lightposition.c

/*
  lightposition.c
  Nate Robins, 1997

  Tool for teaching about OpenGL light positioning.
        
*/


#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <GL/glut.h>
#include "glm.h"



typedef struct _cell {
  int id;
  int x, y;
  float min, max;
  float value;
  float step;
  char* info;
  char* format;
} cell;


cell lookat[9] = {
  {  1, 180, 120, -5.0, 5.0, 0.0, 0.1,
     "Specifies the X position of the eye point.", "%.2f" },
  {  2, 240, 120, -5.0, 5.0, 0.0, 0.1,
     "Specifies the Y position of the eye point.", "%.2f" },
  {  3, 300, 120, -5.0, 5.0, 2.0, 0.1,
     "Specifies the Z position of the eye point.", "%.2f" },
  {  4, 180, 160, -5.0, 5.0, 0.0, 0.1,
     "Specifies the X position of the reference point.", "%.2f" },
  {  5, 240, 160, -5.0, 5.0, 0.0, 0.1,
     "Specifies the Y position of the reference point.", "%.2f" },
  {  6, 300, 160, -5.0, 5.0, 0.0, 0.1,
     "Specifies the Z position of the reference point.", "%.2f" },
  {  7, 180, 200, -2.0, 2.0, 0.0, 0.1,
     "Specifies the X direction of the up vector.", "%.2f" },
  {  8, 240, 200, -2.0, 2.0, 1.0, 0.1,
     "Specifies the Y direction of the up vector.", "%.2f" },
  {  9, 300, 200, -2.0, 2.0, 0.0, 0.1,
     "Specifies the Z direction of the up vector.", "%.2f" },
};

cell light[4] = {
  { 10, 180, 40, -5.0, 5.0, 1.5, 0.1,
    "Specifies X coordinate of light vector.", "%.2f" },
  { 11, 240, 40, -5.0, 5.0, 1.0, 0.1,
    "Specifies Y coordinate of light vector.", "%.2f" },
  { 12, 300, 40, -5.0, 5.0, 1.0, 0.1,
    "Specifies Z coordinate of light vector.", "%.2f" },
  { 13, 360, 40, 0.0, 1.0, 0.0, 1.0,
    "Specifies directional (0) or positional (1) light.", "%.2f" }
};

GLboolean swapped = GL_FALSE;
GLboolean world_draw = GL_TRUE;
GLMmodel* pmodel = NULL;
GLint selection = 0;

void redisplay_all(void);
GLdouble projection[16], modelview[16], inverse[16];
GLuint window, world, screen, command;
GLuint sub_width = 256, sub_height = 256;


GLvoid *font_style = GLUT_BITMAP_TIMES_ROMAN_10;

void
setfont(char* name, int size)
{
  font_style = GLUT_BITMAP_HELVETICA_10;
  if (strcmp(name, "helvetica") == 0) {
    if (size == 12) 
      font_style = GLUT_BITMAP_HELVETICA_12;
    else if (size == 18)
      font_style = GLUT_BITMAP_HELVETICA_18;
  } else if (strcmp(name, "times roman") == 0) {
    font_style = GLUT_BITMAP_TIMES_ROMAN_10;
    if (size == 24)
      font_style = GLUT_BITMAP_TIMES_ROMAN_24;
  } else if (strcmp(name, "8x13") == 0) {
    font_style = GLUT_BITMAP_8_BY_13;
  } else if (strcmp(name, "9x15") == 0) {
    font_style = GLUT_BITMAP_9_BY_15;
  }
}

void 
drawstr(GLuint x, GLuint y, char* format, ...)
{
  va_list args;
  char buffer[255], *s;
    
  va_start(args, format);
  vsprintf(buffer, format, args);
  va_end(args);
    
  glRasterPos2i(x, y);
  for (s = buffer; *s; s++)
    glutBitmapCharacter(font_style, *s);
}

void
cell_draw(cell* cell)
{
  glColor3ub(0, 255, 128);
  if (selection == cell->id) {
    glColor3ub(255, 255, 0);
    drawstr(10, 240, cell->info);
    glColor3ub(255, 0, 0);
  }

  drawstr(cell->x, cell->y, cell->format, cell->value);
}

int
cell_hit(cell* cell, int x, int y)
{
  if (x > cell->x && x < cell->x + 60 &&
      y > cell->y-30 && y < cell->y+10)
    return cell->id;
  return 0;
}

void
cell_update(cell* cell, int update)
{
  if (selection != cell->id)
    return;

  cell->value += update * cell->step;

  if (cell->value < cell->min)
    cell->value = cell->min;
  else if (cell->value > cell->max) 
    cell->value = cell->max;

