Function DeformTerrainPoint

Descent3/terrain.cpp:385–458

Changes the terrain mesh for deformation effect

// Changes the terrain mesh for deformation effect
void DeformTerrainPoint(int x, int z, int change_height) {
  terrain_segment *tseg = &Terrain_seg[z * TERRAIN_WIDTH + x];
  int i;

  change_height += tseg->ypos;

  change_height = std::clamp(change_height, 0, 255);

  tseg->ypos = change_height;
  tseg->y = tseg->ypos * TERRAIN_HEIGHT_INCREMENT;

  int sx = std::max(0, x - 1);
  int sz = std::max(0, z - 1);

  // Update min/max
  for (i = 0; i < 7; i++) {
    int row_width = 1 << i;
    int div = 256 >> i;

    for (int t = sz; t <= z; t++) {
      for (int k = sx; k <= x; k++) {

        int offset = ((t / div) * row_width) + (k / div);

        if (tseg->ypos > Terrain_max_height_int[i][offset])
          Terrain_max_height_int[i][offset] = tseg->ypos;
        if (tseg->ypos < Terrain_min_height_int[i][offset])
          Terrain_min_height_int[i][offset] = tseg->ypos;
      }
    }
  }

  // Update normals

  for (i = sz; i <= z; i++) {
    for (int t = sx; t <= x; t++) {
      vector a, b, c;
      terrain_segment *tseg0 = &Terrain_seg[i * TERRAIN_WIDTH + t];
      terrain_segment *tseg1 = &Terrain_seg[(i + 1) * TERRAIN_WIDTH + t];
      terrain_segment *tseg2 = &Terrain_seg[((i + 1) * TERRAIN_WIDTH) + t + 1];
      terrain_segment *tseg3 = &Terrain_seg[(i * TERRAIN_WIDTH) + t + 1];

      // 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 + 1) * TERRAIN_SIZE;

      c.x = (t + 1) * TERRAIN_SIZE;
      c.y = tseg2->y;
      c.z = (i + 1) * TERRAIN_SIZE;

      vm_GetNormal(&TerrainNormals[MAX_TERRAIN_LOD - 1][i * TERRAIN_WIDTH + t].normal1, &a, &b, &c);

      // Now do lower right triangle