--- /dev/null
+#include <GL/glut.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <math.h>
+
+#define TEXRES_X 256
+#define TEXRES_Y 256
+
+unsigned char env_map[TEXRES_X][TEXRES_Y][4];
+GLuint texName;
+float window_x = 640, window_y = 480;
+float alpha = 0.0, beta = 0.0;
+
+ /*****************************************************************/
+ /*****************************************************************/
+ /*****************************************************************/
+void setColor(float x, float y, float z, float angular_size, float r, float g, float b, float a)
+{
+ //normalize
+ float inv_length = 1.0 / sqrt(x*x + y*y + z*z);
+ x *= inv_length; y *= inv_length; z *= inv_length;
+ printf("x = %f, y = %f, z = %f\n", x, y, z);
+
+ float cos_angular_size = cos(angular_size*3.1415/180.0);
+ printf("cos_angular_size = %f\n", cos_angular_size);
+
+ for(float tz_sign = -1.0; tz_sign < 3.0; tz_sign += 2.0)
+ {
+ for(float tx = -1.0; tx <= 1.0; tx += 0.01)
+ {
+ for(float ty = -1.0; ty <= 1.0; ty += 0.01)
+ {
+ if ((1.0 - tx*tx - ty*ty)<0.0)
+ continue;
+
+ float tz = tz_sign * sqrt(1.0 - tx*tx - ty*ty);
+
+ float cos_phi = x*tx + y*ty + z*tz;
+
+ if (cos_angular_size < cos_phi)
+ {
+ float rx = tx; //mirroring on the z=0 plane
+ float ry = ty;
+ float rz = -tz;
+
+ float inv_m = 1.0 / (2.0 * sqrt(rx*rx + ry*ry + (rz + 1)*(rz + 1)));
+ int s = TEXRES_X * (rx * inv_m + 0.5);
+ int t = TEXRES_Y * (ry * inv_m + 0.5);
+
+ //seg_fault protection:
+ if (s<0) s=0;
+ if (s>=TEXRES_X) s=TEXRES_X-1;
+
+ if (t<0) t=0;
+ if (t>=TEXRES_Y) t=TEXRES_Y-1;
+
+ env_map[s][t][0] = r * 255;
+ env_map[s][t][1] = g * 255;
+ env_map[s][t][2] = b * 255;
+ env_map[s][t][3] = a * 255;
+ }
+ }
+ }
+ }
+}
+ /*****************************************************************/
+ /*****************************************************************/
+ /*****************************************************************/
+
+void init(void)
+{
+ glClearColor(0.0, 0.0, 0.0, 0.0);
+ glShadeModel(GL_FLAT);
+ glEnable(GL_DEPTH_TEST);
+
+ for(int x=0; x<TEXRES_X; x++)
+ {
+ for(int y=0; y<TEXRES_Y; y++)
+ {
+ env_map[x][y][0] = x; //a few colors
+ env_map[x][y][1] = y;
+ env_map[x][y][2] = 128;
+ env_map[x][y][3] = 128;
+ }
+ }
+
+ /*****************************************************************/
+ /*****************************************************************/
+ /*****************************************************************/
+ // x y z ang r g b a
+ setColor(0.0, 0.0, -1.0 , 23.0, 1.0, 1.0, 1.0, 1.0);
+ setColor(0.7071067, 0.0, -0.7071067, 23.0, 1.0, 0.0, 0.0, 1.0);
+ /*****************************************************************/
+ /*****************************************************************/
+ /*****************************************************************/
+
+ glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
+ glGenTextures(1, &texName);
+ glBindTexture(GL_TEXTURE_2D, texName);
+
+ glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+ glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+ glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, TEXRES_X, TEXRES_Y, 0, GL_RGBA, GL_UNSIGNED_BYTE, env_map);
+}
+
+void reshape(int w, int h)
+{
+ window_x = w; window_y = h;
+ glViewport(0, 0, (GLsizei) w, (GLsizei) h);
+ glMatrixMode(GL_PROJECTION);
