OpenGL中光照的设置

发表于 分类于 阅读次数： Waline：
本文详细介绍OpenGL光照编程的核心步骤。首先定义光源的颜色和位置，创建GL_LIGHT1光源，设置环境光、漫射光和光源位置。接着配置光照模型，通过glLightModelfv设置全局环境光和局部观察者。然后定义材质属性，包括无材质、环境色、漫射色、镜面反射色、光泽度和自发光值。最后绘制多个球体演示不同材质组合效果，包括仅漫射反射、漫射加镜面反射不同光泽度、添加自发光等。每种组合通过变换矩阵定位

1.创建、定位和启用光源

（1）定义光源的颜色和位置

GLfloat ambient[] = { 0.0, 0.0, 0.0, 1.0 };
GLfloat diffuse[] = { 1.0, 1.0, 1.0, 1.0 };
GLfloat position[] = { 0.0, 3.0, 2.0, 0.0 };

（2）创建光源

glLightfv(GL_LIGHT1, GL_AMBIENT, ambient);  // Setup The Ambient Light设置环境光
glLightfv(GL_LIGHT1, GL_DIFFUSE, diffuse);  // Setup The Diffuse Light设置漫射光
glLightfv(GL_LIGHT1, GL_POSITION, position);  // Position The Light设置光源位置

（3）启动光照和光源

glEnable(GL_LIGHTING);     // 启动光照
glEnable(GL_LIGHT1);     // Enable Light One启用一号光源

2.选择光照模型

GLfloat lmodel_ambient[] = { 0.4, 0.4, 0.4, 1.0 };
GLfloat local_view[] = { 0.0 };

glLightModelfv(GL_LIGHT_MODEL_AMBIENT, lmodel_ambient);
glLightModelfv(GL_LIGHT_MODEL_LOCAL_VIEWER, local_view);

3.定义材质

（1）材料属性

GLfloat no_mat[] = { 0.0, 0.0, 0.0, 1.0 };
GLfloat mat_ambient[] = { 0.7, 0.7, 0.7, 1.0 };
GLfloat mat_ambient_color[] = { 0.8, 0.8, 0.2, 1.0 };
GLfloat mat_diffuse[] = { 0.1, 0.5, 0.8, 1.0 };
GLfloat mat_specular[] = { 1.0, 1.0, 1.0, 1.0 };
GLfloat no_shininess[] = { 0.0 };
GLfloat low_shininess[] = { 5.0 };
GLfloat high_shininess[] = { 100.0 };
GLfloat mat_emission[] = { 0.3, 0.2, 0.2, 0.0 };

（2）指定材料属性

glMaterialfv(GL_FRONT, GL_AMBIENT, no_mat);
glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
glMaterialfv(GL_FRONT, GL_SPECULAR, no_mat);
glMaterialfv(GL_FRONT, GL_SHININESS, no_shininess);
glMaterialfv(GL_FRONT, GL_EMISSION, no_mat);

4.绘制物体

glutSolidSphere(1.0, 16, 16);

引用 OpenGL 编程指南中的例子：

void init(void)
{
    GLfloat ambient[] = { 0.0, 0.0, 0.0, 1.0 };
    GLfloat diffuse[] = { 1.0, 1.0, 1.0, 1.0 };
    GLfloat position[] = { 0.0, 3.0, 2.0, 0.0 };
    GLfloat lmodel_ambient[] = { 0.4, 0.4, 0.4, 1.0 };
    GLfloat local_view[] = { 0.0 };

