OpenGL超级宝典学习笔记——光照参数与材料属性

//明亮的白光
GLfloat ambientLight[] = {1.0f, 1.0f, 1.0f, 1.0f};
//开启光照
glEnable(GL_LIGHTING);
//设置全局环境光为白光
glLightModelfv(GL_LIGHT_MODEL_AMBIENT, ambientLight);

 

全局环境光照的默认RGBA值是(0.2, 0.2, 0.2, 1.0)，这个值是比较昏暗的。

 

//灰色的材料属性
GLfloat gray[] = {0.75f, 0.75f, 0.75f, 1.0f};

glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, gray);
glBegin(GL_TRIANGLES);
    glVertex3f(-15.0f, 0.0f, 30.0f);
    glVertex3f(0.0f, 15.0f, 30.0f);
    glVertex3f(0.0f, 0.0f, -56.0f);
glEnd();

glMaterialfv的第一个参数是指定正面, 反面, 正面和反面。第二个参数是告诉Opengl设置哪个属性。GL_AMBIENT_AND_DIFFUSE指定环境光反射属性和漫反射属性为同一个值。最后一个参数是一个RGBA值的数组。

在绝大多数情况下，环境光和漫反射光的成分是相同的，除非需要特殊的镜面光的效果。在多边形顶点之前需要调用glMaterial函数，并设置一个包含各种颜色成分的数组。这个操作还是相当繁琐的。下面介绍一种更简单的方式

 

第二种方法颜色追踪较为简单。使用颜色追踪，可以通过glColor来设置材料属性。第一步启用颜色追踪

glEnable(GL_COLOR_MATERIAL);

然后通过glColorMaterial指定需要颜色追踪的材料属性。下面的例子的设置 追踪多边形正面的环境光和漫反射的材料属性。

glColorMaterial(GL_FRONT, GL_AMBIENT_ANDDIFFUSE);

 

下面的例子使用颜色追踪的方式重写上面的例子：

//开启颜色追踪
glEnable(GL_COLOR_MATERIAL);
//设置颜色追踪的材料属性以及多边形的面
glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);

//设置颜色
glColor3f(0.75f, 0.75f, 0.75f);
glBegin(GL_TRIANGLES);
    glVertex3f(-15.0f, 0.0f, 30.0f);
    glVertex3f(0.0f, 15.0f, 30.0f);
    glVertex3f(0.0f, 0.0f, -56.0f);
glEnd();

设置环境的例子:

void SetupRC()
{
  GLfloat ambientLight[] = {1.0f, 1.0f, 1.0f, 1.0f};
  glEnable(GL_DEPTH_TEST);    
  glEnable(GL_CULL_FACE);       
  glFrontFace(GL_CCW);        

  glEnable(GL_COLOR_MATERIAL);
  glEnable(GL_LIGHTING);
  //设置光照模型
  glLightModelfv(GL_LIGHT_MODEL_AMBIENT, ambientLight);
  //设置材料追踪
  glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);


  glClearColor(0.0f, 0.0f, 05.f,1.0f);
}

开启明亮的环境光效果:

 

把环境光调成原来的一半的效果:

GLfloat ambientLight[] = {0.5f, 0.5f, 0.5f, 1.0f};

完整的例子：
#include "gltools.h"    // System and OpenGL Stuff


// Rotation amounts
static GLfloat xRot = 0.0f;
static GLfloat yRot = 0.0f;


// Called to draw scene
void RenderScene(void)
{
// Clear the window with current clearing color
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

// Save matrix state and do the rotation
  glPushMatrix();
    glRotatef(xRot, 1.0f, 0.0f, 0.0f);
    glRotatef(yRot, 0.0f, 1.0f, 0.0f);

    glColor3f(1.0f, 1.0f, 1.0f);
    glBegin(GL_TRIANGLES);
//机头
      glVertex3f(-15.0f, 0.0f, 30.0f);
      glVertex3f(15.0f, 0.0f, 30.0f);
      glVertex3f(0.0f, 0.0f, 60.0f);

      glColor3f(0.0f, 0.0f, 0.0f);
      glVertex3f(-15.0f, 0.0f, 30.0f);
      glVertex3f(0.0f, 0.0f, 60.0f);
      glVertex3f(0.0f, 15.0f, 30.0f);

      glColor3f(1.0f, 0.0f, 0.0f);
      glVertex3f(0.0f, 0.0f, 60.0f);
      glVertex3f(15.0f, 0.0f, 30.0f);
      glVertex3f(0.0f, 15.0f, 30.0f);
//机身
      glColor3f(0.0f, 1.0f, 0.0f);
      glVertex3f(-15.0f, 0.0f, 30.0f);
      glVertex3f(0.0f, 15.0f, 30.0f);
      glVertex3f(0.0f, 0.0f, -53.0f);

      glColor3f(1.0f, 1.0f, 0.0f);
      glVertex3f(0.0f, 15.0f, 30.0f);
      glVertex3f(15.0f, 0.0f, 30.0f);
      glVertex3f(0.0f, 0.0f, -53.0f);

      glColor3f(0.5f, 0.5f, 0.3f);
      glVertex3f(15.0f, 0.0f, 30.0f);
      glVertex3f(-15.0f, 0.0f, 30.0f);
      glVertex3f(0.0f, 0.0f, -53.0f);