}

void
cell_vector(float* dst, cell* cell, int num)
{
  while (--num >= 0)
    dst[num] = cell[num].value;
}

void
drawmodel(void)
{
  if (!pmodel) {
    pmodel = glmReadOBJ("data/soccerball.obj");
    if (!pmodel) exit(0);
    glmUnitize(pmodel);
    glmFacetNormals(pmodel);
    glmVertexNormals(pmodel, 90.0);
  }

  glmDraw(pmodel, GLM_SMOOTH | GLM_MATERIAL);
}

void
drawaxes(void)
{
  glColor3ub(255, 0, 0);
  glBegin(GL_LINE_STRIP);
  glVertex3f(0.0, 0.0, 0.0);
  glVertex3f(1.0, 0.0, 0.0);
  glVertex3f(0.75, 0.25, 0.0);
  glVertex3f(0.75, -0.25, 0.0);
  glVertex3f(1.0, 0.0, 0.0);
  glVertex3f(0.75, 0.0, 0.25);
  glVertex3f(0.75, 0.0, -0.25);
  glVertex3f(1.0, 0.0, 0.0);
  glEnd();
  glBegin(GL_LINE_STRIP);
  glVertex3f(0.0, 0.0, 0.0);
  glVertex3f(0.0, 1.0, 0.0);
  glVertex3f(0.0, 0.75, 0.25);
  glVertex3f(0.0, 0.75, -0.25);
  glVertex3f(0.0, 1.0, 0.0);
  glVertex3f(0.25, 0.75, 0.0);
  glVertex3f(-0.25, 0.75, 0.0);
  glVertex3f(0.0, 1.0, 0.0);
  glEnd();
  glBegin(GL_LINE_STRIP);
  glVertex3f(0.0, 0.0, 0.0);
  glVertex3f(0.0, 0.0, 1.0);
  glVertex3f(0.25, 0.0, 0.75);
  glVertex3f(-0.25, 0.0, 0.75);
  glVertex3f(0.0, 0.0, 1.0);
  glVertex3f(0.0, 0.25, 0.75);
  glVertex3f(0.0, -0.25, 0.75);
  glVertex3f(0.0, 0.0, 1.0);
  glEnd();

  glColor3ub(255, 255, 0);
  glRasterPos3f(1.1, 0.0, 0.0);
  glutBitmapCharacter(GLUT_BITMAP_HELVETICA_12, 'x');
  glRasterPos3f(0.0, 1.1, 0.0);
  glutBitmapCharacter(GLUT_BITMAP_HELVETICA_12, 'y');
  glRasterPos3f(0.0, 0.0, 1.1);
  glutBitmapCharacter(GLUT_BITMAP_HELVETICA_12, 'z');
}

void
identity(GLdouble m[16])
{
  m[0+4*0] = 1; m[0+4*1] = 0; m[0+4*2] = 0; m[0+4*3] = 0;
  m[1+4*0] = 0; m[1+4*1] = 1; m[1+4*2] = 0; m[1+4*3] = 0;
  m[2+4*0] = 0; m[2+4*1] = 0; m[2+4*2] = 1; m[2+4*3] = 0;
  m[3+4*0] = 0; m[3+4*1] = 0; m[3+4*2] = 0; m[3+4*3] = 1;
}

GLboolean
invert(GLdouble src[16], GLdouble inverse[16])
{
  double t;
  int i, j, k, swap;
  GLdouble tmp[4][4];

  identity(inverse);

  for (i = 0; i < 4; i++) {
    for (j = 0; j < 4; j++) {
      tmp[i][j] = src[i*4+j];
    }
  }

  for (i = 0; i < 4; i++) {
    /* look for largest element in column. */
    swap = i;
    for (j = i + 1; j < 4; j++) {
      if (fabs(tmp[j][i]) > fabs(tmp[i][i])) {
        swap = j;
      }
    }

    if (swap != i) {
      /* swap rows. */
      for (k = 0; k < 4; k++) {
        t = tmp[i][k];
        tmp[i][k] = tmp[swap][k];
        tmp[swap][k] = t;

