message: Hack to fix pixelOps in the DFB
  TODO: We need to better handle the MasterTileMessages so we can just
  send SoA tile data instead of AoS like we have to convert to now, and
  store in the TileData::color member
diff: @@ -448,6 +448,20 @@ void DFB::processMessage(AllTilesDoneMessage *msg, ospcommon::byte_t* data)
  if (pixelOp) {
  pixelOp->postAccum(tile->final);
  + if (colorBufferFormat == OSP_FB_RGBA8 || colorBufferFormat == OSP_FB_SRGBA) {
  + uint8_t *colors = reinterpret_cast<uint8_t*>(tile->color);
  + for (size_t i = 0; i < TILE_SIZE * TILE_SIZE; ++i) {
  + colors[i * 4] = clamp(tile->final.r[i] * 255.0, 0.0, 255.0);
  + colors[i * 4 + 1] = clamp(tile->final.g[i] * 255.0, 0.0, 255.0);
  + colors[i * 4 + 2] = clamp(tile->final.b[i] * 255.0, 0.0, 255.0);
  + colors[i * 4 + 3] = clamp(tile->final.a[i] * 255.0, 0.0, 255.0);
  + }
  + } else if (colorBufferFormat == OSP_FB_RGBA32F) {
  + for (size_t i = 0; i < TILE_SIZE * TILE_SIZE; ++i) {
  + tile->color[i] = vec4f(tile->final.r[i], tile->final.g[i],
  + tile->final.b[i], tile->final.a[i]);
  + }
  + }
  }
  auto msg = [&]{
  