1 Overview
CS104 Project 1: Basic OpenGL Due Date: Sunday, Oct 20, 2019, 23:59:59
For this project, you will have the opportunity to familiarize yourself with basic OpenGL concepts and realtime graphics programming. You will implement basic camera and lighting functionality, and render a 3D mesh and a heightmap. You will find the OpenGL Programming Guide Red Book to be extremely helpful, as it covers nearly all topics needed for this assignment in great detail.
2 Description
The assignments are designed to give you an opportunity to implement some of the theoretical ideas that are discussed in lecture and a chance to program graphics applications.
For all assignments, we will direct you towards resources for help, but if you need more clarification or have a question, please contact TA: Miss Shang513462889qq.com.
For this particular assignment, the OpenGL redbook will be the most helpful resource.
We will be using OpenGL for almost all of the assignments, so this lab is an introduction to the library. Your task is to use OpenGL to render a simple 3D scene: a pool with animated water, in which you can move the camera around with mouse and keyboard input.
We will give you a scene with a model for our pool. The water will be represented as a heightmap. A heightmap is a function that defines a yposition for every point in the xzplane. We will be using this to create an animated surface of water by calculating the positions of points in the xzplane on each time step and constructing a polygonal mesh.
3 Submission Process and Handin Instructions
1. Failure to follow submission instructions will negatively impact your grade.
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You should submit all files needed to build your project, as well as any textures, models, shaders, or screenshots that you used or created. Your deliverables include:
src folder with all .cpp and .hpp files.
CMake build system.
writeup.txt
Any modelstexturesshaders needed to run your code.
Please do not include:
Anything in the build folder
Executable files
Any other binary or intermediate files generated in the build process.
Do not add levels of indirection when submitting. For example, your source directory should be at …andrewidp1src, not …andrewidp1myprojsrc or …andrewidp1p1.tar.gz. Please use the same arrangement as the handout.
We will enter your handin directory, and run cd buildrm rf cmake ..srcmake, and it should build correctly. The code must compile and run on the GHC 5xxx cluster machines. Be sure to check to make sure you submit all files and that it builds correctly.
The submission folder will be locked at the deadline. There are separate folders for late handins, one for each day. For example, if using one late day, submit to …andrewidp1late1. These will be locked in turn on each subsequent late day.
Required Tasks
A very general overview of the implementation requirements is as follows. Refer to subsequent sections of the handout for more details. Figure 1 shows a screenshot of the reference implementation.
Input: The input to the program is a hardcoded scene containing a model, a heightmap, a light, a camera, and some position and material properties, along with basic functionality for loading a window, saving screenshots, moving the camera with the mouse and keyboard, and running a rendering loop.
Output: The output is a rendering of this scene, in addition to screenshots and writeup.txt. Your code must compute the normals for the model and heightmap.
For your program, you must:
Correctly set the projection and modelview matrices based on the cameras values. The user should be able to move the camera around with the mouse and keyboard.
Generate a mesh for the heightmap.
Compute pervertex normals for the model and heightmaps meshes.
Use OpenGL fixedfunctionality to add lights to the scene to correctly shade the scene with the
given materials, setting appropriate ambient, diffuse and specular effects.
Submit a few screen shots of your programs renderings.
Use good code style and document well. We will read your code.
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Fill out writeup.txt with details on your implementation.
At a minimum, you must modify p1project.cpp and writeup.txt, though you may modify or add additional source files.
writeup.txt should contain a description of your implementation, along with any information about your submission of which the graders should be aware. Provide details on which methods and algorithms you used for the various portions of the lab. Essentially, if you think the grader needs to know about it to understand your code, you should put it in this file. You should also note which source files you edited and any additional ones you have added.
Examples of things to put in writeup.txt:
Mention parts of the requirements that you did not implement and why.
Describe any complicated algorithms used or algorithms that are not described in the bookhand out.
Justify any major design decisions you made, such as why you chose a particular algorithm or method.
List any extra work you did on top of basic requirements of which the grader should be aware.
Figure 1: Example program output
Starter Code
It is recommended that you begin by first reviewing the starter code provided. Though the amount you must edit is small, we are providing you with a large code base to get you started. You will need to get familiar with it, since much of it will be used in future projects as well. The README gives a breakdown of each source file.
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5.1 Programming Language
The code base is in C. We know that this may be a new language to many of you, and so it is limited to C and a small subset of C. In addition to C, the code uses classes, operator overloading, and a bit of the Standard Template Library, notably std::string and std::vector. If you are unfamiliar with these, your first task should be to learn them. The TAs are available for help.
5.2 Provided Functionality
The starter code provides a slew of functionality to get you started that is neither very interesting to write nor relevant for the course. You are free to modify any of it as you see fit, provided you do not break the application behavior. You may add any new behavior you wish. You will see the same code each project. Report any bugs to course staff. Here is a brief break down of what is provided; see the README for further details.
Matrix Algebra Structures and several helper functions for vectors, matrices, quaternions, and col ors. Most basic functions you would need e.g., dot product, matrixvector multiplication have been provided. Take a look before you write a basic math function to save yourself time. The function names and types are generally the same as those in the OpenGL Shading Language, which you will see in a future project.
