WMO/Loading

As is frequently the case with Blizzard's various model formats, depending on format versions and flags, some WMO data can be modified when it is read from disk.

When implementing a renderer, these load-time manipulations are important to understand and recreate to ensure correct rendering.

This page attempts to catalog known manipulations that happen prior to rendering.

Color Adjustments

CMapObjGroup::FixColorVertexAlpha

When loading a CMapObjGroup, if SMOHeader->flags 0x8 is not set, a vertex color adjustment routine called FixColorVertexAlpha is run against all vertex colors present in colorVertexList.

if ((this->parent->header->flags & 0x8) == 0) {
  CMapObjGroup::FixColorVertexAlpha(this);
}

The logic is taken from build 3.3.5.12340. Later versions of the function may involve SMOHeader->ambColor and slightly different logic.

void CMapObjGroup::FixColorVertexAlpha(CMapObjGroup *this) {
  int firstNonTransIndex;

  if (this->transBatchCount > 0) {
    firstNonTransIndex = this->batchList[this->transBatchCount - 1]->maxIndex + 1;
  } else {
    firstNonTransIndex = 0;
  }

  if (this->colorVertexCount) {
    for (int i = 0; i < this->colorVertexCount; i++) {
      CImVector *color = &this->colorVertexList[i];

      // Adjust color in int or ext batch
      if (i >= firstNonTransIndex) {
        uint32_t r = (color->r + (((uint32_t)color->a * color->r) / 64)) / 2;
        uint32_t g = (color->g + (((uint32_t)color->a * color->g) / 64)) / 2;
        uint32_t b = (color->b + (((uint32_t)color->a * color->b) / 64)) / 2;

        color->r = r > 255 ? 255 : r;
        color->g = g > 255 ? 255 : g;
        color->b = b > 255 ? 255 : b;

        color->a = 255;
      // Adjust color in trans batch
      } else {
        color->r /= 2;
        color->g /= 2;
        color->b /= 2;
      }
    }
  }
}