
/* Copyright (c) Mark J. Kilgard, 1997.  */

/* This program is freely distributable without licensing fees 
   and is provided without guarantee or warrantee expressed or 
   implied. This program is -not- in the public domain. */

/* This example demonstrates how to render particle effects
   with OpenGL.  A cloud of pinkish/orange particles explodes with the
   particles bouncing off the ground.  When the EXT_point_parameters
   is present , the particle size is attenuated based on eye distance. */


#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>       /* for cos(), sin(), and sqrt() */
#ifdef _WIN32
#include <windows.h>
#endif
#define GL_GLEXT_PROTOTYPES
#include <GL/glut.h>

/* Some <math.h> files do not define M_PI... */
#ifndef M_PI
#define M_PI 3.14159265
#endif

#if 0  /* For debugging. */
#undef GL_EXT_point_parameters
#endif

static GLfloat angle = -150;   /* in degrees */
static int spin = 0;
static int moving, begin;
static int newModel = 1;
static float theTime;
static int repeat = 1;
static int blend = 1;
int useMipmaps = 1;
int linearFiltering = 1;

static GLfloat constant[3] = { 1/5.0, 0.0, 0.0 };
static GLfloat linear[3] = { 0.0, 1/5.0, 0.0 };
static GLfloat theQuad[3] = { 0.25, 0.0, 1/60.0 };

#define MAX_POINTS 2000

static int numPoints = 200;

static GLfloat pointList[MAX_POINTS][3];
static GLfloat pointTime[MAX_POINTS];
static GLfloat pointVelocity[MAX_POINTS][2];
static GLfloat pointDirection[MAX_POINTS][2];
static int colorList[MAX_POINTS];
static int animate = 1, motion = 0;

static GLfloat colorSet[][4] = {
  /* Shades of red. */
  { 0.7, 0.2, 0.4, 0.5 },
  { 0.8, 0.0, 0.7, 0.5 },
  { 1.0, 0.0, 0.0, 0.5 },
  { 0.9, 0.3, 0.6, 0.5 },
  { 1.0, 0.4, 0.0, 0.5 },
  { 1.0, 0.0, 0.5, 0.5 },
};

#define NUM_COLORS (sizeof(colorSet)/sizeof(colorSet[0]))

#define DEAD (NUM_COLORS+1)


#if 0  /* drand48 might be better on Unix machines */
#define RANDOM_RANGE(lo, hi) ((lo) + (hi - lo) * drand48())
#else
static float float_rand(void) { return rand() / (float) RAND_MAX; }
#define RANDOM_RANGE(lo, hi) ((lo) + (hi - lo) * float_rand())
#endif

#define MEAN_VELOCITY 3.0
#define GRAVITY 2.0

/* Modeling units of ground extent in each X and Z direction. */
#define EDGE 12

static void
makePointList(void)
{
  float angle, velocity, direction;
  int i;

  motion = 1;
  for (i=0; i<numPoints; i++) {
    pointList[i][0] = 0.0;
    pointList[i][1] = 0.0;
    pointList[i][2] = 0.0;
    pointTime[i] = 0.0;
    angle = (RANDOM_RANGE(60.0, 70.0)) * M_PI/180.0;
    direction = RANDOM_RANGE(0.0, 360.0) * M_PI/180.0;
    pointDirection[i][0] = cos(direction);
    pointDirection[i][1] = sin(direction);
    velocity = MEAN_VELOCITY + RANDOM_RANGE(-0.8, 1.0);
    pointVelocity[i][0] = velocity * cos(angle);
    pointVelocity[i][1] = velocity * sin(angle);
    colorList[i] = rand() % NUM_COLORS;
  }
  theTime = 0.0;
}

static void
updatePointList(void)
{
  float distance;
  int i;

  static double t0 = -1.;
  double dt, t = glutGet(GLUT_ELAPSED_TIME) / 1000.0;
  if (t0 < 0.0)
    t0 = t;
  dt = t - t0;
  t0 = t;

  motion = 0;
  for (i=0; i<numPoints; i++) {
    distance = pointVelocity[i][0] * theTime;

    /* X and Z */
    pointList[i][0] = pointDirection[i][0] * distance;
    pointList[i][2] = pointDirection[i][1] * distance;

    /* Z */
    pointList[i][1] =
      (pointVelocity[i][1] - 0.5 * GRAVITY * pointTime[i])*pointTime[i];

