Very strange problem with baking textures - huge parts of the texture are "missing"


I’m working on a vintage wooden table asset for a game.

I’ve made a lowpoly model, and then sculpted a highpoly model.
I’ve created procedural a wood material, now I’m trying to bake it from my highpoly model to the lowpoly one.

And here’s a problem.

The highpoly model looks as expected in the viewport preview:

But when I bake the textures onto my lowpoly model, there’s large areas of the texture that are completely flat (the plain brown parts):

I’ve tried playing with:
The Baking Ray Distance setting, and my hihgpoly material, but nothing seems to work.
I thought that maybe it’s a result of lowpoly/highpoly meshes intersecting - but the normals should be completely messed up (green) in such places, not just flat - als othe Ray Discance would affect this and it does not. Also: the “flat areas” seem to not coincide with the mesh overlaps at all.

I’m running Blender 2.80 on Manjaro Linux (right now 2019-07-09 22:45 build, but I’m updating often, hoping that this is a bug that’ll be fixed).

Here’s the full Blender project:

Can anybody reproduce this?
How can I bake the textures properly?
Is it something I’m doing wrong or could this be a software bug?

I’ve now baked a texture using a simple Noise node for my high-poly material.

The results are as expected - no flat areas are present:

(nevermind the black dots all around -I’ve added nails to the scene)

This makes my think that there’s a problem in my material - but the problem only shows up when baking the textures.

I think I’m going to try and re-make the material (sigh…).

Here’s the whole node tree for the wood material (you can look it up in the Blend file above):

I’ve tried bypassing parts of the node tree before to find a problematic area, but without any success.

I am not an expert…but all I have ever seen Starts with a High-Poly, then re-topo to a low poly…that way the low poly mesh is snapped to the faces of the High-Poly…from looking at your meshes, and selecting both the High and low poly’s you can see where the High Poly is above the low…and the selection outlines follow what your Baked Texture ends up, with the solid browns…Maybe someone else can get you a better idea, but I would take your Hight-Poly and re-topo to a Low and I bet you bakes will work.

That’s not the only way to do it. I’ve seen people doing it the other way around. What I did for this model is started with a lowpoly, then creating a highpoly mesh, sculpted it for detail, then used remesh and decimation modifiers to create a lowpoly mesh based on that.

Actually - I checked that and the brown areas are not defined by the intersection of both meshes.

Also - I’ve re-did the wood material from scratch and it bakes fine now, without any change to the geometry (apart from adding the nails as separate objects). This is the final result - lowpoly with baked textures, rendered in Eevee:

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I see…but you did create the Low Poly from the High poly even if you were starting with a Low poly…and that was what I was getting at. Glad that the new textures work for you!