--- /dev/null
+/*
+ * EXT_fog_coord.
+ *
+ * Based on glutskel.c by Brian Paul
+ * and NeHe's Volumetric fog tutorial!
+ *
+ * Daniel Borca
+ */
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <GL/glut.h>
+
+#include "readtex.c" /* the compulsory hack */
+
+#define TEXTURE_FILE "../images/bw.rgb"
+
+#define ARRAYS 0 /* use glDrawElements */
+
+#define VERBOSE 1 /* tell me what happens */
+
+#define DEPTH 15.0f
+#define EPS 1e-6f
+
+typedef void (GLAPIENTRYP GLFOGCOORDFEXTPROC) (GLfloat f);
+typedef void (GLAPIENTRYP GLFOGCOORDPOINTEREXTPROC) (GLenum, GLsizei, const GLvoid *);
+
+static GLFOGCOORDFEXTPROC glFogCoordf_ext;
+static GLFOGCOORDPOINTEREXTPROC glFogCoordPointer_ext;
+static GLboolean have_fog_coord;
+
+static GLfloat camz;
+static GLuint texture[1];
+
+static GLint fogMode;
+static GLboolean fogCoord;
+static GLfloat fogDensity = 0.75;
+static GLfloat fogStart = 0.0, fogEnd = 1.0;
+static GLfloat fogColor[4] = {0.6f, 0.3f, 0.0f, 1.0f};
+
+
+void APIENTRY glFogCoordf_nop (GLfloat f)
+{
+ (void)f;
+}
+
+
+static int BuildTexture (const char *filename, GLuint texid[])
+{
+ GLubyte *tex_data;
+ GLenum tex_format;
+ GLint tex_width, tex_height;
+
+ tex_data = LoadRGBImage(filename, &tex_width, &tex_height, &tex_format);
+ if (tex_data == NULL) {
+ return -1;
+ }
+
+ {
+ GLint tex_max;
+ glGetIntegerv(GL_MAX_TEXTURE_SIZE, &tex_max);
+ if ((tex_width > tex_max) || (tex_height > tex_max)) {
+ return -1;
+ }
+ }
+
+ glGenTextures(1, texid);
+
+ glBindTexture(GL_TEXTURE_2D, texid[0]);
+ glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+ glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+
+ glTexImage2D(GL_TEXTURE_2D, 0, tex_format, tex_width, tex_height, 0, tex_format, GL_UNSIGNED_BYTE, tex_data);
+
+ return 0;
+}
+
+
+static int SetFogMode (GLint fogMode)
+{
+ fogMode &= 3;
+ switch (fogMode) {
+ case 0:
+ glDisable(GL_FOG);
+#if VERBOSE
+ printf("fog(disable)\n");
+#endif
+ break;
+ case 1:
+ glEnable(GL_FOG);
+ glFogi(GL_FOG_MODE, GL_LINEAR);
+ glFogf(GL_FOG_START, fogStart);
+ glFogf(GL_FOG_END, fogEnd);
+#if VERBOSE
+ printf("fog(GL_LINEAR, %.2f, %.2f)\n", fogStart, fogEnd);
+#endif
+ break;
+ case 2:
+ glEnable(GL_FOG);
+ glFogi(GL_FOG_MODE, GL_EXP);
+ glFogf(GL_FOG_DENSITY, fogDensity);
+#if VERBOSE
+ printf("fog(GL_EXP, %.2f)\n", fogDensity);
+#endif
+ break;
+ case 3:
+ glEnable(GL_FOG);
+ glFogi(GL_FOG_MODE, GL_EXP2);
+ glFogf(GL_FOG_DENSITY, fogDensity);
+#if VERBOSE
+ printf("fog(GL_EXP2, %.2f)\n", fogDensity);
+#endif
+ break;
+ }
+ return fogMode;
+}
+
+
+static GLboolean SetFogCoord (GLboolean fogCoord)
+{
+ glFogCoordf_ext = glFogCoordf_nop;
+
+ if (!have_fog_coord) {
+#if VERBOSE
+ printf("fog(GL_FRAGMENT_DEPTH_EXT)%s\n", fogCoord ? " EXT_fog_coord not available!" : "");
+#endif
+ return GL_FALSE;
+ }
+
+ if (fogCoord) {
+ glFogCoordf_ext = (GLFOGCOORDFEXTPROC)glutGetProcAddress("glFogCoordfEXT");
+ glFogi(GL_FOG_COORDINATE_SOURCE_EXT, GL_FOG_COORDINATE_EXT);
+#if VERBOSE
+ printf("fog(GL_FOG_COORDINATE_EXT)\n");
+#endif
+ } else {
+ glFogi(GL_FOG_COORDINATE_SOURCE_EXT, GL_FRAGMENT_DEPTH_EXT);
+#if VERBOSE
+ printf("fog(GL_FRAGMENT_DEPTH_EXT)\n");
+#endif
+ }
+ return fogCoord;
+}
+
+
+#if ARRAYS
+/* could reuse vertices */
+static GLuint vertex_index[] = {
+ /* Back */
+ 0, 1, 2, 3,
+
+ /* Floor */