        t = inverse[i*4+k];
        inverse[i*4+k] = inverse[swap*4+k];
        inverse[swap*4+k] = t;
      }
    }

    if (tmp[i][i] == 0) {
      /* no non-zero pivot.  the matrix is singular, which
         shouldn't happen.  This means the user gave us a bad
         matrix. */
      return GL_FALSE;
    }

    t = tmp[i][i];
    for (k = 0; k < 4; k++) {
      tmp[i][k] /= t;
      inverse[i*4+k] /= t;
    }
    for (j = 0; j < 4; j++) {
      if (j != i) {
        t = tmp[j][i];
        for (k = 0; k < 4; k++) {
          tmp[j][k] -= tmp[i][k]*t;
          inverse[j*4+k] -= inverse[i*4+k]*t;
        }
      }
    }
  }
  return GL_TRUE;
}

float
normalize(float* v)
{
  float length;

  length = sqrt(v[0]*v[0] + v[1]*v[1] + v[2]*v[2]);
  v[0] /= length;
  v[1] /= length;
  v[2] /= length;

  return length;
}

void
main_reshape(int width,  int height) 
{
  glViewport(0, 0, width, height);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluOrtho2D(0, width, height, 0);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();

#define GAP  25                         /* gap between subwindows */
  sub_width = (width-GAP*3)/2.0;
  sub_height = (height-GAP*3)/2.0;

  glutSetWindow(world);
  glutPositionWindow(GAP, GAP);
  glutReshapeWindow(sub_width, sub_height);
  glutSetWindow(screen);
  glutPositionWindow(GAP+sub_width+GAP, GAP);
  glutReshapeWindow(sub_width, sub_height);
  glutSetWindow(command);
  glutPositionWindow(GAP, GAP+sub_height+GAP);
  glutReshapeWindow(sub_width+GAP+sub_width, sub_height);
}

void
main_display(void)
{
  glClearColor(0.8, 0.8, 0.8, 0.0);
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glColor3ub(0, 0, 0);
  setfont("helvetica", 12);
  drawstr(GAP, GAP-5, "World-space view");
  drawstr(GAP+sub_width+GAP, GAP-5, "Screen-space view");
  drawstr(GAP, GAP+sub_height+GAP-5, "Command manipulation window");
  glutSwapBuffers();
}

void
main_keyboard(char key, int x, int y)
{
  switch (key) {
  case 's':
    swapped = !swapped;
    break;
  case 'r':
    light[0].value = 1.5;
    light[1].value = 1.0;
    light[2].value = 1.0;
    light[3].value = 0.0;
    lookat[0].value = 0.0;
    lookat[1].value = 0.0;
    lookat[2].value = 2.0;
    lookat[3].value = 0.0;
    lookat[4].value = 0.0;
    lookat[5].value = 0.0;
    lookat[6].value = 0.0;
    lookat[7].value = 1.0;
    lookat[8].value = 0.0;
    break;
  case 27:
    exit(0);
  }

  redisplay_all();
}

void
world_reshape(int width, int height)
{
  glViewport(0, 0, width, height);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluPerspective(60.0, (GLfloat)width/height, 0.01, 256.0);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  glTranslatef(0.0, 0.0, -5.0);
  glRotatef(-45.0, 0.0, 1.0, 0.0);
  glClearColor(0.0, 0.0, 0.0, 0.0);
  glEnable(GL_DEPTH_TEST);
  glEnable(GL_LIGHT0);
}

void
world_display(void)
{
  GLfloat pos[4];
  double length;
  float l[3];

  cell_vector(pos, light, 4);
  l[0] = lookat[3].value - lookat[0].value; 
  l[1] = lookat[4].value - lookat[1].value; 
  l[2] = lookat[5].value - lookat[2].value;

  invert(modelview, inverse);

