Render To Texture Normal Map Issues

[Anonymous]

Hello,

I am getting a strange issue in my normal map when using render to texture. To explain whats going on:

Picture two is of a 'metal framework' for part of a model, for baking purposes I have exploded the model but the picture shows the relevant area, the selected faces shown (but in ALL areas of the model) get this weird oval error in the normal map. There is nothing else in the cage, they are flat planar surfaces. The high poly for this model is essentially the same as the low poly but with every edge box chamfered with the settings 0.5, 2 and 0.5 for a slight rounding on all edges, that is all.

Because the error occurs on every single piece I can't even copy/paste it over the affected area.

I first got this error rendering as an 8k TGA.

This weekend, I rebuilt the entire low poly (which took forever including UV'ing), doing test renders as I went at 1k, and had no issues. Even near completion of the remodel there were no errors so I continued until I had finished.

Overnight I rendered an 8k PNG Normal map with the new low poly version. This resulted in a normal map that was free from the above error, but the normal itself was very weak and faded and looked awful on the model. So I tried re-rendering as a TGA and now I have the full vibrant normal, but with all the errors back.

I tried additional test renders at 1k, with no errors, and 2k with the errors returning. I also tried quickly rebuilding the high poly to no avail.

I asked on polycount forums and was told to change the ray casting or use a cage. I am already using a cage and there is nothing else in the affected regions, these are flat geometry with chamfered edges. I was also told the UV is massively inefficient, but I don't see how else I can unwrap these individual posts. I don't want them stacked because I'm looking to avoid obvious texture repeats.

Can anyone explain why I'm getting this and how to fix it?

The only thing I can think of is that there's some sort of colour or memory limit I'm exceeding in the TGA. Or an element limit in the UVW?

[Noren2]

The "very weak and" faded part might be due to gamma. As for the artifacts, are you sure you've only changed the mentioned parameters? Because that would be strange indeed and likely a bug, but I haven't used the new Render to Texture so far.

The artifacts absolutely look like you are catching the backsides of some polygons, but perhaps your vertex normals are messed up somehow? Is the grey render one with the normals applied or either the "high" or lowpoly base? Because then the smoothing/normals would look strange to begin with and with the many angles meeting, the interpolation between the vertex normals will lead to some strange outcomes and the normal map would have to do some heavy lifting. It should still be possible, but it might makes sense to split that up a bit and use at least a smoothing group for each uv island (as they are split up anyway).

Any chance the artifacts don't show up on lower resolution renders because they are too small for that?

Also I'd have to agree that mapping that fence uniquely seems like a waste, you could spread around a couple of identical elements in a way that would make repetitions pretty hard to spot, plus they have shown you some alternative approaches in that thread that would make more sense.