+ 4, 5, 6, 7,
+
+ /* Roof */
+ 8, 9, 10, 11,
+
+ /* Right */
+ 12, 13, 14, 15,
+
+ /* Left */
+ 16, 17, 18, 19
+};
+
+static GLfloat vertex_pointer[][3] = {
+ /* Back */
+ {-2.5f,-2.5f,-DEPTH}, { 2.5f,-2.5f,-DEPTH}, { 2.5f, 2.5f,-DEPTH}, {-2.5f, 2.5f,-DEPTH},
+
+ /* Floor */
+ {-2.5f,-2.5f,-DEPTH}, { 2.5f,-2.5f,-DEPTH}, { 2.5f,-2.5f, DEPTH}, {-2.5f,-2.5f, DEPTH},
+
+ /* Roof */
+ {-2.5f, 2.5f,-DEPTH}, { 2.5f, 2.5f,-DEPTH}, { 2.5f, 2.5f, DEPTH}, {-2.5f, 2.5f, DEPTH},
+
+ /* Right */
+ { 2.5f,-2.5f, DEPTH}, { 2.5f, 2.5f, DEPTH}, { 2.5f, 2.5f,-DEPTH}, { 2.5f,-2.5f,-DEPTH},
+
+ /* Left */
+ {-2.5f,-2.5f, DEPTH}, {-2.5f, 2.5f, DEPTH}, {-2.5f, 2.5f,-DEPTH}, {-2.5f,-2.5f,-DEPTH}
+};
+
+static GLfloat texcoord_pointer[][2] = {
+ /* Back */
+ {0.0f, 0.0f}, {1.0f, 0.0f}, {1.0f, 1.0f}, {0.0f, 1.0f},
+
+ /* Floor */
+ {0.0f, 0.0f}, {1.0f, 0.0f}, {1.0f, 1.0f}, {0.0f, 1.0f},
+
+ /* Roof */
+ {0.0f, 0.0f}, {1.0f, 0.0f}, {1.0f, 1.0f}, {0.0f, 1.0f},
+
+ /* Right */
+ {0.0f, 0.0f}, {0.0f, 1.0f}, {1.0f, 1.0f}, {1.0f, 0.0f},
+
+ /* Left */
+ {0.0f, 0.0f}, {0.0f, 1.0f}, {1.0f, 1.0f}, {1.0f, 0.0f}
+};
+
+static GLfloat fogcoord_pointer[][1] = {
+ /* Back */
+ {1.0f}, {1.0f}, {1.0f}, {1.0f},
+
+ /* Floor */
+ {1.0f}, {1.0f}, {0.0f}, {0.0f},
+
+ /* Roof */
+ {1.0f}, {1.0f}, {0.0f}, {0.0f},
+
+ /* Right */
+ {0.0f}, {0.0f}, {1.0f}, {1.0f},
+
+ /* Left */
+ {0.0f}, {0.0f}, {1.0f}, {1.0f}
+};
+#endif
+
+
+static void Display( void )
+{
+ glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+ glLoadIdentity ();
+
+ glTranslatef(0.0f, 0.0f, camz);
+
+#if ARRAYS
+ glDrawElements(GL_QUADS, sizeof(vertex_index) / sizeof(vertex_index[0]), GL_UNSIGNED_INT, vertex_index);
+#else
+ /* Back */
+ glBegin(GL_QUADS);
+ glFogCoordf_ext(1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(-2.5f,-2.5f,-DEPTH);
+ glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 2.5f,-2.5f,-DEPTH);
+ glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 2.5f, 2.5f,-DEPTH);
+ glFogCoordf_ext(1.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-2.5f, 2.5f,-DEPTH);
+ glEnd();
+
+ /* Floor */
+ glBegin(GL_QUADS);
+ glFogCoordf_ext(1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(-2.5f,-2.5f,-DEPTH);
+ glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 2.5f,-2.5f,-DEPTH);
+ glFogCoordf_ext(0.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 2.5f,-2.5f, DEPTH);
+ glFogCoordf_ext(0.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-2.5f,-2.5f, DEPTH);
+ glEnd();
+
+ /* Roof */
+ glBegin(GL_QUADS);
+ glFogCoordf_ext(1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(-2.5f, 2.5f,-DEPTH);
+ glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 2.5f, 2.5f,-DEPTH);
+ glFogCoordf_ext(0.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 2.5f, 2.5f, DEPTH);
+ glFogCoordf_ext(0.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-2.5f, 2.5f, DEPTH);
+ glEnd();
+
+ /* Right */
+ glBegin(GL_QUADS);
+ glFogCoordf_ext(0.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f( 2.5f,-2.5f, DEPTH);
+ glFogCoordf_ext(0.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f( 2.5f, 2.5f, DEPTH);
+ glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 2.5f, 2.5f,-DEPTH);
+ glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 2.5f,-2.5f,-DEPTH);
+ glEnd();
+
+ /* Left */
+ glBegin(GL_QUADS);
