OpenGL 点参数 示例

#include <GL/glut.h>
#include <gl/glext.h>
#include <stdlib.h>
#include <stdio.h>

#define GL_DISTANCE_ATTENUATION_EXT 0x8129
#define GL_POINT_FADE_THRESHOLD_SIZE_EXT 0x8128
#define GL_POINT_SIZE_MIN_EXT 0x8126
#define GL_POINT_SIZE_MAX_EXT 0x8127

#define GL_POINT_FADE_THRESHOLD_SIZE_ARB  0x8128
#define GL_POINT_DISTANCE_ATTENUATION_ARB 0x8129

static GLfloat linearsize = 0.1;
static GLfloat psize = 7.0;
static GLfloat pmax;
static GLfloat constant[3] = {1.0, 0.0, 0.0};
static GLfloat linear[3] = {0.0, 0.12, 0.0};
static GLfloat quadratic[3] = {0.0, 0.0, 0.01};

PFNGLPOINTPARAMETERFARBPROC glPointParameterfEXT;
PFNGLPOINTPARAMETERFVARBPROC glPointParameterfvEXT;

void init(void) 
{
    glPointParameterfEXT = (PFNGLPOINTPARAMETERFARBPROC)wglGetProcAddress("glPointParameterfARB");
    glPointParameterfvEXT = (PFNGLPOINTPARAMETERFVARBPROC)wglGetProcAddress("glPointParameterfvARB");

    int i;
   srand (12345);
   glNewList(1, GL_COMPILE);
   glBegin (GL_POINTS);
      for (i = 0; i < 250; i++) {
          glColor3f (1.0, ((rand()/(float) RAND_MAX) * 0.5) + 0.5, rand()/(float) RAND_MAX);
/*  randomly generated vertices:
    -5 < x < 5;  -5 < y < 5;  -5 < z < -45  */
          glVertex3f ( ((rand()/(float)RAND_MAX) * 10.0) - 5.0, 
                       ((rand()/(float)RAND_MAX) * 10.0) - 5.0, 
                       ((rand()/(float)RAND_MAX) * 40.0) - 45.0); 
      }
   glEnd();
   glEndList();

   glEnable(GL_DEPTH_TEST);
   glEnable(GL_POINT_SMOOTH);
   glEnable(GL_BLEND);
   glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); 
   glPointSize(psize);
   glGetFloatv(GL_POINT_SIZE_MAX_EXT, &pmax);

   glPointParameterfvEXT(GL_DISTANCE_ATTENUATION_EXT, linear);
   glPointParameterfEXT(GL_POINT_FADE_THRESHOLD_SIZE_EXT, 2.0);
}

void display(void)
{
   glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   glCallList (1);
   glutSwapBuffers ();
}

void reshape (int w, int h)
{
   glViewport (0, 0, (GLsizei) w, (GLsizei) h);
   glMatrixMode (GL_PROJECTION);
   glLoadIdentity ();
   gluPerspective (35.0, 1.0, 0.25, 200.0);
   glMatrixMode (GL_MODELVIEW);
   glTranslatef (0.0, 0.0, -10.0);
}

void keyboard(unsigned char key, int x, int y)
{
   switch (key) {
      case 'b':
            glMatrixMode (GL_MODELVIEW);
            glTranslatef (0.0, 0.0, -0.5);
            glutPostRedisplay();
         break;
      case 'c':
            glPointParameterfvEXT(GL_DISTANCE_ATTENUATION_EXT, constant);
            glutPostRedisplay();
         break;
      case 'f':
            glMatrixMode (GL_MODELVIEW);
            glTranslatef (0.0, 0.0, 0.5);
            glutPostRedisplay();
         break;
      case 'l':
            glPointParameterfvEXT (GL_DISTANCE_ATTENUATION_EXT, linear);
            glutPostRedisplay();
         break;
      case 'q':
            glPointParameterfvEXT (GL_DISTANCE_ATTENUATION_EXT, quadratic);
            glutPostRedisplay();
         break;
      case '+':
            if (psize < (pmax + 1.0))
               psize = psize + 1.0;
            glPointSize(psize);
            glutPostRedisplay();
         break;
      case '-':
            if (psize >= 2.0)
               psize = psize - 1.0;
            glPointSize(psize);
            glutPostRedisplay();
         break;
      case 27:
         exit(0);
         break;
   }
}

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

书中给出的代码运行报错，这是我查了很多资料之后自己改写的，可以运行。运行效果如下：

1. quadratic

2.constant

3.linear