Function BuildTerrainNormals

Descent3/terrain.cpp:534–589

Builds normals for the currently loaded terrain

// Builds normals for the currently loaded terrain
void BuildTerrainNormals() {
  int i, t, l, z, x;
  vector a, b, c;
  int simplemul;
  vector up_norm = {0, 1.0, 0};

  // Set all to be initially up
  for (i = 0; i < TERRAIN_WIDTH * TERRAIN_DEPTH; i++) {
    TerrainNormals[MAX_TERRAIN_LOD - 1][i].normal1 = up_norm;
    TerrainNormals[MAX_TERRAIN_LOD - 1][i].normal2 = up_norm;
  }

  for (l = MAX_TERRAIN_LOD - 1; l < MAX_TERRAIN_LOD; l++) {
    simplemul = 1 << ((MAX_TERRAIN_LOD - 1) - l);

    for (z = 0, i = 0; i < TERRAIN_DEPTH - simplemul; i += simplemul, z++) {
      for (x = 0, t = 0; t < TERRAIN_WIDTH - simplemul; t += simplemul, x++) {
        terrain_segment *tseg = &Terrain_seg[i * TERRAIN_WIDTH + t];
        terrain_segment *tseg0 = &Terrain_seg[i * TERRAIN_WIDTH + t];
        terrain_segment *tseg1 = &Terrain_seg[(i + simplemul) * TERRAIN_WIDTH + t];
        terrain_segment *tseg2 = &Terrain_seg[((i + simplemul) * TERRAIN_WIDTH) + t + simplemul];
        terrain_segment *tseg3 = &Terrain_seg[(i * TERRAIN_WIDTH) + t + simplemul];

        // Do upper left triangle
        a.x = t * TERRAIN_SIZE;
        a.y = tseg0->y;
        a.z = i * TERRAIN_SIZE;

        b.x = t * TERRAIN_SIZE;
        b.y = tseg1->y;
        b.z = (i + simplemul) * TERRAIN_SIZE;

        c.x = (t + simplemul) * TERRAIN_SIZE;
        c.y = tseg2->y;
        c.z = (i + simplemul) * TERRAIN_SIZE;

        vm_GetNormal(&TerrainNormals[l][z * (TERRAIN_WIDTH / simplemul) + x].normal1, &a, &b, &c);

        // Now do lower right triangle
        a.x = t * TERRAIN_SIZE;
        a.y = tseg0->y;
        a.z = i * TERRAIN_SIZE;

        b.x = (t + simplemul) * TERRAIN_SIZE;
        b.y = tseg2->y;
        b.z = (i + simplemul) * TERRAIN_SIZE;

        c.x = (t + simplemul) * TERRAIN_SIZE;
        c.y = tseg3->y;
        c.z = (i)*TERRAIN_SIZE;

        vm_GetNormal(&TerrainNormals[l][z * (TERRAIN_WIDTH / simplemul) + x].normal2, &a, &b, &c);
      }
    }
  }
}

void GenerateTerrainLight() {