從0到0.01的電腦圖學 Week04

本週主題：

a. 鍵盤、滑鼠、motion

b. 移動、旋轉、縮放

c. 矩陣

1. GLUT程式1：縮放

將上週程式做調整，加入glScalef()可以做圖形的縮放操作

#include <GL/glut.h>
float s=1; ///縮放比例
void display(){
    glClearColor(0.5,1.0,1.0,1.0); ///清背景的水藍色
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT); ///清背景
    glPushMatrix();
        glScalef(s,s,s);
        glutSolidTeapot(0.5);
    glPopMatrix();
    glutSwapBuffers();
}
void motion(int x,int y){
    s = 1 +(x-150)/150.0;
    display();
}
int main(int argc,char*argv[]){
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_DOUBLE|GLUT_DEPTH);
    glutCreateWindow("week04 mouse glScalef");
    glutDisplayFunc(display);
    glutMotionFunc(motion);
    glutMainLoop();
}

2. GLUT程式2：獲取鍵盤按鍵+鼠標當前位於畫面座標值

使用glutKeyboardFunc()可以獲取鍵盤按鍵與滑鼠座標...等資訊

#include <GL/glut.h>

#include <stdio.h>

void display(){

    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

    glutSolidTeapot(0.5);

    glutSwapBuffers();

}

void keyboard(unsigned char key,int x,int y){

    printf("key: %c x: %d y: %d\n" ,key,x,y);

}

int main(int argc, char *argv[]){

    glutInit(&argc, argv);

    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);

    glutCreateWindow("week04 keyboard mouse motion");

    glutDisplayFunc(display);

    glutKeyboardFunc(keyboard);

    glutMainLoop();

}

3. GLUT程式3：對上一個程式做修改，使其可以因為紀錄舊的值而對當前狀態直接修改

#include <GL/glut.h>

#include <stdio.h>

float angle = 0, oldX = 0;

void display(){

    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

    glPushMatrix();

        glRotatef(angle,0,0,1);

        glutSolidTeapot(0.5);

    glPopMatrix();

    glutSwapBuffers();

}

void mouse(int button,int state, int x,int y){

    oldX = x; ///當mouse按下時,紀錄位置

}

void motion(int x,int y){

    angle += (x-oldX);

    oldX = x;

    display();

}

void keyboard(unsigned char key,int x,int y){

    printf("key: %c x: %d y: %d\n",key,x,y);

}

int main(int argc, char *argv[]){

    glutInit(&argc, argv);

    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);

    glutCreateWindow("week04 keyboard mouse motion");

    glutDisplayFunc(display);

    glutKeyboardFunc(keyboard);

    glutMouseFunc(mouse);

    glutMotionFunc(motion);

    glutMainLoop();

}

4. 範例程式碼：

5. 自轉與公轉

note：由後往前理解物件改變

a. 自轉

glTranslatef() -> glRotatef() -> glScalef()：
調整拉伸->物件自轉->移動物件

b. 公轉

glRotatef() -> glTranslatef() -> glScalef()：
調整拉伸->移動物件->物件以中心公轉

6. GLUT程式4：將茶壺移至右方，並使其自轉

a. 加入glutIdleFunc();讓每一次的loop都可以更新畫面

b. 加入glTranslatef()、glRotatef()、glScalef()

#include <GL/glut.h>

#include <stdio.h>

float angle = 0;

void display(){

    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

    glPushMatrix();

        glTranslatef(0.8,0,0);

        glRotatef(angle+=0.01,0,0,1);

        glScalef(0.3, 0.3, 0.3);

        glutSolidTeapot(0.5);

    glPopMatrix();

    glutSwapBuffers();

}

int main(int argc, char *argv[]){

    glutInit(&argc, argv);

    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);

    glutCreateWindow("week04 translate rotate scale");

    glutDisplayFunc(display);

    glutIdleFunc(display);

    glutMainLoop();

}

7. GLUT程式5：茶壺移離中心，並使其以中心公轉

對上面的程式碼調整glTranslatef()、glRotatef()、glScalef()的次序，詳細可參考5.自轉與公轉

#include <GL/glut.h>

#include <stdio.h>

float angle = 0;

void display(){

    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

    glPushMatrix();

        glRotatef(angle+=0.01,0,0,1);

        glTranslatef(0.8,0,0);

        glScalef(0.3, 0.3, 0.3);

        glutSolidTeapot(0.5);

    glPopMatrix();

    glutSwapBuffers();

}

int main(int argc, char *argv[]){

    glutInit(&argc, argv);

    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);

    glutCreateWindow("week04 translate rotate scale");

    glutDisplayFunc(display);

    glutIdleFunc(display);

    glutMainLoop();

}

Do you ever get a little bit tired of life
Like you're not really happy but you don't wanna die
Like you're hanging by a thread but you gotta survive
'Cause you gotta survive

A little bit tired of tryin' to care when I don't
A little bit tired of quick repairs to cope
A little bit tired of sinkin'
There's water in my boat
I'm barely breathin'
Tryna stay afloat
So I got these quick repairs to cope
Guess I'm just broken and broke

----Numb Little Bug , Em Beihold