+ glFogCoordf_ext(0.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(-2.5f,-2.5f, DEPTH);
+ glFogCoordf_ext(0.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-2.5f, 2.5f, DEPTH);
+ glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f(-2.5f, 2.5f,-DEPTH);
+ glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f(-2.5f,-2.5f,-DEPTH);
+ glEnd();
+#endif
+
+ glutSwapBuffers();
+}
+
+
+static void Reshape( int width, int height )
+{
+ glViewport(0, 0, width, height);
+ glMatrixMode(GL_PROJECTION);
+ glLoadIdentity();
+ gluPerspective(45.0f, (GLfloat)(width)/(GLfloat)(height), 0.1f, 100.0f);
+ glMatrixMode(GL_MODELVIEW);
+ glLoadIdentity();
+}
+
+
+static void Key( unsigned char key, int x, int y )
+{
+ (void) x;
+ (void) y;
+ switch (key) {
+ case 'f':
+ fogMode = SetFogMode(fogMode + 1);
+ break;
+ case '+':
+ if (fogDensity < 1.0 - EPS) {
+ fogDensity += 0.05;
+ }
+ SetFogMode(fogMode);
+ break;
+ case '-':
+ if (fogDensity > EPS) {
+ fogDensity -= 0.05;
+ }
+ SetFogMode(fogMode);
+ break;
+ case 's':
+ if (fogStart > EPS) {
+ fogStart -= 0.1;
+ }
+ SetFogMode(fogMode);
+ break;
+ case 'S':
+ if (fogStart < fogEnd - EPS) {
+ fogStart += 0.1;
+ }
+ SetFogMode(fogMode);
+ break;
+ case 'e':
+ if (fogEnd > fogStart + EPS) {
+ fogEnd -= 0.1;
+ }
+ SetFogMode(fogMode);
+ break;
+ case 'E':
+ if (fogEnd < 1.0 - EPS) {
+ fogEnd += 0.1;
+ }
+ SetFogMode(fogMode);
+ break;
+ case 'c':
+ fogCoord = SetFogCoord(fogCoord ^ GL_TRUE);
+ break;
+ case 27:
+ exit(0);
+ break;
+ }
+ glutPostRedisplay();
+}
+
+
+static void SpecialKey( int key, int x, int y )
+{
+ (void) x;
+ (void) y;
+ switch (key) {
+ case GLUT_KEY_UP:
+ if (camz < (DEPTH - 1.0)) {
+ camz += 1.0f;
+ }
+ break;
+ case GLUT_KEY_DOWN:
+ if (camz > -19.0) {
+ camz -= 1.0f;
+ }
+ break;
+ }
+ glutPostRedisplay();
+}
+
+
+static void Init( void )
+{
+ have_fog_coord = glutExtensionSupported("GL_EXT_fog_coord");
+
+ if (BuildTexture(TEXTURE_FILE, texture) == -1) {
+ exit(1);
+ }
+
+ glEnable(GL_TEXTURE_2D);
+ glClearColor(0.0f, 0.0f, 0.0f, 0.5f);
+ glClearDepth(1.0f);
+ glDepthFunc(GL_LEQUAL);
+ glEnable(GL_DEPTH_TEST);
+ glShadeModel(GL_SMOOTH);
+ glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
+
+ glFogfv(GL_FOG_COLOR, fogColor);
+ glHint(GL_FOG_HINT, GL_NICEST);
+ fogCoord = SetFogCoord(GL_TRUE); /* try to enable fog_coord */
+ fogMode = SetFogMode(2); /* GL_EXP */
+
+ camz = -19.0f;
+
+#if ARRAYS
+ glEnableClientState(GL_VERTEX_ARRAY);
+ glVertexPointer(3, GL_FLOAT, 0, vertex_pointer);
+
+ glEnableClientState(GL_TEXTURE_COORD_ARRAY);
+ glTexCoordPointer(2, GL_FLOAT, 0, texcoord_pointer);
+
+ if (have_fog_coord) {
+ glFogCoordPointer_ext = (GLFOGCOORDPOINTEREXTPROC)glutGetProcAddress("glFogCoordPointerEXT");
+ glEnableClientState(GL_FOG_COORDINATE_ARRAY_EXT);
+ glFogCoordPointer_ext(GL_FLOAT, 0, fogcoord_pointer);
+ }
+#endif
+}
+
+
+int main( int argc, char *argv[] )
+{
+ glutInit( &argc, argv );
+ glutInitWindowPosition( 0, 0 );
+ glutInitWindowSize( 640, 480 );
+ glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH );
+ glutCreateWindow(argv[0]);
+ glutReshapeFunc( Reshape );
+ glutKeyboardFunc( Key );
+ glutSpecialFunc( SpecialKey );
+ glutDisplayFunc( Display );
+ Init();
+ glutMainLoop();
+ return 0;
+}
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