Homework 5: Views && Perspective

Computer Graphics

2017-04-10

1. Introduction

So far we have learn how to move the objects in the virtual world, but it seems that we always observe the virtual world in a fix position. Hence, let’s move around and look around on this world! In this homework, you are required to manipulate the view/camera in OpenGL and to know the differences and correlation between this homework and homework6.

Warning： All codes and documents should be written and submitted individually, without copying existed answers (Neither from other student nor from the Internet). Plagiarism = Fail. Besides, there may be at least 30% penalty for late homework.

2. Tasks

2.1 Pre-requirement

Language: Only C/C++ is accepted in this homework.
Libraries: Only OpenGL and freeGLUT/GLFW can be used.
OS/IDE: Any OS/IDE can be used.
The cube you’ve drawn in homework4 is needed. Each face of the cube should be colored differently. The size of the cube should be 0.1x0.1x0.1.

2.2 Projections

Projection define how a virtual 3D world projects into a 2D screen such that we can see it. There are 2 kinds of projections are used in OpenGL: perspective projection and orthographic projection.

Place the cube in (0.5,-0.5,-1.5) and create a orthographic projection. Show what you get in the report. Try different parameters(i.e. left, right, bottom, top, near, far), and write down how these parameters affect result in the report.
Place the cube in (0.5,-0.5,-1.5) and create a perspective projection. Show what you get in the report. Try different parameters, and write down how these parameters affect result in the report.
Use exactly same parameters for 2 projections and discuss the differences of 2 results. Post the result in your report and discuss why.
Write down your main algrithm in the report.

2.3 View Changing

You are required to change the view of the camera to observe the cube.

Place the cube in (0,0,0), use the perspective projection. Import glu.h, try gluLookat(...) function. Let your camera circle around the cube, but looking at the cube all the time.
Show the results and write down your main algrithm in the report.
In practice, the camera setting is actually stored in a matrix called View matrix. The transformations is also stored in a matrix called Model matrix. However, in OpenGL, these two matrices is actually one matrix called ModelView matrix. Discuss why it is so in the report. (Hints: Is there an actual camera object in virtual world? If there is not, how to pretend we have one?)

Hints: You may want to change your camera position in a circle. Try:

camPosX=sin(clock()/1000.0)*Radius;
camPosZ=cos(clock()/1000.0)*Radius;

Since sin(x)^2+cos(x)^2=1, that make sure we form a circle in XoZ plane.

2.4 Bonus: the Camera Class

Implement a Camera class to provide a FPS (First Person Shooting) view, which means when you press w,a,s,d, it would feel like if you were ‘walking around’ in the virtual world. When you move your mouse, it would feel like if you were ‘looking around’.

Hints:
The header of the Camera may be:(You can change it if you like)

class Camera{
public:
	...
	void moveForward(GLfloat const distance);
	void moveBack(GLfloat const distance);
	void moveRight(GLfloat const distance);
	void moveLeft(GLfloat const distance);
	...
	void rotate(GLfloat const pitch, GLfloat const yaw);
	...
private:
	...
	GLfloat pfov,pratio,pnear,pfar;
	GLfloat cameraPosX,cameraPosY,cameraPosZ;
	GLfloat cameraFrontX,cameraFrontY,cameraFrontZ;
	GLfloat cameraRightX,cameraRightY,cameraRightZ;
	GLfloat cameraUpX,cameraUpY,cameraUpZ;
	...
};

P.S. In the method void Camera::rotate(GLfloat const pitch, GLfloat const yaw), ‘pitch’ and ‘yaw’ means the Euler angles. Euler angles are 3 values that can represent any rotation in 3D, defined by Leonhard Euler somewhere in the 1700s. The following image gives them a visual meaning:

3. Submitting Format

Please submit your homework to sysucg2017@163.com. You subject of the email should be as same as your attachment(aka. your .zip file)

Only a .zip file should be submitted. Under the .zip file, the content should look like this:

classTpye_studentID_Name_hw?_version?/
　　|— src/
　　|— doc/
　　|— bin/

classType: R for required class(必修班); E for elective class(选修班).
studentID: 1xxxxxxx
Name: Your Chinese Name.
hw?: Specific which homework you are submitting.
version?: Specific if you modify your submitted homework, only the last version would be graded. Started with version0.
src/: The folder holds your project, including source files.(Make sure you execute the clean command, we don’t need those temporary files)
doc/: Only one PDF should be included.
bin/: Executable program and a ReadMe.txt to tell us how to run your program.

For example, a student in required class want to submit homework2 for the second time, his .zip file should be:

　　R_16214382_伊利丹·怒风_hw2_version1.zip
　　　　|—R_16214382_伊利丹·怒风_hw2_version1/
　　　　　　｜—src/ 　　　　　　——放整个工程
　　　　　　｜—doc/ 　　　　　　——放report.pdf
　　　　　　｜—bin/ 　　　　　　——放可执行文件和readme