Today I was working on a problem with impostor texture streaming in UE4. I was not satisfied with the possibility of disabling the streaming for those textures, because they are quite large. I also found out that generating material streaming information does not work properly, because it reads GameThreadShaderMap that, as the comment states, is loaded from cooked assets and not available in the editor. This is a topic for further investigation, though. Meanwhile my solution was to modify FStreamingTexture::GetExtraBoost function, adding a branch for impostor texture groups with a boost value of 16.
I found some useful console variables and a command during the process. Here they are:
r.Streaming.DropMips 2 - disables mip map caching, not needed mip levels will be unstreamed immediately r.Streaming.FullyLoadUsedTextures 1 – forces loading of an entire mip chain r.Streaming.Boost <value> - global wanted texture size multiplier InvestigateTexture <texture name> - displays streaming information for a texture in a console window, most notably the highest loaded mip level