    /* If we hit the ground, bounce the point upward again. */
    if (pointList[i][1] <= 0.0) {
      if (distance > EDGE) {
        /* Particle has hit ground past the distance duration of
          the particles.  Mark particle as dead. */
       colorList[i] = NUM_COLORS;  /* Not moving. */
       continue;
      }

      pointVelocity[i][1] *= 0.8;  /* 80% of previous up velocity. */
      pointTime[i] = 0.0;  /* Reset the particles sense of up time. */
    }
    motion = 1;
    pointTime[i] += dt;
  }
  theTime += dt;
  if (!motion && !spin) {
    if (repeat) {
      makePointList();
    } else {
      glutIdleFunc(NULL);
    }
  }
}

static void
idle(void)
{
  updatePointList();
  if (spin) {
    angle += 0.3;
    newModel = 1;
  }
  glutPostRedisplay();
}

static void
visible(int vis)
{
  if (vis == GLUT_VISIBLE) {
    if (animate && (motion || spin)) {
      glutIdleFunc(idle);
    }
  } else {
    glutIdleFunc(NULL);
  }
}

static void
recalcModelView(void)
{
  glPopMatrix();
  glPushMatrix();
  glRotatef(angle, 0.0, 1.0, 0.0);
  newModel = 0;
}

static void
redraw(void)
{
  int i;

  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  if (newModel)
    recalcModelView();

  glDepthMask(GL_FALSE);

  /* Draw the floor. */
/*  glEnable(GL_TEXTURE_2D);*/
  glColor3f(0.5, 1.0, 0.5);
  glBegin(GL_QUADS);
    glTexCoord2f(0.0, 0.0);
    glVertex3f(-EDGE, -0.05, -EDGE);
    glTexCoord2f(20.0, 0.0);
    glVertex3f(EDGE, -0.05, -EDGE);
    glTexCoord2f(20.0, 20.0);
    glVertex3f(EDGE, -0.05, EDGE);
    glTexCoord2f(0.0, 20.0);
    glVertex3f(-EDGE, -0.05, EDGE);
  glEnd();

  /* Allow particles to blend with each other. */
  glDepthMask(GL_TRUE);

  if (blend)
     glEnable(GL_BLEND);

  glDisable(GL_TEXTURE_2D);
  glBegin(GL_POINTS);
    for (i=0; i<numPoints; i++) {
      /* Draw alive particles. */
      if (colorList[i] != DEAD) {
        glColor4fv(colorSet[colorList[i]]);
        glVertex3fv(pointList[i]);
      }
    }
  glEnd();

  glDisable(GL_BLEND);

  glutSwapBuffers();
}

/* ARGSUSED2 */
static void
mouse(int button, int state, int x, int y)
{
  /* Scene can be spun around Y axis using left
     mouse button movement. */
  if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN) {
    moving = 1;
    begin = x;
  }
  if (button == GLUT_LEFT_BUTTON && state == GLUT_UP) {
    moving = 0;
  }
}

/* ARGSUSED1 */
static void
mouseMotion(int x, int y)
{
  if (moving) {
    angle = angle + (x - begin);
    begin = x;
    newModel = 1;
    glutPostRedisplay();
  }
}

static void
menu(int option)
{
  switch (option) {
  case 0:
    makePointList();
    break;
#ifdef GL_ARB_point_parameters
  case 1:
    glPointParameterfvARB(GL_POINT_DISTANCE_ATTENUATION_ARB, constant);
    break;
  case 2:
    glPointParameterfvARB(GL_POINT_DISTANCE_ATTENUATION_ARB, linear);
    break;
  case 3:
    glPointParameterfvARB(GL_POINT_DISTANCE_ATTENUATION_ARB, theQuad);
    break;
#endif
  case 4:
    blend = 1;
    break;
  case 5:
    blend = 0;
    break;
#ifdef GL_ARB_point_parameters
  case 6:
    glPointParameterfARB(GL_POINT_FADE_THRESHOLD_SIZE_ARB, 1.0);
    break;
  case 7:
    glPointParameterfARB(GL_POINT_FADE_THRESHOLD_SIZE_ARB, 10.0);
    break;
#endif
  case 8:
    glEnable(GL_POINT_SMOOTH);
    break;
  case 9:
    glDisable(GL_POINT_SMOOTH);
    break;
  case 10:
    glPointSize(2.0);
    break;
  case 11:
    glPointSize(4.0);
    break;
  case 12:
    glPointSize(8.0);
    break;
  case 13:
    spin = 1 - spin;
    if (animate && (spin || motion)) {
      glutIdleFunc(idle);
    } else {
      glutIdleFunc(NULL);
    }
    break;
  case 14:
    numPoints = 200;
    break;
  case 15:
    numPoints = 500;
    break;
  case 16:
    numPoints = 1000;
    break;
  case 17:
    numPoints = 2000;
    break;
  case 666:
    exit(0);
  }
  glutPostRedisplay();
}

/* ARGSUSED1 */
static void
key(unsigned char c, int x, int y)
{
  switch (c) {
  case 13:
    animate = 1 - animate;  /* toggle. */
    if (animate && (motion || spin)) {
      glutIdleFunc(idle);
    } else {
      glutIdleFunc(NULL);
    }
    break;
  case ' ':
    animate = 1;
    makePointList();
    glutIdleFunc(idle);
    break;
  case 27:
    exit(0);
  }
}

