Ucc的week16上課筆記~

# Week16
 ## 電腦圖學 Week16 2022-06-07
```
1. 主題: 內插、動作內插
2. 主題: 攝影機、運鏡 
3. 實作: gluLookAt()
```
## step01-1 Alpha內插公式    =>   alpha: 0.0~1.0
>>> angle=alpha*新+(1-alpha)*舊
```
ex.
-  alpha:0  =>  舊
-  alpha:0.5  =>半新半就
-  alpha:1  =>新

可以使用Excel or Google Spreadsheet 來做
```

## step01-2 用程式試試看(●´ω｀●)ゞ
>>> 使用上週 week15_angles_TRT_again 改動

```C

1.File-New-Project-GLUT專案-week16_interpolation 內插

2.複製程式=>執行=>mouse motion改動作,按s存檔一行關節動作*4次

3.按r之後發現動作不連續

```

## 改造程式碼

```C

1.void myInterpolate(float alpha)

2.一樣按s儲存每個動作

3.按下p可以逐步計算內插,做新舊角度交換

    if(key=='p'){///play

            if(t%30==0) myRead();///介於0.0~1.0

            myInterpolate((t%30)/30.0);

            glutPostRedisplay();

            t++;

        }

=>>動畫變得更順👍👍

```

## step02-1 讓動畫跑得更順(將myInterpolate在timer裡呼叫)

```

1.透過上一節課的程式碼進行修改

2.將原本的一直按著p改成按一次p可以自動重複撥放

3.timer計時器可以設定幾秒撥一次動畫

4.%50的原因是因為這樣計算下來每1秒會跑一格動畫

```

## 目前程式碼

```C

///week15修改自week14_angles_fprintf

///week16_interpolation

#include <GL/glut.h>

#include <stdio.h>

float angle[20],oldX=0;

int angleID=0;

FILE * fout=NULL, * fin = NULL;

void myWrite()

{///每呼叫一次myWrite

    if(fout == NULL)fout=fopen("file.txt","w+");

    for(int i = 0;i<20;i++)

    {

        printf("%.1f ",angle[i]);///小黑印出來

        fprintf(fout,"%.1f ",angle[i]);///檔案印出來

    }///這裡老師沒有fclose

    printf("\n");///小黑印出跳行

    fprintf(fout,"\n");///檔案跳行

}

float NewAngle[20],OldAngle[20];

void myRead()

{

    if(fout!=NULL){fclose(fout); fout=NULL;}

    if(fin==NULL) fin=fopen("file.txt","r");

    for(int i=0;i<20;i++)

    {

        OldAngle[i]=NewAngle[i];///原來新的變舊

        fscanf(fin,"%f",&NewAngle[i]);///得到新角度

        ///fscanf(fin,"%f",&angle[i]);

    }

    glutPostRedisplay();///重劃畫面

}

void myInterpolate(float alpha)

{

    for(int i=0;i<20;i++)

    {

        angle[i]=alpha*NewAngle[i]+(1-alpha)*OldAngle[i];

    }

}

void timer (int t)

{  if(t%50==0) myRead();

    myInterpolate((t%50)/50.0);

    glutPostRedisplay();

    glutTimerFunc(20,timer,t+1);

}

///int t=0;

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

{

    if(key=='p'){///play

            myRead();

            glutTimerFunc(0,timer,0);

        ///if(t%30==0) myRead();///介於0.0~1.0

        ///myInterpolate((t%30)/30.0);

        ///glutPostRedisplay();

        ///t++;

    }

    if(key=='s') myWrite();///調好動作才save存檔

    if(key=='r') myRead();

    if(key=='0') angleID=0;

    if(key=='1') angleID=1;

    if(key=='2') angleID=2;

    if(key=='3') angleID=3;

}

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

{

    oldX=x;

}

void motion(int x,int y)

{

    angle[angleID]+=(x-oldX);

    ///myWrite();

    oldX=x;

    glutPostRedisplay();

}

 void display()

 {

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glColor3f(1,1,1);

    glRectf(0.3,0.5,-0.3,-0.5);

    glPushMatrix();

        glTranslatef(0.3,0.4,0);

        glRotatef(angle[0],0,0,1);

        glTranslatef(-0.3,-0.4,0);

        glColor3f(1,0,0);

        glRectf(0.3,0.5,0.7,0.3);

        glPushMatrix();

            glTranslatef(0.7,0.4,0);

            glRotatef(angle[1],0,0,1);

            glTranslatef(-0.7,-0.4,0);

            glColor3f(0,1,0);

            glRectf(0.7,0.5,1.0,0.3);

        glPopMatrix();

    glPopMatrix();

        glPushMatrix();

            glTranslatef(-0.3,0.4,0);

            glRotatef(angle[2],0,0,1);

            glTranslatef(0.3,-0.4,0);

            glColor3f(1,0,0);

            glRectf(-0.3,0.5,-0.7,0.3);

            glPushMatrix();

                glTranslatef(-0.7,0.4,0);

                glRotatef(angle[3],0,0,1);

                glTranslatef(0.7,-0.4,0);

                glColor3f(0,1,0);

                glRectf(-0.7,0.5,-1.0,0.3);

            glPopMatrix();

    glPopMatrix();

    glutSwapBuffers();

 }

 int main(int argc, char *argv[])

 {

    glutInit(&argc,argv);

    glutInitDisplayMode(GLUT_DOUBLE|GLUT_DEPTH);

    glutCreateWindow("week16_interpolation");

    glutMouseFunc(mouse);

    glutMotionFunc(motion);

    glutKeyboardFunc(keyboard);

    glutDisplayFunc(display);

    glutMainLoop();

 }