    glClearColor(0.0, 0.1, 0.1, 0.0);
    glEnable(GL_DEPTH_TEST);
    glShadeModel(GL_SMOOTH);
    glLightfv(GL_LIGHT0, GL_AMBIENT, ambient);
    glLightfv(GL_LIGHT0, GL_DIFFUSE, diffuse);
    glLightfv(GL_LIGHT0, GL_POSITION, position);
    glLightModelfv(GL_LIGHT_MODEL_AMBIENT, lmodel_ambient);
    glLightModelfv(GL_LIGHT_MODEL_LOCAL_VIEWER, local_view);
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
}
void display(void)
{
    GLfloat no_mat[] = { 0.0, 0.0, 0.0, 1.0 };
    GLfloat mat_ambient[] = { 0.7, 0.7, 0.7, 1.0 };
    GLfloat mat_ambient_color[] = { 0.8, 0.8, 0.2, 1.0 };
    GLfloat mat_diffuse[] = { 0.1, 0.5, 0.8, 1.0 };
    GLfloat mat_specular[] = { 1.0, 1.0, 1.0, 1.0 };
    GLfloat no_shininess[] = { 0.0 };
    GLfloat low_shininess[] = { 5.0 };
    GLfloat high_shininess[] = { 100.0 };
    GLfloat mat_emission[] = { 0.3, 0.2, 0.2, 0.0 };

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    /* draw sphere in first row, first column
     *  diffuse reflection only; no ambient or specular
     */
    glPushMatrix();
    glTranslatef(-3.75, 3.0, 0.0);
    glMaterialfv(GL_FRONT, GL_AMBIENT, no_mat);
    glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
    glMaterialfv(GL_FRONT, GL_SPECULAR, no_mat);
    glMaterialfv(GL_FRONT, GL_SHININESS, no_shininess);
    glMaterialfv(GL_FRONT, GL_EMISSION, no_mat);
    glutSolidSphere(1.0, 16, 16);
    glPopMatrix();

    /* draw sphere in first row, second column
     *  diffuse and specular reflection; low shininess; no ambient
     */
    glPushMatrix();
    glTranslatef(-1.25, 3.0, 0.0);
    glMaterialfv(GL_FRONT, GL_AMBIENT, no_mat);
    glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
    glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
    glMaterialfv(GL_FRONT, GL_SHININESS, low_shininess);
    glMaterialfv(GL_FRONT, GL_EMISSION, no_mat);
    glutSolidSphere(1.0, 16, 16);
    glPopMatrix();

    /* draw sphere in first row, third column
     *  diffuse and specular reflection; high shininess; no ambient
     */
    glPushMatrix();
    glTranslatef(1.25, 3.0, 0.0);
    glMaterialfv(GL_FRONT, GL_AMBIENT, no_mat);
    glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
    glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
    glMaterialfv(GL_FRONT, GL_SHININESS, high_shininess);
    glMaterialfv(GL_FRONT, GL_EMISSION, no_mat);
    glutSolidSphere(1.0, 16, 16);
    glPopMatrix();

    /* draw sphere in first row, fourth column
     *  diffuse reflection; emission; no ambient or specular reflection
     */
    glPushMatrix();
    glTranslatef(3.75, 3.0, 0.0);
    glMaterialfv(GL_FRONT, GL_AMBIENT, no_mat);
    glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
    glMaterialfv(GL_FRONT, GL_SPECULAR, no_mat);
    glMaterialfv(GL_FRONT, GL_SHININESS, no_shininess);
    glMaterialfv(GL_FRONT, GL_EMISSION, mat_emission);
    glutSolidSphere(1.0, 16, 16);
    glPopMatrix();

    /* draw sphere in second row, first column
     *  ambient and diffuse reflection; no specular
     */
    glPushMatrix();
    glTranslatef(-3.75, 0.0, 0.0);
    glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient);
    glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
    glMaterialfv(GL_FRONT, GL_SPECULAR, no_mat);
    glMaterialfv(GL_FRONT, GL_SHININESS, no_shininess);
    glMaterialfv(GL_FRONT, GL_EMISSION, no_mat);
    glutSolidSphere(1.0, 16, 16);
    glPopMatrix();

    /* draw sphere in second row, second column
     *  ambient, diffuse and specular reflection; low shininess
     */
    glPushMatrix();
    glTranslatef(-1.25, 0.0, 0.0);
    glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient);
    glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
    glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
    glMaterialfv(GL_FRONT, GL_SHININESS, low_shininess);
    glMaterialfv(GL_FRONT, GL_EMISSION, no_mat);
    glutSolidSphere(1.0, 16, 16);
    glPopMatrix();