//机尾巴
      glColor3f(0.3f, 1.0f, 0.2f);
      glVertex3f(0.0f, 0.0f, -53.0f);
      glVertex3f(0.0f, 0.0f, -70.0f);
      glVertex3f(0.0f, 15.0f, -70.0f);

      glColor3f(0.7f, 0.5f, 0.3f);
      glVertex3f(-15.0f, 0.0f, -70.0f);
      glVertex3f(0.0f, 0.0f, -53.0f);
      glVertex3f(0.0f, 0.0f, -70.0f);

      glColor3f(0.2f, 0.2f, 0.8f);
      glVertex3f(15.0f, 0.0f, -70.0f);
      glVertex3f(0.0f, 0.0f, -70.0f);
      glVertex3f(0.0f, 0.0f, -53.0f);

//由于背面被消除，背面再画一次
      glColor3f(0.3f, 1.0f, 0.2f);
      glVertex3f(0.0f, 0.0f, -70.0f);
      glVertex3f(0.0f, 0.0f, -53.0f);
      glVertex3f(0.0f, 15.0f, -70.0f);


      glColor3f(0.7f, 0.5f, 0.3f);
      glVertex3f(0.0f, 0.0f, -53.0f);
      glVertex3f(-15.0f, 0.0f, -70.0f);
      glVertex3f(0.0f, 0.0f, -70.0f);

      glColor3f(0.2f, 0.2f, 0.8f);
      glVertex3f(0.0f, 0.0f, -70.0f);
      glVertex3f(15.0f, 0.0f, -70.0f);
      glVertex3f(0.0f, 0.0f, -53.0f);

// 左翼 
      glColor3ub(128,128,128);
      glVertex3f(0.0f,2.0f,27.0f);
      glVertex3f(-60.0f, 2.0f, -8.0f);
      glVertex3f(60.0f, 2.0f, -8.0f);

      glColor3ub(64,64,64);
      glVertex3f(60.0f, 2.0f, -8.0f);
      glVertex3f(0.0f, 7.0f, -8.0f);
      glVertex3f(0.0f,2.0f,27.0f);

      glColor3ub(192,192,192);
      glVertex3f(60.0f, 2.0f, -8.0f);
      glVertex3f(-60.0f, 2.0f, -8.0f);
      glVertex3f(0.0f,7.0f,-8.0f);

//右翼 
      glColor3ub(64,64,64);
      glVertex3f(0.0f,2.0f,27.0f);
      glVertex3f(0.0f, 7.0f, -8.0f);
      glVertex3f(-60.0f, 2.0f, -8.0f);
    glEnd();
  glPopMatrix();

// Display the results
  glutSwapBuffers();
}

// This function does any needed initialization on the rendering
// context. 
void SetupRC()
{
  GLfloat ambientLight[] = {0.5f, 0.5f, 0.5f, 1.0f};
  glEnable(GL_DEPTH_TEST);    // Hidden surface removal
  glEnable(GL_CULL_FACE);        // Do not calculate inside of jet
  glFrontFace(GL_CCW);        // Counter clock-wise polygons face out

  glEnable(GL_COLOR_MATERIAL);
  glEnable(GL_LIGHTING);

  glLightModelfv(GL_LIGHT_MODEL_AMBIENT, ambientLight);

  glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);

// Nice light blue
  glClearColor(0.0f, 0.0f, 05.f,1.0f);
}

void SpecialKeys(int key, int x, int y)
{
if(key == GLUT_KEY_UP)
    xRot-= 5.0f;

if(key == GLUT_KEY_DOWN)
    xRot += 5.0f;

if(key == GLUT_KEY_LEFT)
    yRot -= 5.0f;

if(key == GLUT_KEY_RIGHT)
    yRot += 5.0f;

if(key > 356.0f)
    xRot = 0.0f;

if(key < -1.0f)
    xRot = 355.0f;

if(key > 356.0f)
    yRot = 0.0f;

if(key < -1.0f)
    yRot = 355.0f;

// Refresh the Window
  glutPostRedisplay();
}


void ChangeSize(int w, int h)
{
  GLfloat nRange = 80.0f;
// Prevent a divide by zero
if(h == 0)
    h = 1;

// Set Viewport to window dimensions
  glViewport(0, 0, w, h);

// Reset coordinate system
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();

// Establish clipping volume (left, right, bottom, top, near, far)
if (w <= h) 
    glOrtho (-nRange, nRange, -nRange*h/w, nRange*h/w, -nRange, nRange);
else 
    glOrtho (-nRange*w/h, nRange*w/h, -nRange, nRange, -nRange, nRange);

  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
}

int main(int argc, char* argv[])
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
  glutInitWindowSize(800,600);
  glutCreateWindow("Jet");
  glutReshapeFunc(ChangeSize);
  glutSpecialFunc(SpecialKeys);
  glutDisplayFunc(RenderScene);
  SetupRC();
  glutMainLoop();

return 0;
}