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 byface 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 <GL/glut.h>
#include <stdlib.h>

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/