Baked height map problem

[Zhivko]

Hi guys!

I'm having an issue with the height map baker. When the height map is baked for some reason it is not smooth. It looks like the polygons from the low poly mesh are projected onto it. I've tried with different meshes, but the result is always the same.
Please take a look at the screenshot.

Thank you!

Zhivko

[sprqst]

Too bad there hasn't been a reply : / I'm having the exact same issue. OP, if you figured out a solution, be great if you can share. Thanks.

[Esger van der Post]

A heightmap shows the difference in height between the low poly and high poly. Since the low poly has sharp edges, the inverse of these edges will appear in your heightmap. So these results are correct.

To illustrate:

[staughost]

Even tho these results are correct can they be used as displacement map? I was not successful in using it as displacement.

[Esger van der Post]

It will only work if you know the correct amount of displacement, but I also don't know how to find this.

[justaviking]

A heightmap shows the difference in height between the low poly and high poly. Since the low poly has sharp edges, the inverse of these edges will appear in your heightmap. So these results are correct.

To illustrate:
>>>  See picture in original post <<<

Brilliant and crystal-clear explanation.  Thank you! 

[sprqst]

Thanks for the explanation, Eggfruit. That makes sense when you put it that way. It's interesting that the displacement maps I've generated from ZBrush in the past don't look like that though ... though after your explanation, I'd expect them to and that would make sense.

As for the exact amount of height to produce an identical result as the high poly mesh, I've wondered about that also. For Displacement maps from ZBrush, for example, we know exactly how to set it up in our renderers so that we know we're getting exactly what the high poly mesh looks like. I've wondered why we don't have that kind of precision when using a height map in SD.

[Esger van der Post]

I haven't worked much with Zbrush so I'm not sure why your results are different. Zbrush may have some wacky options I don't know about :p. Or perhaps the effect was to subtle to notice in previous cases.

Anyway, for consistent offset values, make sure normalization is turned off (Red), and you always write down or just use the same numbers for your front and rear values (blue). (Your values may be very different btw, I just did a quick test without checking the scale of my object)

[sprqst]

Thanks for that Eggfruit. So ... here's the problem that I'm having (that I also think the OP and at least one other recent post that I've seen are having) in pics:
Pic 1: Low Poly mesh
Pic 2: Hi Poly mesh
Pic 3 and 4: the low poly mesh with the Normal and Height map applied (two pics b/c I broke it up into UDIMs, just b/c I'm figuring out the UDIM workflow also)

As you can see, in Pics 3 and 4, there's an imprint of the low polys from the low poly mesh. Also, there are peaks and valleys on the surface of the letters/numbers carved; their surfaces are not smooth as in the high poly model. I can't seem to figure out what I'm doing wrong or how to get rid of these imprints and get these Normal and Height maps generated properly. Any input would be so, so much appreciated. Thanks in advance.

[sprqst]

Ok, so I softened the edges of the low poly model in Maya. That seems to have helped ... together with what Eggfruit said in his/her post (highlighted in blue) ... Thanks for that!! So like he/she posted, it seems that if you use the same number in the Frontal and Rear Value, and then enter this number into your Tessellation scale, then you get what you'd expect to see (at least it worked for me).

If anyone can confirm the importance of softening edges in the imported low-poly model (and any other  details related that maybe a newbie like me should be aware of), that'd be great.

And thank you Eggfruit and others (another poster, Cyrille, I think, pointed me to this post) ... your input seriously is a lifesaver and your sharing is very much appreciated.

[Cyrille Damez]

If anyone can confirm the importance of softening edges in the imported low-poly model (and any other  details related that maybe a newbie like me should be aware of), that'd be great.

Yes, you should soften the edge in the low poly model as long as the "Average Normals" baking option is checked (and it should be in most cases).

[sprqst]

Thanks, Cyrille.

[sprqst]

Ok, so I thought it was solved. But on a closer look, even though I smoothed the low and high poly meshes (softened edges; export with smoothing groups on; tried both FBX and OBJ), I'm still getting 'lumpy' results. The imprint of the low poly isn't explicitly clear like it was before, but the result is still lumpy. I'm playing with different frontal/rear values, but not getting anything that works. If any more insight, would be great. Thanks.

Pic 1: The High Poly Mesh (what the low poly should look like after the Normal and Height are applied)
Pic 2: what the Low Poly is actually looking like (lumpy : / )

p.s. - Here is a link to the low and high poly meshes in case anyone would like and be kind enough to test them:
https://we.tl/t-e4w41GtH5r

[Esger van der Post]

Looks to me like either your heightmap isn't being displayed or your tesselation factor is too low.

To make sure all outputs are being displayed, right click the background of your graph and select "View outputs in 3D view"
You can turn up tesselation in your 3D view menu in Materials>"material name">Edit. You can manually type in a higher number if 16 isn't enough.

[sprqst]

I have tessellation up to 12 (tried even 16 and 64; didn't help) and the height map set to the same amount I used in the frontal/rear values when baking (again, thx for that input, Eggfruit ... I think that's a key thing to know). I even tried bumping up the height amount, but the parts where it's not working are still there.

*On looking at my mesh, it seems that the most extreme problem is maybe happening where there are nonplanar quads in the original mesh. I'm looking into this more and seeing if that is what is affecting the bake (reading some places that it's better to triangulate the mesh before importing into Substance ... ?). In the mean time, if anyone knows that nonplanar quads cause an issue and are something to watch for in baking, that'd be great input in helping to figure this out.

I'll report what I find ...