syntax and constructs of C/C++ project that will be used in the homework assignments. If you come across any further problems with C/C++, please refer to online resources C++ documentation — DevDocs, Stack Overflow – Where Developers Learn, Share, & Build Careers or post on Ed Forum.
1.1 Development Environment
We use Visual Studio Code (VSCode) as our IDE (Integrated Development Environment). It’s
already installed and set up in the virtual machine. You can use VSCode to open your project.
1.2 C++ Programming
1.2.1 Basic programming
First, you need to include essential header files at the front of the code.
Define a main function as the entry of your program.
Call some mathematic functions.
1.2.2 Vector manipulation with Eigen library
Eigen is a C++ library for linear algebra, matrix and vector operations. Please refer to
use_eigen.cppforsomecommonusageofEigenandmoreinformationat Eigen:Quick
reference guide.
1.3 Organize your project with CMake
CMake is an open-source, cross-platform family of tools designed to build, test and package
software. CMake is used to control the software compilation process using simple platform
and compiler independent configuration files and generate native makefiles and workspaces
that can be used in the compiler environment of your choice.
1.3.1 Writing a CMakeLists.txt
CMake uses a configuration file called CmakeLists.txt to organize a project. Below is a
minimum example of CmakeLists.txt with detailed comments.
1.3.2 Configure with CMake
To use CMake in VSCode, press CTRL + SHIFT + P to open the Command Palette and select CMake: Configure.
Choose GCC as the project compiler.
Then, VSCode will invoke CMake to setup the project according to the provided
CmakeLists.txt and generate a build folder under the project root directory.
Build the project in the terminal by cmake .. && make:
1.4 Debug with VSCode
Select a build target at the bottom status bar.
Set a breakpoint at the target line by click or press F9.
Press CTRL+F5 to start debugging.
1.5 Check if a point is inside a triangle:
In computer graphics, determining whether a point is inside a triangle on the plane is a very
popular algorithm. You need to implement this algorithm according to the lecture in the
provided code framework task1.cpp.
Task-2: OBJ Mesh file I/O and operations:
Get yourself familiar with Wavefront OBJ file format by reading the Wikipedia page: Wavefront .obj file - Wikipedia.
You need to complete the following two sub-tasks:
(a) Find the provided mesh Cottage.obj in the model folder and visualize it with
MeshLab.
(b) Create a simple house mesh by hand (which means you can only create the mesh in a
text editor without any 3D software) and save it as house.obj in the model folder. Basically, the house mesh should contain a cuboid base, a triangular prism roof and a chimney. Note that you only need to create the vertices and faces of the mesh.
Figure: An example of a simple house mesh.
Task-3: Spatial Transformations for Graphics Rendering
From the first two weeks, you have learned how to use transformation matrices to prepare an object for graphics rendering. Now it is time to put them into practice. In this task, we will create a house mesh and display it in the screen. You need to finish the task by following steps:
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(a) Implement the get_model_matrix function that calculates a transformation matrix given the rotation angle, translation and scale.
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(b) Implement a draw_circle function according to the lecture slides.
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(c) Currently, the camera is fixed and always looking towards the -z direction.
Please update your code to enable camera movement by keyboard and ensure the camera is always looking at the origin. To do this, you may need to implement the look_at function and used it in the get_view_matrix function. -
(d) Run your code to see the result.
Task-4: Spatial transformations
4.1. In order to perform geometric transformations of a rigid body in 3D space, we often use 4x4 homogeneous matrices. Write down any 4x4 matrix which represents a rigid Euclidean transformation and prove that your specific 4x4 matrix is indeed a rigid Euclidean transformation.
4.2. Write the homogeneous transformation matrix that rotates a point around the Y-axis by 90 degrees with the centre at point (2, 3, 4). Please list the steps of your calculation.
4.3. Given the 3D cube mesh cube.obj with 12 triangles. Use this cube as the primitive shape, write some C++ codes to model the following cubic dog using transformed primitive cuboids, and render it as wireframe. Report your rendering result in your Lab report.
Figure: A dog modelled with translated, rotated, and scaled cuboids. (Courtesy of Morgan McGuire).
How to compile and run your codes?
Library dependencies: Eigen, and OpenCV;
Please use the following commands in order, to compile and test your code.
(1) mkdir build
(2) cd build
(3) cmake ..
(4) make -j4
Report Template and Marking Criteria:
Please use “CLab#1 report template” to write your Lab report. Marking Criteria” posted on Wattle.
Please also note the “HW1
Your ZIP file must be named as “COMPX610_2024_HW1_UID.zip”. == END OF CLAB-1 ==
