Hi, a few things:
- Primitive Render Mode is set to “Render Scene Primitives (Legacy)” (try a different mode because this is a legacy mode and may be processing the AA differently and with lower quality than another mode…test it by itself first, without changing anything else)
- Enable “Capture Every Frame” and disable “Capture Movement”
- Disable “Include Actor for HLOD Mesh Generation” (do it separately from the other changes, so test the previous changes first)
- In the MirrorRenderTarget editor, the Imported Size (2048 x 2048) is different from the Displayed Size (4096 x 2048). Is it possible to re-import at the same size as displayed size? It could be a source of skewing pixels for the render target image, thus causing such horrible aliasing.
- Instead of selecting NoMips, select “From TextureGroup”, and then below the setting for that, select a different Texture Group than RenderTarget. If it doesn’t work, select RenderTarget again as TextureGroup, then select “Leave Existing Mips” in Mip Gen Settings.
- You changed Min Lightmap Resolution, when what needs to be changed is actual Lightmap Resolution. It’s further down in the mesh editor settings, and needs to be the same or higher than Min Lightmap Resolution. Min LR is the lowest LR that’d be applied, but isn’t the actual LR applied in all cases (such as for LOD levels). Simply ensure that Min LR is lower than actual LR (whether in the mesh editor, or in the object’s details panel setting which is called Override). It should be alright at 256 or 512, with Min LR set at 128 or 256.
Try those things and see how it goes. It’s a process of elimination approach in a way, so try each separately, and if it doesn’t work, change back to what it was and try the next potential fix. After they’re all tried separately, then try in combination. A more experienced and knowledgeable person may chime in and know exactly what to do, but until then I suggest trying those.