[译]GLUT教程

Lighthouse3d.com >> GLUT Tutorial >> Pop-up Menus >> The Code So Far III

这里我们准备包含一些前面几节展示过的素材.我们准备添加菜单到应用程序,子菜单和菜单交换.

直接复制粘贴下面代码到你的项目.鼠标右键会打开菜单.按键's'和'c'会生效到菜单选项.

#include <stdlib.h>
#include <math.h>

#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif

// angle of rotation for the camera direction
float angle = 0.0f;

// actual vector representing the camera's direction
float lx=0.0f,lz=-1.0f;

// XZ position of the camera
float x=0.0f, z=5.0f;

// the key states. These variables will be zero
//when no key is being presses
float deltaAngle = 0.0f;
float deltaMove = 0;
int xOrigin = -1;

// Constant definitions for Menus
#define RED 1
#define GREEN 2
#define BLUE 3
#define ORANGE 4

#define FILL 1
#define LINE 2

#define SHRINK 1
#define NORMAL 2

// Pop up menu identifiers
int fillMenu, shrinkMenu, mainMenu, colorMenu;

// color for the nose
float red = 1.0f, blue=0.5f, green=0.5f;

// scale of snowman
float scale = 1.0f;

// menu status
int menuFlag = 0;

void changeSize(int w, int h) {

    // Prevent a divide by zero, when window is too short
    // (you cant make a window of zero width).
    if (h == 0)
        h = 1;

    float ratio =  w * 1.0 / h;

    // Use the Projection Matrix
    glMatrixMode(GL_PROJECTION);

    // Reset Matrix
    glLoadIdentity();

    // Set the viewport to be the entire window
    glViewport(0, 0, w, h);

    // Set the correct perspective.
    gluPerspective(45.0f, ratio, 0.1f, 100.0f);

    // Get Back to the Modelview
    glMatrixMode(GL_MODELVIEW);
}

void drawSnowMan() {

    glScalef(scale, scale, scale);
    glColor3f(1.0f, 1.0f, 1.0f);

// Draw Body
    glTranslatef(0.0f ,0.75f, 0.0f);
    glutSolidSphere(0.75f,20,20);

// Draw Head
    glTranslatef(0.0f, 1.0f, 0.0f);
    glutSolidSphere(0.25f,20,20);

// Draw Eyes
    glPushMatrix();
    glColor3f(0.0f,0.0f,0.0f);
    glTranslatef(0.05f, 0.10f, 0.18f);
    glutSolidSphere(0.05f,10,10);
    glTranslatef(-0.1f, 0.0f, 0.0f);
    glutSolidSphere(0.05f,10,10);
    glPopMatrix();

// Draw Nose
    glColor3f(red, green, blue);
    glRotatef(0.0f,1.0f, 0.0f, 0.0f);
    glutSolidCone(0.08f,0.5f,10,2);

    glColor3f(1.0f, 1.0f, 1.0f);
}

void computePos(float deltaMove) {

    x += deltaMove * lx * 0.1f;
    z += deltaMove * lz * 0.1f;
}

void renderScene(void) {

    if (deltaMove)
        computePos(deltaMove);

    // Clear Color and Depth Buffers
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    // Reset transformations
    glLoadIdentity();
    // Set the camera
    gluLookAt(    x, 1.0f, z,
            x+lx, 1.0f,  z+lz,
            0.0f, 1.0f,  0.0f);

// Draw ground

    glColor3f(0.9f, 0.9f, 0.9f);
    glBegin(GL_QUADS);
        glVertex3f(-100.0f, 0.0f, -100.0f);
        glVertex3f(-100.0f, 0.0f,  100.0f);
        glVertex3f( 100.0f, 0.0f,  100.0f);
        glVertex3f( 100.0f, 0.0f, -100.0f);
    glEnd();

// Draw 36 SnowMen

    for(int i = -3; i < 3; i++)
        for(int j=-3; j < 3; j++) {
            glPushMatrix();
            glTranslatef(i*10.0f, 0.0f, j * 10.0f);
            drawSnowMan();
            glPopMatrix();
        }
    glutSwapBuffers();
}

