OpenGL使用glColorMaterial设置材质



OpenGL使用glColorMaterial设置材质  


一句话glColorMaterial的作用是用来在绘图的过程中实时的设置材质。通常情况下设置一个物体的材质需要以下这么5个属性需要设置。

  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);
除了采用glMaterialfv()设置材质外,还可以使用glColorMaterial()设置材质属性。

void glColorMaterial(GLenum face,GLenum mode)来实现。
face的取值: GL_FRONT GL_BACK GL_FRONT_AND_BACK
mode的取值: GL_AMBIENT GL_DIFFUSE GL_AMBIENT_AND_DIFFUSE GL_SPECULAR GL_EMISSION
在想要使用这个函数时,要启用glEnable(GL_COLOR_MATERIAL)来是函数工作。
在绘图时使用glColor*()来实时改变材质颜色,或用glMaterial()来实时改变材质成分
使用完毕,要用glDisable(GL_COLOR_MATERIAL)来关闭这种材质模式。

例如:
glColorMaterial(GL_FRONT,GL_DIFFUSE);
glEnable(GL_COLOR_MATERIAL);

glColor3f(0.3,0.5,0.7);
//画一些物体:
...

glColor3f(0.0,1.0,0.0);
//再画另一些物体:
...

glDisable(GL_COLOR_MATERIAL);

说明:
当需要改变场景中大部分方面的单个材质时,最好调用glColorMaterial()
当修改不只一个材质参数,最好调用glMaterial*(),这是目前我体会到唯一的使用功能上的不同点吧。

void glColorMaterial(GLenum face, GLenum mode); Causes the material property (or properties) specified by mode of the specified material face (or faces) specified by face to track the value of the current color at all times. A change to the current color (using glColor*()) immediately updates the specified material properties.The face parameter can be GL_FRONT, GL_BACK, or GL_FRONT_AND_BACK (the default). The mode parameter can be GL_AMBIENT, GL_DIFFUSE, GL_AMBIENT_AND_DIFFUSE (the default), GL_SPECULAR, or GL_EMISSION. At any given time, only one mode is active.glColorMaterial() has no effect on color-index lighting.

After calling glColorMaterial(), you need to call glEnable() with GL_COLOR_MATERIAL as the parameter. Then, you can change the current color usingglColor*() (or other material properties, using glMaterial*()) as needed as you draw:

glEnable(GL_COLOR_MATERIAL);
glColorMaterial(GL_FRONT, GL_DIFFUSE);
/* now glColor* changes diffuse reflection  */
glColor3f(0.2, 0.5, 0.8);
/* draw some objects here */
glColorMaterial(GL_FRONT, GL_SPECULAR);
/* glColor* no longer changes diffuse reflection  */
/* now glColor* changes specular reflection  */
glColor3f(0.9, 0.0, 0.2);
/* draw other objects here */
glDisable(GL_COLOR_MATERIAL);

You should use glColorMaterial() whenever you need to change a single material parameterfor most vertices in your scene. If you need to change more than one material parameter, as was the case for"Plate 16" in Appendix I, use glMaterial*(). When you don't need the capabilities ofglColorMaterial() anymore, be sure to disable it so that you don't get undesired material properties and don't incur the performance cost associated with it.

例:采用鼠标的左中右键实时设置物体材质的颜色
/* an interactive program that uses glColorMaterial() to change material parameters. Pressing each of the three mouse buttons changes the color of the diffuse reflection. */

#include
#include

GLfloat diffuseMaterial[4] = { 0.5, 0.5, 0.5, 1.0 };

void init(void)
{
   GLfloat mat_specular[] = { 1.0, 1.0, 1.0, 1.0 };
   GLfloat light_position[] = { 1.0, 1.0, 1.0, 0.0 };

   glClearColor (0.0, 0.0, 0.0, 0.0);
   glShadeModel (GL_SMOOTH);
   glEnable(GL_DEPTH_TEST);
   glMaterialfv(GL_FRONT, GL_DIFFUSE, diffuseMaterial);
   glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
   glMaterialf(GL_FRONT, GL_SHININESS, 25.0);
   glLightfv(GL_LIGHT0, GL_POSITION, light_position);
   glEnable(GL_LIGHTING);
   glEnable(GL_LIGHT0);

   glColorMaterial(GL_FRONT, GL_DIFFUSE);
   glEnable(GL_COLOR_MATERIAL);
}

void display(void)
{
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   glutSolidSphere(1.0, 20, 16);
   glFlush ();
}

void reshape (int w, int h)
{
   glViewport (0, 0, (GLsizei) w, (GLsizei) h);
   glMatrixMode (GL_PROJECTION);
   glLoadIdentity();
   if (w <= h)
      glOrtho (-1.5, 1.5, -1.5*(GLfloat)h/(GLfloat)w,
         1.5*(GLfloat)h/(GLfloat)w, -10.0, 10.0);
   else
      glOrtho (-1.5*(GLfloat)w/(GLfloat)h,
         1.5*(GLfloat)w/(GLfloat)h, -1.5, 1.5, -10.0, 10.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
}

void mouse(int button, int state, int x, int y)
{
   switch (button) {
      case GLUT_LEFT_BUTTON:
         if (state == GLUT_DOWN) {
            diffuseMaterial[0] += 0.1;
            if (diffuseMaterial[0] > 1.0)
               diffuseMaterial[0] = 0.0;
            glColor4fv(diffuseMaterial);
            glutPostRedisplay();
         }
         break;
      case GLUT_MIDDLE_BUTTON:
         if (state == GLUT_DOWN) {
            diffuseMaterial[1] += 0.1;
            if (diffuseMaterial[1] > 1.0)
               diffuseMaterial[1] = 0.0;
            glColor4fv(diffuseMaterial);
            glutPostRedisplay();
         }
         break;
      case GLUT_RIGHT_BUTTON:
         if (state == GLUT_DOWN) {
            diffuseMaterial[2] += 0.1;
            if (diffuseMaterial[2] > 1.0)
               diffuseMaterial[2] = 0.0;
            glColor4fv(diffuseMaterial);
            glutPostRedisplay();
         }
         break;
      default:
         break;
   }
}

void keyboard(unsigned char key, int x, int y)
{
   switch (key) {
      case 27:
         exit(0);
         break;
   }
}

int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
   glutInitWindowSize (500, 500);
   glutInitWindowPosition (100, 100);
   glutCreateWindow (argv[0]);
   init ();
   glutDisplayFunc(display);
   glutReshapeFunc(reshape);
   glutMouseFunc(mouse);
   glutKeyboardFunc(keyboard);
   glutMainLoop();
   return 0;
}

还在学习,转载自http://anony3721.blog.163.com/blog/static/511974201141345834693/

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