Hard Surface Retopology - Making sense of planar quads

Reil

Hi guys,

I'm kinda new here (lurking for a bit, thank you for a lot of useful information).

I'm modeling a toaster for a kitchen scene, and I'm stuck in the retopology phase. I used the modeling toolkit of Maya to create the low poly mesh. The final result wasn't perfect, and my mentor said that there were non-planar surfaces that were screwing the normal map.
Using clean up I noted that about 80% was non planar so he asked me to make it again.

I'm trying to figuring out the best way to retopology an hard surface in Maya, without using 3D Coat/Topogun or other software for now.
Scaling a quad on the z-axis to 0% make the quad planar, but the near quads are affected so they become non-planar. So...should I bother to make them all planar? How will this affect the normal map?


Base Retopo (orange faces are non planar)

Thank you for your help!

oglu

just model a new one... most of the time you are faster... retopo for hardsurface is not a good way to do it...

Reil

I've seen a few tutorial explaining retopo for hard surface in Blender or zBrush... Can I ask you why it isn't a good way ?

WarrenM

I think he's talking auto-retopo. Most of the time, on hard surface stuff, you spend more time cleaning up what the auto-retopo did than you would have just modeling a fresh low poly from scratch.

oglu

no im talking about retopo for hard surface by hand...
most of the time its faster to remodel the shape... clicking with a retopo tool onto the surface leads often to to even meshes... you loose a lot of the hard edged stuff...

it depends on the model but what i see from the picture above i would remodel it by hand...

Reil

This is the hi-poly, I splitted it to bake it separately: http://take.ms/zlIQV

recreating a low poly shape from scratch and make it stick near the hi poly wouldn't create the same mistakes? Maybe a little less but...
as a rule I found "less polys you got, the less planar they are." on another thread. So where can I accept non planar in my low poly?

Eric Chadwick

Who the hell is telling you to avoid non-planar polys? They have no clue what they're talking about.

All your normal map baking tool cares about are triangles. You should be triangulating the model before baking, to prevent auto-triangulation differences between the baking software and your final display software.

Reil

Actually I asked again and he wasn't telling me to prevent non planar for the whole model but as much as possible.

I'm going to look a bit about triangulating before baking, every tutorial I watched about baking didn't say anything about triangulate the meshes...

edit: here was the problem with non planar face when imported in Unity
http://monosnap.com/file/iI2Fc2YaR7JATmgSwIwc1iamHCM0QC

Eric Chadwick

Yeah, this is exactly why you need to triangulate. We have more here on the "why"
http://wiki.polycount.com/wiki/Polygon_Count#Polygons_Vs._Triangles
http://wiki.polycount.com/wiki/Texture_Baking#Triangulation

The other reason to triangulate is to avoid errors between baking a normal map and displaying the normal map on your model. If the internal edges are different, the shading will be messed up.

WarrenM

It's amazing how many artists aren't aware they need to triangulate BEFORE baking. I've spoken with some very experienced people who looked at me like I had a third eye.

m4dcow

WarrenM wrote: »

It's amazing how many artists aren't aware they need to triangulate BEFORE baking. I've spoken with some very experienced people who looked at me like I had a third eye.

I think it's dumb luck really, that the baker happens to triangulate the same way the app might so things just happen to line up.

WarrenM

And then there's that head slap moment where they're like, "Oh, THAT'S why I get those weird artifacts sometimes!"

Yep.

Neox

Well the problem is auto triangulation in tools like Maya, where you have no control over the inner edges, in Max the triangulation is always locked, even tho the inner edges are not visible. They will not change randomly. Random/automatic triangulation is the pest, just horrible to work with, be it skinning or just iteration.
Having no control over convex/concave faces or destructive triangulation is in general just shitty for any game productions.

Eric Chadwick

It's not strictly locked in Max though. If you move verts around, even just slightly adjusting a square-ish quad, then Editable Poly will re-arrange the interior edges to maintain what it considers to be good triangulation. Shortest distance I think.

Neox

Eric Chadwick wrote: »

It's not strictly locked in Max though. If you move verts around, even just slightly adjusting a square-ish quad, then Editable Poly will re-arrange the interior edges to maintain what it considers to be good triangulation. Shortest distance I think.

Since when? Interior edges are locked for me until I change them. If thats one of the additions of newer versions it is absolutely horrible and removes the sense in the turn edge option

DireWolf

Reil wrote: »

This is the hi-poly, I splitted it to bake it separately: http://take.ms/zlIQV

recreating a low poly shape from scratch and make it stick near the hi poly wouldn't create the same mistakes? Maybe a little less but...
as a rule I found "less polys you got, the less planar they are." on another thread. So where can I accept non planar in my low poly?

If I have to clean that piece, I'd select edge myself and do delete edge loop. Looks easier that way since your original topology wasn't all that bad to begin with.

Eric Chadwick

Yeah, interior edges are locked if you turn them. But the OP like many others was blissfully unaware of the option. None of their edges are set, and thus are fluttering like butterflies.

Neox

Eric Chadwick wrote: »

Yeah, interior edges are locked if you turn them. But the OP like many others was blissfully unaware of the option. None of their edges are set, and thus are fluttering like butterflies.

I will test again but i would swear the edges stay the same after they are created, no matter what you do to the polygon

Eric Chadwick

Hmmm, I was wrong, turning an edge doesn't fix it in place. The edges do move around.

Make a plane with no subdivisions, convert it to Editable Poly, and move the opposite corners up a bit. Switch the viewport to Facets. Move one of the corners so it overlaps the interior edge, and the edge flips.

I don't think this happens if you're making subtle changes though, so that's good at least.



Max 2015.

Neox

Eric Chadwick wrote: »

Hmmm, I was wrong, turning an edge doesn't fix it in place. The edges do move around.

Make a plane with no subdivisions, convert it to Editable Poly, and move the opposite corners up a bit. Switch the viewport to Facets. Move one of the corners so it overlaps the interior edge, and the edge flips.

I don't think this happens if you're making subtle changes though, so that's good at least.



Max 2015.

interesting, i guess i always triangulate such extremes by habit, i tried a lot with noises and all and couldn't reproduce that edge flipping but i never went that extreme, it's a behaviour i only knew from maya as it can happen with the slightest changes