Function SetupSky

Descent3/terrain.cpp:674–792

Compute a parametric sphere for our sky.

// Compute a parametric sphere for our sky.
void SetupSky(float radius, int flags, uint8_t randit) {
  int jump = 65536 / MAX_HORIZON_PIECES;
  int top = ((65536 / 4) * 3) + (65536 / 8);

  int i, t;

  Terrain_sky.radius = radius;
  Terrain_sky.flags = flags;

  int horizon_r = GR_COLOR_RED(Terrain_sky.horizon_color);
  int horizon_g = GR_COLOR_GREEN(Terrain_sky.horizon_color);
  int horizon_b = GR_COLOR_BLUE(Terrain_sky.horizon_color);

  float rad_diff = radius - SKY_RADIUS;

  // Figure out where our points in the inside of the sphere are
  for (i = 0; i < 6; i++) {
    const int increment = 16384 / 5;
    const angle pitch = (65536 - 16384) + (i * increment);

    for (t = 0; t < MAX_HORIZON_PIECES; t++) {
      vector *vec = &Terrain_sky.horizon_vectors[t][i];

      matrix tempm;
      vm_AnglesToMatrix(&tempm, pitch, t * jump, 0);
      vm_ScaleVector(vec, &tempm.fvec, SKY_RADIUS / 2);

      vec->y -= MAX_TERRAIN_HEIGHT;
      vec->y += (rad_diff / 4);
    }
  }

  // Now figure out texture UVS
  for (i = 0; i < 5; i++) {
    float scalar = (float)i / 4.0;
    int angle_increment = 65536 / MAX_HORIZON_PIECES;
    for (t = 0; t < MAX_HORIZON_PIECES; t++) {
      float cur_sin = FixSin(t * angle_increment) * scalar;
      float cur_cos = FixCos(t * angle_increment) * scalar;

      cur_sin = (cur_sin + 1) / 2;
      cur_cos = (cur_cos + 1) / 2;

      Terrain_sky.horizon_u[t][i] = cur_cos;
      Terrain_sky.horizon_v[t][i] = cur_sin;
    }
  }

  int highcount = 0; // keep track of what stars are close to the top of the sphere
                     // don't draw too many of them
  if (!randit)
    return;

  for (i = 0; i < MAX_STARS; i++) {
    vector starvec;
    matrix tempm;
    int p;
    top = ((65536 / 4) * 3);