  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

  if (swapped) {
    glPushMatrix();
    glTranslatef(l[0], l[1], l[2]);
    glMultMatrixd(inverse);
    glColor3ub(255, 255, 255);
    glBegin(GL_LINE_STRIP);
    glVertex3f(0.0, 0.0, 0.0);
    if (pos[3] == 0)            /* 10.0 = 'infinite' light */
      glVertex3f(pos[0]*10.0,pos[1]*10.0,pos[2]*10.0);
    else 
      glVertex3f(pos[0], pos[1], pos[2]);
    glEnd();
    glLightfv(GL_LIGHT0, GL_POSITION, pos);
    glPopMatrix();
  } else {
    glColor3ub(255, 255, 255);
    glBegin(GL_LINE_STRIP);
    glVertex3f(0.0, 0.0, 0.0);
    if (pos[3] == 0)            /* 10.0 = 'infinite' light */
      glVertex3f(pos[0]*10.0,pos[1]*10.0,pos[2]*10.0);
    else 
      glVertex3f(pos[0], pos[1], pos[2]);
    glEnd();
    glLightfv(GL_LIGHT0, GL_POSITION, pos);
  }

  length = normalize(l);

  if (world_draw) {
    glEnable(GL_LIGHTING);
    drawmodel();
    glDisable(GL_LIGHTING);
  }

  glPushMatrix();
  glMultMatrixd(inverse);

  /* draw the axes and eye vector */
  glPushMatrix();
  glColor3ub(0, 0, 255);
  glBegin(GL_LINE_STRIP);
  glVertex3f(0.0, 0.0, 0.0);
  glVertex3f(0.0, 0.0, -1.0*length);
  glVertex3f(0.1, 0.0, -0.9*length);
  glVertex3f(-0.1, 0.0, -0.9*length);
  glVertex3f(0.0, 0.0, -1.0*length);
  glVertex3f(0.0, 0.1, -0.9*length);
  glVertex3f(0.0, -0.1, -0.9*length);
  glVertex3f(0.0, 0.0, -1.0*length);
  glEnd();
  glColor3ub(255, 255, 0);
  glRasterPos3f(0.0, 0.0, -1.1*length);
  glutBitmapCharacter(GLUT_BITMAP_HELVETICA_12, 'e');
  glColor3ub(255, 0, 0);
  glScalef(0.4, 0.4, 0.4);
  drawaxes();
  glPopMatrix();

  invert(projection, inverse);
  glMultMatrixd(inverse);

  /* draw the viewing frustum */
  glColor3f(0.2, 0.2, 0.2);
  glBegin(GL_QUADS);
  glVertex3i(1, 1, 1);
  glVertex3i(-1, 1, 1);
  glVertex3i(-1, -1, 1);
  glVertex3i(1, -1, 1);
  glEnd();

  glColor3ub(128, 196, 128);
  glBegin(GL_LINES);
  glVertex3i(1, 1, -1);
  glVertex3i(1, 1, 1);
  glVertex3i(-1, 1, -1);
  glVertex3i(-1, 1, 1);
  glVertex3i(-1, -1, -1);
  glVertex3i(-1, -1, 1);
  glVertex3i(1, -1, -1);
  glVertex3i(1, -1, 1);
  glEnd();

  glEnable(GL_BLEND);
  glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
  glColor4f(0.2, 0.2, 0.4, 0.5);
  glBegin(GL_QUADS);
  glVertex3i(1, 1, -1);
  glVertex3i(-1, 1, -1);
  glVertex3i(-1, -1, -1);
  glVertex3i(1, -1, -1);
  glEnd();
  glDisable(GL_BLEND);

  glPopMatrix();
  glutSwapBuffers();
}

void
world_menu(int value)
{
  switch (value) {
  case 'm':
    world_draw = !world_draw;
    break;
  }
  redisplay_all();
}

void
screen_reshape(int width, int height)
{
  GLfloat pos[4];
  cell_vector(pos, light, 4);

  glViewport(0, 0, width, height);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluPerspective(60.0, (float)width/height, 0.5, 8.0);
  glGetDoublev(GL_PROJECTION_MATRIX, projection);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  if (swapped) {
    glLightfv(GL_LIGHT0, GL_POSITION, pos);
    gluLookAt(lookat[0].value, lookat[1].value, lookat[2].value,
              lookat[3].value, lookat[4].value, lookat[5].value,
              lookat[6].value, lookat[7].value, lookat[8].value);
  } else {
    gluLookAt(lookat[0].value, lookat[1].value, lookat[2].value,
              lookat[3].value, lookat[4].value, lookat[5].value,
              lookat[6].value, lookat[7].value, lookat[8].value);
    glLightfv(GL_LIGHT0, GL_POSITION, pos);
  }
  glGetDoublev(GL_MODELVIEW_MATRIX, modelview);
  glClearColor(0.2, 0.2, 0.2, 0.0);
  glEnable(GL_DEPTH_TEST);
  glEnable(GL_LIGHTING);
  glEnable(GL_LIGHT0);
}