Window InitializationEvent Handling SDL is used to initialize the window. The starter code creates a window and an OpenGL context, then runs a main loop that invokes updaterender functions at a consistent framerate. SDL is also used to process keyboard and mouse events.
Mesh Loading A class that loads an OBJ mesh into a list of vertices and triangles. In this project, only positions are provided for each vertex. Not all OBJ files are supported; consult the code for more detail.
Image SavingLoading Routines to saveload pngs into arrays of RGBA data. Also, the starter application code saves a screenshot when the f key is pressed.
5.3 Building and Running the Code
This project uses the CMake build system www.cmake.org. CMake is a kind of meta buildsystem, in that it creates a build system for you. It supports many different build systems, ranging from Unix Makefiles to Visual Studio projects to XCode projects.
If you dont have CMake installed, you should install it. If youre running Linux, it should be available through your distos package manager aptget, pacman, ports, etc. Windows and OSX installers can be downloaded from http:www.cmake.orgcmakeresourcessoftware.html
Open up a command prompt in the build directory and run cmake ..src. CMake will generate the build system in the build directory. By default, CMake will generate Makefiles on Linux and OSX and a Visual Studio project on Windows. If youd like to change that, you can pass a different generator to cmake with the G flag. A full list of generators can be found at the bottom of the output generated by running cmake. For example, cmake G Xcode ..src will generate an Xcode project on OSX.
You can now use the build system in the build directory. The default target will compile everything for you, and the install target will copy the p1 executable to the main p1 directory.
More details are in the README. If you use Windows, your project still must build and run on GHC Linux machines, so you will still have to test it on them before submitting. There are some differences in the compilers, so code that compiles and works with Visual Studio may not compile or run correctly with GCC. Make sure you test it well before the deadline. Be sure not to submit Windows binaries, either.
The program takes no arguments as the scene is hardcoded. Simply run the resulting executable. 4
5.4 What You Need to Implement
p1project.cpp contains some empty shell functions for you to fill in. At a minimum, you should implement the initialize, destroy, update, and render functions. Documentation for each function is in the source file. Feel free to modify any existing code or add new files, as long as you do not break the behavior of the program.
6 Grading: Visual Output and Code Style
Your project will be graded both on the visual output both screenshots and running the program and on the code itself. We will read the code.
In this assignment, part of your grade is on the quality of the visuals, in addition to correctness of the math. So make it look nice. Extra credit may be awarded for particularly goodlooking projects.
Part of your grade is dependent on your code style, both how you structure your code and how readable it is. You should think carefully about how to implement the solution in a clean and complete manner. A correct, wellorganized, and wellthoughtout solution is better than a correct one which is not.
We will be looking for correct and clean usage of the C language, such as making sure memory is freed and many other common pitfalls. These can impact your grade. Additionally, we will comment on your Cspecific usage, though we will generally be more lenient with points at least earlier in the semester. More general style and Cspecific style i.e., rules that apply in both C and C will, however, affect your grade.
Since we read the code, please remember that we must be able to understand what your code is doing. So you should write clearly and document well. If the grader cannot tell what you are doing, then it is difficult to provide feedback on your mistakes or assign partial credit. Good documentation is a requirement.
7 Implementation Details
The Red Book is essential for this project. The first few chapters provide all the information you need to render the scene using OpenGL. Consult the Red Book or online resources for descriptions of the API.
7.1 UpdateRender Loop
The starter code runs an updaterender loop at a fixed framerate. The update function is always invoked, but the render function may be skipped if the framerate is lagging. Thus, update and render may not correlate exactly. Your program must maintain a reasonable framerate.
7.2 Scene Representation
The scene is described by structs in p1project.hpp. The scene consists of a camera, a triangle mesh, and a heightmap. The triangle mesh and heightmap also both have an associated position, orientation, and scale. The following sections describe each of these in more detail. Note that no materiallighting information is specified; you can use whatever you like for these. However, for all other values including the camera, you must use all the given values.
7.3 Projection and Transformation
The camera class contains all information needed to position a camera in a scene. OpenGL matrix stack is used for transformations; consult the Red Book for more detail. The projection matrix
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typically contains the cameras field of view FOV, aspect ratio, and near and far planes. You may find gluPerspective useful here. The modelview matrix contains the cameras position, direction, up vector, and the models position, orientation, and scale. You may find gluLookAt useful here.
Note: gluLookAt takes a camera target, which is not the same as the camera direction. Read the documentation carefully.
7.4 Object Transformations
Both the mesh and heightmap come with a position, orientation and scale. These are defined as a vector, quaternion, and vector, respectively. Traditionally in OpenGL, the modelview matrix is used to store object transformations, which are applied after camera transformations. The Red Book describes this in detail, including using the modelview matrix to share camera transforms and objects transforms.
Note: glScale will cause normals to not be of unit length, which messes up lighting. See GL NORMALIZE for details on fixing this problem.