```

## Step02-2 運鏡

```

eye=>眼睛座標位置

center=>看哪裡位置

up=>向量(攝影機指向的地方)

謝謝老師熱情的代入教學

```

##  Step03-1 保持長寬比

>>> 不會變形

```

1.File-New-Project-GLUT專案-week16_camera_projection_GlutLookat

2.備份177行範例,透過那段程式進行修改

3.aspect ratio 長寬比(左寬右高) ex.1920x1080 1280x720 640x480,16:9,4:3....

```

## 在做一些改動

```

1.新增void motion函式

2.原本視角固定在0,0,3的位置=>(x-150)/150.0,(y-150)/150.0,3, ///eye

   (透過滑鼠的滑動做出視窗的轉變)

```

## 現在程式碼

```C

#include <GL/glut.h>

void reshape(int w,int h){///不能 整數除

    float ar = (float) w/(float) h;

    glViewport(0,0,w,h);

    glMatrixMode(GL_PROJECTION);///3D變2D

    glLoadIdentity();

    gluPerspective(60,ar,0.1,100);

    glMatrixMode(GL_MODELVIEW);///3D Model+view

    glLoadIdentity();

    gluLookAt(0,0,3, ///eye

              0,0,0, ///center看哪裡

              0,1,0);///up向量

}

void display()

{

    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

    glutSolidTeapot(1);

    glutSwapBuffers();

}

void motion(int x,int y)

{

    glMatrixMode(GL_MODELVIEW);///3D Model+view

    glLoadIdentity();

    gluLookAt((x-150)/150.0,(y-150)/150.0,3, ///eye

              0,0,0, ///center看哪裡

              0,1,0);///up向量

    glutPostRedisplay();///重劃畫面

}

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

{

    glutInit(&argc, argv);

    glutInitDisplayMode(GLUT_DOUBLE | GLUT_DEPTH);

    glutCreateWindow("week16 camera");

    glutDisplayFunc(display);

    glutMotionFunc(motion);

    glutReshapeFunc(reshape);///範例是resize

    glutMainLoop();

}

```