Description

CENG477
Introduction to Computer Graphics
Assignment 3 – A Software Rasterizer using OpenGL

1 Objectives
Keywords: OpenGL, fixed pipeline, modeling transformations, viewing transformations
2 Specifications
1. The name of the executable will be “hw3”.
2. Your executable will take an XML file name from command line. Input file names are not static, they can be anything. XML file has minor differences from first and second assignments. It has only one camera and Transformations tag. The only object type included in this homework is Mesh.
3. You will be given a sample makefile. You can extend it or use as it is. However, be sure, before submitting, it is running on Inek machines. The executable should be run with the ”./hw3 sample input.xml” command smoothly. It will not produce any outputs since an OpenGL display window will be used.
4. You can use “X11 forwarding” to work on Inek machines. To do so, you need to first connect to login.ceng.metu.edu.tr (not external.ceng.metu.edu.tr) through ssh with -X flag. After you reached the login lobby machine, you need to connect to any of the inek machines with -X flag.
5. You will compute normal vectors of vertices as the average of the normal vectors of the triangles incident to this vertex.
7. Models will be rendered in solid or wireframe modes as specified in the input file. Use the OpenGL function call glPolygonMode(GL FRONT AND BACK, GL FILL); for the solid and the call glPolygonMode(GL FRONT AND BACK, GL LINE); for the wireframe modes, respectively.
8. You will not compute lightings explicitly. It will be done automatically by calling appropriate OpenGL functions.
9. In both wireframe and solid modes, triangles whose backface or frontface to the viewer will be culled according to the parameter in the input file. Backface/frontface culling should be enabled/disabled according to the setting in input file. CullingEnabled can be 0 (disabled) or 1 (enabled) and CullingFace can be 0 (backface) or 1 (frontface).
10. Use the smooth shading mode of OpenGL by calling the function glShadeModel(GL SMOOTH);.
12. You will show the FPS (frame-per-second) in the title. The title will look like to the one in the sample image.
13. Helper functions for reading inputs are given to you. It is STRONGLY recommended to inspect types in header files and helper functions, which are given to you in homework stub code.
3 Sample input/output
Sample input files are given at COW. The initial view of the OpenGL display window for the horse and mug input is shown in the image below where the horse is rendered as a filled mesh whereas the mug is rendered as wireframe.

4 Hints & Tips
1. Start early!
2. When lighting is enabled, OpenGL does not use glColor to color the surfaces by default. Instead, surface material properties are defined using the glMaterialfv function. To set the color of surface (or the entire model), use the following piece of code just before drawing the object.
GLfloat ambColor [4] = {<ar>, <ag>, <ab>, 1.0};
GLfloat diffColor [4] = {<dr>, <dg>, <db>, 1.0};
GLfloat specColor [4] = {<sr>, <sg>, <sb>, 1.0}; GLfloat specExp [1] = {<specular exponent>};
glMaterialfv(GL_FRONT , GL_AMBIENT , ambColor) ; glMaterialfv(GL_FRONT , GL_DIFFUSE , diffColor) ; glMaterialfv(GL_FRONT , GL_SPECULAR , specColor) ; glMaterialfv(GL_FRONT , GL_SHININESS , specExp) ;
Finally, to determine the amount of light reflected from the surfaces correctly, you should specify the normal vectors of the vertices.
5 Regulations
1. Programming Language: C++
2. Late Submission: Refer to the syllabus for the late policy.
3. Groups: You can team-up with another student. But you must notify the assistants about who your partner is within the allowed time frame.
5. Newsgroup: You must follow the ODTUCLASS forum for discussions, possible updates, and corrections.
6. Submission: Submission will be done via ODTUCLASS. Create a “tar.gz” file that contains all your source code files and a makefile. The executable should be named as “hw3” and should be able to be run using the command “./hw3 scene file name.xml”. The .tar.gz file name should be:
• If a student works with a partner student:
<partner_1_student_id>_<partner_2_student_id>_hw3.tar.gz
• If a student works alone:
<student_id>_hw3.tar.gz
• For example:
1234567_2345678_hw3.tar.gz
1234567_hw3.tar.gz
7. Evaluation: Your codes will be evaluated on Inek Machines; based on several input files including, but not limited to the test cases given to you as examples. Evaluation will be done manually, small differences might be tolerated.