    /* draw sphere in second row, third column
     *  ambient, diffuse and specular reflection; high shininess
     */
    glPushMatrix();
    glTranslatef(1.25, 0.0, 0.0);
    glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient);
    glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
    glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
    glMaterialfv(GL_FRONT, GL_SHININESS, high_shininess);
    glMaterialfv(GL_FRONT, GL_EMISSION, no_mat);
    glutSolidSphere(1.0, 16, 16);
    glPopMatrix();

    /* draw sphere in second row, fourth column
     *  ambient and diffuse reflection; emission; no specular
     */
    glPushMatrix();
    glTranslatef(3.75, 0.0, 0.0);
    glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient);
    glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
    glMaterialfv(GL_FRONT, GL_SPECULAR, no_mat);
    glMaterialfv(GL_FRONT, GL_SHININESS, no_shininess);
    glMaterialfv(GL_FRONT, GL_EMISSION, mat_emission);
    glutSolidSphere(1.0, 16, 16);
    glPopMatrix();

    /* draw sphere in third row, first column
     *  colored ambient and diffuse reflection; no specular
     */
    glPushMatrix();
    glTranslatef(-3.75, -3.0, 0.0);
    glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient_color);
    glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
    glMaterialfv(GL_FRONT, GL_SPECULAR, no_mat);
    glMaterialfv(GL_FRONT, GL_SHININESS, no_shininess);
    glMaterialfv(GL_FRONT, GL_EMISSION, no_mat);
    glutSolidSphere(1.0, 16, 16);
    glPopMatrix();

    /* draw sphere in third row, second column
     *  colored ambient, diffuse and specular reflection; low shininess
     */
    glPushMatrix();
    glTranslatef(-1.25, -3.0, 0.0);
    glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient_color);
    glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
    glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
    glMaterialfv(GL_FRONT, GL_SHININESS, low_shininess);
    glMaterialfv(GL_FRONT, GL_EMISSION, no_mat);
    glutSolidSphere(1.0, 16, 16);
    glPopMatrix();

    /* draw sphere in third row, third column
     *  colored ambient, diffuse and specular reflection; high shininess
     */
    glPushMatrix();
    glTranslatef(1.25, -3.0, 0.0);
    glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient_color);
    glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
    glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
    glMaterialfv(GL_FRONT, GL_SHININESS, high_shininess);
    glMaterialfv(GL_FRONT, GL_EMISSION, no_mat);
    glutSolidSphere(1.0, 16, 16);
    glPopMatrix();

    /* draw sphere in third row, fourth column
     *  colored ambient and diffuse reflection; emission; no specular
     */
    glPushMatrix();
    glTranslatef(3.75, -3.0, 0.0);
    glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient_color);
    glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
    glMaterialfv(GL_FRONT, GL_SPECULAR, no_mat);
    glMaterialfv(GL_FRONT, GL_SHININESS, no_shininess);
    glMaterialfv(GL_FRONT, GL_EMISSION, mat_emission);
    glutSolidSphere(1.0, 16, 16);
    glPopMatrix();

    glFlush();
}
void reshape(int w, int h)
{
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    if (w <= (h * 2))
        glOrtho(-6.0, 6.0, -3.0 * ((GLfloat)h * 2) / (GLfloat)w,
                3.0 * ((GLfloat)h * 2) / (GLfloat)w, -10.0, 10.0);
    else
        glOrtho(-6.0 * (GLfloat)w / ((GLfloat)h * 2),
                6.0 * (GLfloat)w / ((GLfloat)h * 2), -3.0, 3.0, -10.0, 10.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize(600, 450);
    glutCreateWindow(argv[0]);
    init();
    glutReshapeFunc(reshape);
    glutDisplayFunc(display);
    glutKeyboardFunc(keyboard);
    glutMainLoop();
    return 0;
}

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