void
screen_display(void)
{
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  drawmodel();
  glutSwapBuffers();
}

void
screen_menu(int value)
{
  char* name = 0;

  switch (value) {
  case 'a':
    name = "data/al.obj";
    break;
  case 's':
    name = "data/soccerball.obj";
    break;
  case 'd':
    name = "data/dolphins.obj";
    break;
  case 'f':
    name = "data/flowers.obj";
    break;
  case 'j':
    name = "data/f-16.obj";
    break;
  case 'p':
    name = "data/porsche.obj";
    break;
  case 'r':
    name = "data/rose+vase.obj";
    break;
  }

  if (name) {
    pmodel = glmReadOBJ(name);
    if (!pmodel) exit(0);
    glmUnitize(pmodel);
    glmFacetNormals(pmodel);
    glmVertexNormals(pmodel, 90.0);
  }

  redisplay_all();
}

void
command_reshape(int width, int height)
{
  glViewport(0, 0, width, height);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluOrtho2D(0, width, height, 0);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  glClearColor(0.0, 0.0, 0.0, 0.0);
}

void
command_display(void)
{
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

  glColor3ub(255, 255, 255);

  setfont("helvetica", 18);
  if (swapped) {
    lookat[0].y = 120;
    lookat[1].y = 120;
    lookat[2].y = 120;
    lookat[3].y = 120+40;
    lookat[4].y = 120+40;
    lookat[5].y = 120+40;
    lookat[6].y = 120+80;
    lookat[7].y = 120+80;
    lookat[8].y = 120+80;
  } else {
    lookat[0].y = 80;
    lookat[1].y = 80;
    lookat[2].y = 80;
    lookat[3].y = 80+40;
    lookat[4].y = 80+40;
    lookat[5].y = 80+40;
    lookat[6].y = 80+80;
    lookat[7].y = 80+80;
    lookat[8].y = 80+80;
  }

  drawstr(30, light[0].y, "GLfloat pos[4] = {");
  drawstr(230, light[0].y, ",");
  drawstr(290, light[0].y, ","); 
  drawstr(350, light[0].y, ",");
  drawstr(410, light[0].y, "};");
  if (swapped)
    drawstr(30, 80, "glLightfv(GL_LIGHT0, GL_POSITION, pos);");
  else
    drawstr(30, 200, "glLightfv(GL_LIGHT0, GL_POSITION, pos);");
  drawstr(78, lookat[0].y, "gluLookAt(");
  drawstr(230, lookat[0].y, ","); 
  drawstr(290, lookat[0].y, ",");
  drawstr(350, lookat[0].y, ",");
  drawstr(380, lookat[0].y, "<- eye");
  drawstr(230, lookat[3].y, ","); 
  drawstr(290, lookat[3].y, ",");
  drawstr(350, lookat[3].y, ",");
  drawstr(380, lookat[3].y, "<- center");
  drawstr(230, lookat[6].y, ","); 
  drawstr(290, lookat[6].y, ",");
  drawstr(350, lookat[6].y, ");");
  drawstr(380, lookat[6].y, "<- up");

  cell_draw(&light[0]);
  cell_draw(&light[1]);
  cell_draw(&light[2]);
  cell_draw(&light[3]);

  cell_draw(&lookat[0]);
  cell_draw(&lookat[1]);
  cell_draw(&lookat[2]);
  cell_draw(&lookat[3]);
  cell_draw(&lookat[4]);
  cell_draw(&lookat[5]);
  cell_draw(&lookat[6]);
  cell_draw(&lookat[7]);
  cell_draw(&lookat[8]);

  if (!selection) {
    glColor3ub(255, 255, 0);
    drawstr(10, 240,
            "Click on the arguments and move the mouse to modify values.");
  }   
    
  glutSwapBuffers();
}

int old_y;

void
command_mouse(int button, int state, int x, int y)
{
  selection = 0;

