message: Actually write the multisampled alpha
diff: @@ -116,11 +116,11 @@ unmasked void Renderer_default_renderTile(uniform Renderer *uniform self,
  self->renderSample(self,perFrameData,screenSample);
  col = col + screenSample.rgb;
  - alpha = alpha + screenSample.alpha;
  + alpha += screenSample.alpha;
  }
  col = col * (spp_inv);
  - alpha = alpha * (spp_inv);
  - setRGBAZ(tile,pixel,col,screenSample.alpha,screenSample.z);
  + alpha *= spp_inv;
  + setRGBAZ(tile,pixel,col,alpha,screenSample.z);
  }
  } else {
  if (tile.accumID >= 0) {
  