/* Using fog in a scene.

Written by Caroline Geiersbach and Scott D. Anderson
scott.anderson@acm.org
Summer 2003
*/

#include <stdio.h>
#include <math.h>
#include <GL/glut.h>
#include <tw.h>

int FogOption = 0;

void fog() {
  glEnable(GL_FOG);
  GLfloat fogColor[4]={0.3,0.3,0.3,1};
  glFogfv(GL_FOG_COLOR,fogColor);
  glHint(GL_FOG_HINT,GL_NICEST);
  switch(FogOption) {
  case 0:
    printf("No Fog\n");
    glDisable(GL_FOG);
    break;
  case 1: 
    printf("Linear Fog\n");
    glFogi(GL_FOG_MODE, GL_LINEAR);
    glFogf(GL_FOG_START, 10);
    glFogf(GL_FOG_END, 60);
    break;
  case 2:
    printf("Exponential Decay Fog\n");
    glFogi(GL_FOG_MODE, GL_EXP);
    glFogf(GL_FOG_DENSITY, 0.01);
    break;
  case 3:
    printf("Gaussian Decay Fog\n");
    glFogi(GL_FOG_MODE, GL_EXP2);
    glFogf(GL_FOG_DENSITY, 0.01);
    break;
  }
}

void display(void) {
    int i;
    twDisplayInit(0.3,0.3,0.3);
    twCamera();
    fog();

    twColorName(TW_GREEN);
    twGround();

    twColorName(TW_MAGENTA);
    glPushMatrix();
    glTranslatef(50,0,50);
    glScalef(1,40,1);                // for tall cubes
    for(int i=0; i<50; i++) {
      glutSolidCube(0.5);
      glTranslatef(-1,0,-1);
    }
    glPopMatrix();

    glFlush();
    glutSwapBuffers();
}

void fogToggle(unsigned char k, int, int) {
  FogOption = (FogOption+1)%4;
  glutPostRedisplay();
}

int main(int argc, char** argv) {
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
  twInitWindowSize(500,500);
  glutCreateWindow(argv[0]);
  glutDisplayFunc(display);
  twBoundingBox(0,50,0,20,0,50);
  twMainInit(); 
  twKeyCallback('f',fogToggle,"switch among fog options");
  glutMainLoop();
  return 0;
}