+ glLoadIdentity();
+ gluPerspective((GLdouble) 60.0, ((GLdouble)w)/((GLdouble)h), (GLdouble) 10.0, (GLdouble) 1000.0);
+ glMatrixMode(GL_MODELVIEW);
+ glLoadIdentity();
+ glTranslatef(0.0, 0.0, -20.0);
+}
+
+void display()
+{
+ glClear ( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT ) ;
+
+ //show light
+ glMatrixMode(GL_PROJECTION);
+ glLoadIdentity();
+ gluPerspective((GLdouble) 60.0, window_x/window_y, (GLdouble) 1.0, (GLdouble) 100.0);
+ glMatrixMode(GL_MODELVIEW);
+ glLoadIdentity();
+
+ glTranslatef(0.0, 0.0, -10.0);
+
+ glRotatef(alpha, 1.0, 0.0, 0.0);
+ glRotatef(beta, 0.0, 1.0, 0.0);
+
+ glBegin(GL_LINES);
+ glColor3f(1.0, 1.0, 1.0);
+ glVertex3f(0.0, 0.0, 0.0);
+ glVertex3f(0.0, 0.0, 1.0);
+ glEnd();
+
+ /*****************************************************************/
+ /*****************************************************************/
+ /*****************************************************************/
+ glEnable(GL_TEXTURE_2D);
+ glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
+ glBindTexture(GL_TEXTURE_2D, texName);
+
+ glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_SPHERE_MAP);
+ glTexGeni(GL_T, GL_TEXTURE_GEN_MODE, GL_SPHERE_MAP);
+ glEnable(GL_TEXTURE_GEN_S);
+ glEnable(GL_TEXTURE_GEN_T);
+
+ glBegin(GL_QUADS);
+ glNormal3f(0.0, 0.0, 1.0);
+ glVertex3f(1.0, 1.0, 0.0);
+ glVertex3f(-1.0, 1.0, 0.0);
+ glVertex3f(-1.0, -1.0, 0.0);
+ glVertex3f(1.0, -1.0, 0.0);
+ glEnd();
+
+ glDisable(GL_TEXTURE_GEN_S);
+ glDisable(GL_TEXTURE_GEN_T);
+ glDisable(GL_TEXTURE_2D);
+ /*****************************************************************/
+ /*****************************************************************/
+ /*****************************************************************/
+
+ //show how the map looks like
+ glMatrixMode(GL_PROJECTION);
+ glLoadIdentity();
+ //gluOrtho2D(0.0 -10.0, 1.0 +10.0, -window_x/window_y -10.0,0.0 +10.0);
+ //glOrtho(0.0, 5.0, -5.0, 0.0, -10.0, 10.0);
+ glOrtho(0.0, 5.0*(window_x/window_y), -5.0, 0.0, -10.0, 10.0);
+ glMatrixMode(GL_MODELVIEW);
+ glLoadIdentity();
+ glEnable(GL_TEXTURE_2D);
+ glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
+ glBindTexture(GL_TEXTURE_2D, texName);
+
+ glBegin(GL_QUADS);
+ glTexCoord2f(0.0, 0.0); glVertex3f(0.0, 0.0, 0.0);
+ glTexCoord2f(0.0, 1.0); glVertex3f(0.0, -1.0, 0.0);
+ glTexCoord2f(1.0, 1.0); glVertex3f(1.0, -1.0, 0.0);
+ glTexCoord2f(1.0, 0.0); glVertex3f(1.0, 0.0, 0.0);
+ glEnd();
+ glFlush();
+ glDisable(GL_TEXTURE_2D);
+
+ glutPostRedisplay () ;
+ glutSwapBuffers () ;
+}
+
+void keyboard (unsigned char key, int x, int y)
+{
+ switch(key)
+ {
+ case 27:
+ exit(0);
+
+ case '8':
+ alpha += 1.0;
+ if (alpha >= 360.0) alpha -= 360.0;
+ break;
+
+ case '2':
+ alpha -= 1.0;
+ if (alpha < 0.0) alpha += 360.0;
+ break;
+
+ case '4':
+ beta -= 1.0;
+ if (beta <= -90.0) beta = -90.0;
+ break;
+
+ case '6':
+ beta += 1.0;
+ if (beta >= 90.0) beta = 90.0;
+ break;
+
+ case '5':
+ alpha = 0.0; beta = 0.0;
+ break;
+ }
+}
+
+int main(int argc, char** argv)
+{
+ glutInitWindowSize(window_x, window_y);
+ glutInit(&argc, argv);
+ glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
+ glutCreateWindow(argv[0]);
+ init();
+ glutDisplayFunc(display);
+ glutReshapeFunc(reshape);
+ glutKeyboardFunc(keyboard);
+
+ glutMainLoop();
+
+ return 0;
+}