Full Version: MOI mesh export issue

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Hi PaQ, there isn't a limit on number of points but it does a test that the centroid triangulation won't make a mess.

That happens in UV space and it's pretty simple. For every edge of the n-gon, make a triangle out of the centroid point and the edge points and calculate the signed area of the triangle. If the area is negative it means that triangle is reversed in orientation so don't do a centroid triangulation on that n-gon.

Signed area of a 2D triangle goes like this:

With 2D points K, L, M

XLK =   L.x - K.x;
XMK = M.x - K.x;
YLK =   L.y - K.y;
YMK = M.y - K.y;

signed_area = 0.5 * (XLK*YMK - XMK*YLK);

The sign will be negative if the triangle vertices are in clockwise order, positive if counter-clockwise.

ref:
A programmer's geometry pg. 62
Adrian Bowyer, John Woodwark
Page 62, chapter 4.1 "Area of a triangle"

You can leave out the * 0.5 in this case since it doesn't actually need the area, it just needs to know if it's positive or negative.

- Michael

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Oh nice, thanks for the explanation, I will try to apply that logic !

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@PaQ Hereby is fragment of MOI's (sic!) preview. Rotated triangles almost 90 degree are scattered everywhere. I can't blame my Max's importer here - Its a classic GIGO case.
The default fbx export settings delivers pretty high poly count, so we cant say its because of being low poly.

Image Attachments:
paq.png 

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Hello,

Sorry it's hard to understand what area/model you are pointing with that last screenshot. Since using centroid triangulation I can't find any of those 90 degree issue.

If I look at the previous issue in MoI, here's what I have using the default settings :



I can see a small issue (red area), but nothing like those black triangles and other ugly shading variation like you show in 3dsmax.




As Michael suggest, giving it a bit more room (lower angle, divide larger than) produce much better render mesh. Even if you can consider the triangulation not 'optimal', I can't find any glitches or visual imperfection looking at the shading view alone. This is exactly how my model look's like in my DCC, Moi doesn't hide or enhance anything.

Image Attachments:
_XP01.JPG  _XP02.JPG  _XP03.JPG  _XP04.JPG 

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@Michael Gibson

>>Low poly artifacts like that will just generally be what you can expect if you are trying to restrict polygon count.
The main way to make polygons adapt to the fillet's curvature better is to move the slider towards the right so it will have more subdivisions in curved areas.
I don't really understand why you refuse to do that?

Because I'm from Archviz field and usually my projects (hotels, malls, city blocks etc) contain **tens of thousands** entourage objects (which I'd like to make in MOI). even using proxies and forest packs we, Archviz monkeys, have to keep poly count discipline.
I attach a screenshot of a typical mesh from some good model maker. Notice 3-5 segments for a fillet, 16-24 segs for cylinder - no more. 24 segments for a fillet (your and PaQ's sujeestions) is not an option in my case,
https://storage.de.cloud.ovh.net/v1/AUTH_cfac7191c3a34a1e9648a2af88284d53/VP_Download_Mirror/catalogs/3D_MALL_EQUIPMENT_catalog.pdf

Image Attachments:
mall chair.png 

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Tweak first "Angle" and (optionally) "divide large than" to get a nice overall resolution on high curvature area (silhouette).
You can then use "Avoid smaller than" this remove excessive geometry in fillet area.

This alone will already produce a mesh lighter than the default angle 12, with better silhouette, and good quality surface.



A poly reduce in your DCC (according it preserve vertex normals) can be a last touch.


Left : default export value (6500 tris), Middle : "optimized" one using advanced MoI settings (4900 tris), Right : polyreduced-LOD (2440 tris).

I hardly see any difference, the middle model will handle close-up way better tho.

If you expect low poly game asset where every triangle "count", using a CAD mesher is probably not the ideal tool. Imho MoI provides a lots of control over the mesh quality with a comprehensible set of options, it's just the best for the task. I had no shame to produce game assets using it, even tho it was only for prototype content. But yes you have to give up on what you usually produce by manually poly modelling assets, as you don't have direct control over the topology.

Image Attachments:
_XP_02.JPG  _XP_03.JPG 

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Hi rom, maybe I can detect these kind of n-gons and do some additional refinement just on them.

- Michael

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@PaQ thank you, of course I use it, and lately folks at Autodesk put lots of efforts to improve the Retopo modifier. There're hints that they will push it even further.
https://www.youtube.com/watch?v=qtj3rvL2pUI&t=161s
But its still doesn't mean Moi's exporter can't be improved :)

>>Hi rom, maybe I can detect these kind of n-gons and do some additional refinement just on them.
Awesome Michael, thank you for attention

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