Backing a flat surface into a smooth low-poly model?

cubrman

I am a newbie in 3d and I am trying to figure out how to properly make hard surface high-poly meshes.

I am struggling to bake a flat surface onto a smooth-normals low poly mesh even with the most basic setup (a quad).

This is my low poly:


This is my high poly:


Both models have smooth shading on all polygons. High poly looks absolutely flat in blender and has two supporting edge loops near every face.

And this is how shading looks on the low poly model after the hq bake in Substance Painter:

It might be a bit hard to see, but when you move the camera, it becomes evident, that the door surface is x-shaped with a protrusion in the center. Is there any way to bake an absolutely flat surface onto a polygon with smooth shading?

Justin Meisse

Make the edges hard on your low poly and make sure you split the uv islands as well. This tutorial from Marmoset will explain things better:
https://www.marmoset.co/posts/toolbag-baking-tutorial/?page=Best%20Results#bestresults

If you want to see what's happening, in Substance Painter switch your view mode to "solo" and "normal + height + base normal" you'll see that the normal map is struggling against the smoothing groups on your model.

cubrman

Huge thanks for the link.

After a number of experiments and reading a few articles I came to a conclusion that you cannot bake absolutely flat normals onto a smooth 8-sided quad (to preserve smooth edges). You absolutely have to have edge loops separating flat sections from smooth ones. Or just double edge loops to solve the problem without the need for the high poly model.

Justin Meisse

Here's a quick example I tossed together in substance painter. I was going to whip up an example in Toolbag 3, but they both looked pretty nice. You should give Marmoset Toolbag 3 a try, it's become my defacto baker now.

Neox

now compress the normalmap on the soft mesh