// -----------------------------------
//             KEYBOARD
// -----------------------------------

void processNormalKeys(unsigned char key, int xx, int yy) {

    glutSetMenu(mainMenu);
    switch (key) {
        case 27:
            glutDestroyMenu(mainMenu);
            glutDestroyMenu(fillMenu);
            glutDestroyMenu(colorMenu);
            glutDestroyMenu(shrinkMenu);
            exit(0);
            break;

        case 's':
            if (!menuFlag)
              glutChangeToSubMenu(2,"Shrink",shrinkMenu);
            break;
        case 'c':
            if (!menuFlag)
                glutChangeToSubMenu(2,"Color",colorMenu);
            break;
    }
    if (key == 27)
        exit(0);
}

void pressKey(int key, int xx, int yy) {

    switch (key) {
        case GLUT_KEY_UP : deltaMove = 0.5f; break;
        case GLUT_KEY_DOWN : deltaMove = -0.5f; break;
    }
}

void releaseKey(int key, int x, int y) {

    switch (key) {
        case GLUT_KEY_UP :
        case GLUT_KEY_DOWN : deltaMove = 0;break;
    }
}

// -----------------------------------
//             MOUSE
// -----------------------------------

void mouseMove(int x, int y) {

    // this will only be true when the left button is down
    if (xOrigin >= 0) {

        // update deltaAngle
        deltaAngle = (x - xOrigin) * 0.001f;

        // update camera's direction
        lx = sin(angle + deltaAngle);
        lz = -cos(angle + deltaAngle);
    }
}

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

    // only start motion if the left button is pressed
    if (button == GLUT_LEFT_BUTTON) {

        // when the button is released
        if (state == GLUT_UP) {
            angle += deltaAngle;
            xOrigin = -1;
        }
        else  {// state = GLUT_DOWN
            xOrigin = x;
        }
    }
}

// -----------------------------------
//             MENUS
// -----------------------------------

void processMenuStatus(int status, int x, int y) {

    if (status == GLUT_MENU_IN_USE)
        menuFlag = 1;
    else
        menuFlag = 0;
}

void processMainMenu(int option) {

    // nothing to do in here
    // all actions are for submenus
}

void processFillMenu(int option) {

    switch (option) {

        case FILL: glPolygonMode(GL_FRONT, GL_FILL); break;
        case LINE: glPolygonMode(GL_FRONT, GL_LINE); break;
    }
}

void processShrinkMenu(int option) {

    switch (option) {

        case SHRINK: scale = 0.5f; break;
        case NORMAL: scale = 1.0f; break;
    }
}

void processColorMenu(int option) {

    switch (option) {
        case RED :
            red = 1.0f;
            green = 0.0f;
            blue = 0.0f; break;
        case GREEN :
            red = 0.0f;
            green = 1.0f;
            blue = 0.0f; break;
        case BLUE :
            red = 0.0f;
            green = 0.0f;
            blue = 1.0f; break;
        case ORANGE :
            red = 1.0f;
            green = 0.5f;
            blue = 0.5f; break;
    }
}

void createPopupMenus() {

    shrinkMenu = glutCreateMenu(processShrinkMenu);

    glutAddMenuEntry("Shrink",SHRINK);
    glutAddMenuEntry("NORMAL",NORMAL);

    fillMenu = glutCreateMenu(processFillMenu);

    glutAddMenuEntry("Fill",FILL);
    glutAddMenuEntry("Line",LINE);

    colorMenu = glutCreateMenu(processColorMenu);
    glutAddMenuEntry("Red",RED);
    glutAddMenuEntry("Blue",BLUE);
    glutAddMenuEntry("Green",GREEN);
    glutAddMenuEntry("Orange",ORANGE);

    mainMenu = glutCreateMenu(processMainMenu);

    glutAddSubMenu("Polygon Mode", fillMenu);
    glutAddSubMenu("Color", colorMenu);
    // attach the menu to the right button
    glutAttachMenu(GLUT_RIGHT_BUTTON);

    // this will allow us to know if the menu is active
    glutMenuStatusFunc(processMenuStatus);
}

// -----------------------------------
//             MAIN
// -----------------------------------

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

    // init GLUT and create window
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
    glutInitWindowPosition(100,100);
    glutInitWindowSize(320,320);
    glutCreateWindow("Lighthouse3D - GLUT Tutorial");

    // register callbacks
    glutDisplayFunc(renderScene);
    glutReshapeFunc(changeSize);
    glutIdleFunc(renderScene);

    glutIgnoreKeyRepeat(1);
    glutKeyboardFunc(processNormalKeys);
    glutSpecialFunc(pressKey);
    glutSpecialUpFunc(releaseKey);

    // here are the two new functions
    glutMouseFunc(mouseButton);
    glutMotionFunc(mouseMove);

    // OpenGL init
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);

    // init Menus
    createPopupMenus();

    // enter GLUT event processing cycle
    glutMainLoop();

    return 1;
}