Hey simmania,
I received some important information about changing the resolution of your Render Textures at runtime. The results you are seeing is to be expected and here is why.
Whenever you create a Render Target the overall resolution, whatever you choose to set it to, is stored in memory and allocated for that specific size. How render targets function is they are constantly being called upon to update in Realtime.
By setting the resolution to higher or lower value at runtime, the space that was allocated for the texture is changed and not referenced correctly. It then needs to create a new space for the given resolution (in memory) and store that value. Returning back to the original resolution after changing means you have now broken up the integrity of rendering code and left ‘gaps’ or empty unused areas.
This is why we suggest not changing the resolution at runtime, but rather creating two Render Targets with the desired resolutions to be changed at specific distances or times. This allows the Engine to allocate space for both textures so when switching between the two, there are no performance issues like the one you are experiencing.
I hope this gave you some insight as to why you are experiencing the issue, but if you would like some more information or additional assistance I will be happy to help.
Cheers,