7.4.1 About Quaternions
Quaternions are a compact, efficient way to represent 3dimensional rotations. You do not need to understand the inner workings of quaternions, but for those interested, they parallel how complex numbers are used to represent rotations in 2 dimensions. The given implementation provides functions to convert to and from either a 33 matrix or an axisangle format. That should be all you need to use them for this and other labs, although you are encouraged to study and use the quaternion libraries directly in future labs.
7.5 Rendering Triangle Meshes
A Mesh consists of a list of triangles and a list of vertices. A triangle is simply three indices into the vertex list. Vertices are a position in 3D space along with other attributes such as the normal. For this lab, you will actually be computing the normal yourself, so only position is provided.
The Red Book describes several methods for rendering a triangle mesh, and you may use any that you wish. If you are new to OpenGL, the course staff recommends using vertex arrays. Essentially, they work by putting all the primitive data into arrays and drawing the entire array with one function call. They are simple to use yet vastly more efficient than more basic methods though still nowhere near the most efficient. As always, see the Red Book for more details.
Vertex Buffer Objects VBOs are a slightly more recent addition to OpenGL. As such, they are not covered in the Red Book and are not provided by the default OpenGL shared library. The starter code provided to you includes the GL Extension Wrangler GLEW, which loads in all OpenGL extension functions that are supported by your graphics hardware. Though VBOs are an extension, they were released in 2003 and are therefore supported by virtually all graphics hardware.
A good overview of VBOs is available at http:www.songho.caopenglglvbo.html. NOTE: The functions and constants exported by GLEW do not include the ARB suffixes. For example, use glGenBuffers, not glGenBuffersARB and GL STATIC DRAW, not GL STATIC DRAW ARB.
More information about GLEW is available at http:glew.sourceforge.net. 7.6 Computing the Heightmap Mesh
The heightmap will also be a mesh, only you must create it yourself. The Heightmap is an interface that provides a function to query the y position height at a given x,z position, from 1,1 to 1, 1. To render this, you must create a mesh from the heightmap by breaking it into discrete points
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on a grid, evaluating the heightmap at each point to get vertex positions, and connecting them into a mesh. The resolution of this mesh should be at least 64 vertices in each direction.
We actually provide you with an animated heightmap, so youll have to recompute the mesh and normals in the update function. Most reasonable implementations will be more than fast enough, but take care that your program maintains a reasonable framerate.
Note: It is a poor idea to allocate new memory for this mesh every frame. Repeated allocations via malloc or new are extremely slow.
7.7 Buffers
The rasterized primitives are placed in the color buffer, which is the final image placed on the screen. This color buffer is not cleared automatically each frame, and so you must do this manually. Look at glClear to accomplish this.
You must use the depth buffer to make sure the correct primitives are drawn. Closer primitives should be drawn on top of farther primitives. You can use OpenGLs depth test for this. You must enable this manually. As with the color buffer, the depth buffer is not automatically cleared.
7.8 Lighting the Scene
Once you render meshes correctly with the transformation matrices set correctly, you should be able to see a solid silhouette. The last task is to add some lighting to the scene to provide somewhat realistic looking shading.
The Red Book has entire chapters on lights and materials. We will only make you do the very basics for this assignment. Create at least one single light for your scene, and set some ambient, diffuse, and specular materials for your object in order to light it. You can also play with the color. Use different materials for each object.
7.9 Computing Normals
For lighting to work correctly, you will need normal data for your model. We intentionally do not load any normals from the model file; you must compute them yourself. You will be implementing a numerical approximation of the normal for each vertex:
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Compute the normal for each triangle. Respect the winding order convention: the default for OpenGL is that primitives are in counterclockwise order. You should normalize this vector. Set the normal for a particular vertex to be the average of the normals of all triangles of which it is a part.
Suggested Sequence
We suggest you implement the assignment in the following order:
1. Create a test object to get basic rendering working.
2. Use the transformation matrices to account for the virtual camera and object transformations. 3. Render the given mesh without lightingnormals.
4. Use the matrices to follow objects positions.
5. Compute normals for the mesh and add a light to the scene.
6. Create a mesh with normals from the heightmap and render it.
7. Create materials for each object.
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Words of Advice
Start early. Though this assignment is simple, it may take you time to become familiar with the OpenGL API and this style of programming. There are a lot of concepts introduced. Familiarize yourself with all the OpenGL concepts transformation matrices, primitive rendering, lighting, materials, etc before starting the assignment. The Red Book covers all these topics, as do many sources on the internet.
Familiarize yourself with the structures in math before starting, as they will be used throughout the semester. In particular, have a look at the Vector and Camera structures.
Start with a simple object, even a hardcoded one like a triangle, to get something working. Make sure you have a submission directory that you can write to as soon as possible. Notify course staff if this is not the case.
Experiment! Play around with OpenGL, even features that arent part of the assignment. There is a lot you can do.
While C has many pitfalls, C introduces even more wonderful ways to shoot yourself in the foot. It is generally wise to stay away from as many features as possible, and make sure you fully understand the features you do use.
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