  if (state == GLUT_DOWN) {
    /* mouse should only hit _one_ of the cells, so adding up all
       the hits just propagates a single hit. */
    selection += cell_hit(&light[0], x, y);
    selection += cell_hit(&light[1], x, y);
    selection += cell_hit(&light[2], x, y);
    selection += cell_hit(&light[3], x, y);
    selection += cell_hit(&lookat[0], x, y);
    selection += cell_hit(&lookat[1], x, y);
    selection += cell_hit(&lookat[2], x, y);
    selection += cell_hit(&lookat[3], x, y);
    selection += cell_hit(&lookat[4], x, y);
    selection += cell_hit(&lookat[5], x, y);
    selection += cell_hit(&lookat[6], x, y);
    selection += cell_hit(&lookat[7], x, y);
    selection += cell_hit(&lookat[8], x, y);
  }

  old_y = y;

  redisplay_all();
}

void
command_motion(int x, int y)
{
  cell_update(&light[0], old_y-y);
  cell_update(&light[1], old_y-y);
  cell_update(&light[2], old_y-y);
  cell_update(&light[3], old_y-y);
  cell_update(&lookat[0], old_y-y);
  cell_update(&lookat[1], old_y-y);
  cell_update(&lookat[2], old_y-y);
  cell_update(&lookat[3], old_y-y);
  cell_update(&lookat[4], old_y-y);
  cell_update(&lookat[5], old_y-y);
  cell_update(&lookat[6], old_y-y);
  cell_update(&lookat[7], old_y-y);
  cell_update(&lookat[8], old_y-y);
    
  old_y = y;
    
  redisplay_all();
}

void
command_menu(int value)
{
  main_keyboard((unsigned char)value, 0, 0);
}

void
redisplay_all(void)
{
  glutSetWindow(command);
  glutPostRedisplay();
  glutSetWindow(world);
  world_reshape(sub_width, sub_height);
  glutPostRedisplay();
  glutSetWindow(screen);
  screen_reshape(sub_width, sub_height);
  glutPostRedisplay();
}

int
main(int argc, char** argv)
{
  glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE);
  glutInitWindowSize(512+GAP*3, 512+GAP*3);
  glutInitWindowPosition(50, 50);
  glutInit(&argc, argv);

  window = glutCreateWindow("Light Positioning");
  glutReshapeFunc(main_reshape);
  glutDisplayFunc(main_display);
  glutKeyboardFunc(main_keyboard);

  world = glutCreateSubWindow(window, GAP, GAP, 256, 256);
  glutReshapeFunc(world_reshape);
  glutDisplayFunc(world_display);
  glutKeyboardFunc(main_keyboard);
  glutCreateMenu(world_menu);
  glutAddMenuEntry("Toggle model", 'm');
  glutAttachMenu(GLUT_RIGHT_BUTTON);

  screen = glutCreateSubWindow(window, GAP+256+GAP, GAP, 256, 256);
  glutReshapeFunc(screen_reshape);
  glutDisplayFunc(screen_display);
  glutKeyboardFunc(main_keyboard);
  glutCreateMenu(screen_menu);
  glutAddMenuEntry("Models", 0);
  glutAddMenuEntry("", 0);
  glutAddMenuEntry("Soccerball", 's');
  glutAddMenuEntry("Al Capone", 'a');
  glutAddMenuEntry("F-16 Jet", 'j');
  glutAddMenuEntry("Dolphins", 'd');
  glutAddMenuEntry("Flowers", 'f');
  glutAddMenuEntry("Porsche", 'p');
  glutAddMenuEntry("Rose", 'r');
  glutAttachMenu(GLUT_RIGHT_BUTTON);

  command = glutCreateSubWindow(window, GAP+256+GAP, GAP+256+GAP, 256, 256);
  glutReshapeFunc(command_reshape);
  glutDisplayFunc(command_display);
  glutMotionFunc(command_motion);
  glutMouseFunc(command_mouse);
  glutKeyboardFunc(main_keyboard);
  glutCreateMenu(command_menu);
  glutAddMenuEntry("Light Positioning", 0);
  glutAddMenuEntry("", 0);
  glutAddMenuEntry("[s]  Swap lookat/position calls", 's');
  glutAddMenuEntry("[r]  Reset parameters", 'r');
  glutAddMenuEntry("", 0);
  glutAddMenuEntry("Quit", 27);
  glutAttachMenu(GLUT_RIGHT_BUTTON);

  redisplay_all();

  glutMainLoop();

  return 0;
}