/* Nice floor texture tiling pattern. */
static char *circles[] = {
  "....xxxx........",
  "..xxxxxxxx......",
  ".xxxxxxxxxx.....",
  ".xxx....xxx.....",
  "xxx......xxx....",
  "xxx......xxx....",
  "xxx......xxx....",
  "xxx......xxx....",
  ".xxx....xxx.....",
  ".xxxxxxxxxx.....",
  "..xxxxxxxx......",
  "....xxxx........",
  "................",
  "................",
  "................",
  "................",
};

static void
makeFloorTexture(void)
{
  GLubyte floorTexture[16][16][3];
  GLubyte *loc;
  int s, t;

  /* Setup RGB image for the texture. */
  loc = (GLubyte*) floorTexture;
  for (t = 0; t < 16; t++) {
    for (s = 0; s < 16; s++) {
      if (circles[t][s] == 'x') {
        /* Nice blue. */
        loc[0] = 0x1f;
        loc[1] = 0x1f;
        loc[2] = 0x8f;
      } else {
        /* Light gray. */
        loc[0] = 0xca;
        loc[1] = 0xca;
        loc[2] = 0xca;
      }
      loc += 3;
    }
  }

  glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

  if (useMipmaps) {
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
      GL_LINEAR_MIPMAP_LINEAR);
    gluBuild2DMipmaps(GL_TEXTURE_2D, 3, 16, 16,
      GL_RGB, GL_UNSIGNED_BYTE, floorTexture);
  } else {
    if (linearFiltering) {
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    } else {
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    }
    glTexImage2D(GL_TEXTURE_2D, 0, 3, 16, 16, 0,
      GL_RGB, GL_UNSIGNED_BYTE, floorTexture);
  }
}

int
main(int argc, char **argv)
{
  int i;
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH | GLUT_MULTISAMPLE);
  glutInitWindowPosition(0, 0);
  glutInitWindowSize(300, 300);

  for (i=1; i<argc; i++) {
    if(!strcmp("-noms", argv[i])) {
      glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
      printf("forcing no multisampling\n");
    } else if(!strcmp("-nomipmaps", argv[i])) {
      useMipmaps = 0;
    } else if(!strcmp("-nearest", argv[i])) {
      linearFiltering = 0;
    }
  }

  glutCreateWindow("point burst");
  glutDisplayFunc(redraw);
  glutMouseFunc(mouse);
  glutMotionFunc(mouseMotion);
  glutVisibilityFunc(visible);
  glutKeyboardFunc(key);
  glutCreateMenu(menu);
  glutAddMenuEntry("Reset time", 0);
  glutAddMenuEntry("Constant", 1);
  glutAddMenuEntry("Linear", 2);
  glutAddMenuEntry("Quadratic", 3);
  glutAddMenuEntry("Blend on", 4);
  glutAddMenuEntry("Blend off", 5);
  glutAddMenuEntry("Threshold 1", 6);
  glutAddMenuEntry("Threshold 10", 7);
  glutAddMenuEntry("Point smooth on", 8);
  glutAddMenuEntry("Point smooth off", 9);
  glutAddMenuEntry("Point size 2", 10);
  glutAddMenuEntry("Point size 4", 11);
  glutAddMenuEntry("Point size 8", 12);
  glutAddMenuEntry("Toggle spin", 13);
  glutAddMenuEntry("200 points ", 14);
  glutAddMenuEntry("500 points ", 15);
  glutAddMenuEntry("1000 points ", 16);
  glutAddMenuEntry("2000 points ", 17);
  glutAddMenuEntry("Quit", 666);
  glutAttachMenu(GLUT_RIGHT_BUTTON);

  if (!glutExtensionSupported("GL_ARB_point_parameters")) {
    fprintf(stderr, "Sorry, GL_ARB_point_parameters is not supported.\n");
    return -1;
  }

  glShadeModel(GL_FLAT);
  glEnable(GL_DEPTH_TEST);
  glEnable(GL_POINT_SMOOTH);
  glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
  glPointSize(8.0);
#if GL_ARB_point_parameters
  glPointParameterfvARB(GL_POINT_DISTANCE_ATTENUATION_ARB, theQuad);
#endif
  glMatrixMode(GL_PROJECTION);
  gluPerspective( /* field of view in degree */ 40.0,
  /* aspect ratio */ 1.0,
    /* Z near */ 0.5, /* Z far */ 40.0);
  glMatrixMode(GL_MODELVIEW);
  gluLookAt(0.0, 1.0, 8.0, /* eye location */
    0.0, 1.0, 0.0,      /* center is at (0,0,0) */
    0.0, 1.0, 0.);      /* up is in postivie Y direction */
  glPushMatrix();       /* dummy push so we can pop on model
                           recalc */

  makePointList();
  makeFloorTexture();

  glutMainLoop();
  return 0;             /* ANSI C requires main to return int. */
}
