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/*
fog.c
Nate Robins, 1997
Tool for teaching about OpenGL fog.
*/
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <GL/glut.h>
#include "glm.h"
#pragma comment( linker, "/entry:\"mainCRTStartup\"" ) // set the entry point to be main()
typedef struct _cell {
int id;
int x, y;
float min, max;
float value;
float step;
char* info;
char* format;
} cell;
cell color[4] = {
{ 1, 180, 40, 0.0, 1.0, 0.7, 0.005,
"Specifies red component of fog color.", "%.2f" },
{ 2, 240, 40, 0.0, 1.0, 0.7, 0.005,
"Specifies green component of fog color.", "%.2f" },
{ 3, 300, 40, 0.0, 1.0, 0.7, 0.005,
"Specifies blue component of fog color.", "%.2f" },
{ 4, 360, 40, 0.0, 1.0, 1.0, 0.005,
"Specifies alpha component of fog color.", "%.2f" }
};
cell density = { 5, 260, 120, 0.0, 3.0, 1.0, 0.01,
"Specifies the near distance.", "%.2f" };
cell fstart = { 6, 240, 120, -3.0, 3.0, 0.5, 0.01,
"Specifies the far distance.", "%.2f" };
cell fend = { 7, 240, 160, -3.0, 3.0, 2.0, 0.01,
"Specifies the fog density.", "%.2f" };
GLenum mode = GL_LINEAR;
GLboolean clear = GL_TRUE;
GLMmodel* pmodel = NULL;
GLfloat eye[3] = { 0.5, 0.25, 1.5 };
GLfloat at[3] = { 0.0, -0.25, 0.0 };
GLfloat up[3] = { 0.0, 1.0, 0.0 };
void redisplay_all(void);
GLuint window, world, screen, command;
GLuint sub_width = 256, sub_height = 256;
GLint selection = 0;
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/f-16.obj");
if (!pmodel) exit(0);
glmUnitize(pmodel);
glmFacetNormals(pmodel);
glmVertexNormals(pmodel, 90.0);
}
glmDraw(pmodel, GLM_SMOOTH | GLM_MATERIAL);
}
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, "Fog equation");
drawstr(GAP+sub_width+GAP, GAP-5, "Screen-space view");
drawstr(GAP, GAP+sub_height+GAP-5, "Command manipulation window");
glutSwapBuffers();
}
void
main_keyboard(unsigned char key, int x, int y)
{
switch (key) {
case 'l':
mode = GL_LINEAR;
break;
case 'e':
mode = GL_EXP;
break;
case 'x':
mode = GL_EXP2;
break;
case 'c':
clear = !clear;
break;
case 'r':
color[0].value = 0.7;
color[1].value = 0.7;
color[2].value = 0.7;
color[3].value = 1.0;
density.value = 1.0;
fstart.value = 0.5;
fend.value = 2.0;
break;
case 27:
exit(0);
}
redisplay_all();
}
void
world_reshape(int width, int height)
{
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, width, height, 0, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glLineWidth(2.0);
}
void
world_display(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glColor3ub(255, 255, 255);
setfont("helvetica", 18);
if (mode == GL_LINEAR) {
drawstr(100, 80, "end - z");
drawstr(30, 95, "f = ");
drawstr(90, 110, "end - start");
glBegin(GL_LINE_STRIP);
glVertex2i(85, 90);
glVertex2i(185, 90);
glEnd();
} else {
drawstr(90, 80, "- (density * z)");
drawstr(30, 95, "f = e");
if (mode == GL_EXP2)
drawstr(208, 68, "2");
}
setfont("helvetica", 12);
drawstr(20, 180, "z is the distance in eye coordinates");
drawstr(20, 195, "from origin to fragment being fogged.");
glutSwapBuffers();
}
void
screen_reshape(int width, int height)
{
float fog_color[4];
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(60.0, (float)width/height, 0.5, 8.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(eye[0], eye[1], eye[2], at[0], at[1], at[2], up[0], up[1],up[2]);
if (clear)
glClearColor(color[0].value, color[1].value,
color[2].value, color[3].value);
else
glClearColor(0.2, 0.2, 0.2, 1.0);
glEnable(GL_DEPTH_TEST);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glEnable(GL_FOG);
glFogi(GL_FOG_MODE, mode);
glFogf(GL_FOG_START, fstart.value);
glFogf(GL_FOG_END, fend.value);
glFogf(GL_FOG_DENSITY, density.value);
cell_vector(fog_color, color, 4);
glFogfv(GL_FOG_COLOR, fog_color);
}
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);
drawstr(20, color[0].y, "GLfloat color[4] = {");
drawstr(230, color[0].y, ",");
drawstr(290, color[0].y, ",");
drawstr(350, color[0].y, ",");
drawstr(410, color[0].y, "};");
drawstr(20, 80, "glFogfv(GL_FOG_COLOR, color);");
if (mode == GL_LINEAR) {
drawstr(20, fstart.y, "glFogf(GL_FOG_START, ");
drawstr(290, fstart.y, ");");
drawstr(20, fend.y, "glFogf(GL_FOG_END, ");
drawstr(290, fend.y, ");");
} else {
drawstr(20, density.y, "glFogf(GL_FOG_DENSITY, ");
drawstr(310, density.y, ");");
}
drawstr(20, 200, "glFogi(GL_FOG_MODE, %s);",
mode == GL_LINEAR ? "GL_LINEAR" :
mode == GL_EXP ? "GL_EXP" : "GL_EXP2");
cell_draw(&color[0]);
cell_draw(&color[1]);
cell_draw(&color[2]);
cell_draw(&color[3]);
if (mode == GL_LINEAR) {
cell_draw(&fstart);
cell_draw(&fend);
} else {
cell_draw(&density);
}
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(&color[0], x, y);
selection += cell_hit(&color[1], x, y);
selection += cell_hit(&color[2], x, y);
selection += cell_hit(&color[3], x, y);
if (mode == GL_LINEAR) {
selection += cell_hit(&fstart, x, y);
selection += cell_hit(&fend, x, y);
} else {
selection += cell_hit(&density, x, y);
}
}
old_y = y;
redisplay_all();
}
void
command_motion(int x, int y)
{
cell_update(&color[0], old_y-y);
cell_update(&color[1], old_y-y);
cell_update(&color[2], old_y-y);
cell_update(&color[3], old_y-y);
cell_update(&fstart, old_y-y);
cell_update(&fend, old_y-y);
cell_update(&density, 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("Fog");
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);
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("Fog", 0);
glutAddMenuEntry("", 0);
glutAddMenuEntry("[l] GL_LINEAR", 'l');
glutAddMenuEntry("[e] GL_EXP", 'e');
glutAddMenuEntry("[x] GL_EXP2", 'x');
glutAddMenuEntry("[c] Clear color toggle", 'c');
glutAddMenuEntry("[r] Reset parameters", 'r');
glutAddMenuEntry("", 0);
glutAddMenuEntry("Quit", 27);
glutAttachMenu(GLUT_RIGHT_BUTTON);
redisplay_all();
glutMainLoop();
return 0;
}
]]>