Blender Quad + edge + low poly = topology problem

neoshaman · Nov 2009

Hello!

This is my first post (help!) here. I have been attract in this forum 'cause of the excellent thred about low poly under 500 tri, which i often use to plead my cause about less poly and more design

I was particulary geek out when it finally reach its 128 mark (waiting now for the 256). That and many other insightful thread all around.

I'm a game developer who just start making game (before i was just a gamedesigner) for its local area (martinique, french west indies) which is pretty small as a market. As i could not afford to pay a graphist (or could find someone competant and foolish enough to start working for free) i have started learning 3D low poly modeling.

I use blender and learned quickly the basics but got some problem with topology when using quad. Sometime the "hidden edge" of a quad is not in the right direction and give a nasty look to my topology. The only way of getting rid of this is to kill the quad and reconstruct triangle with the correct orientation, then merge them back into a quad. But this is really expensive when you have to fix the whole model.

I know in 3DSmax you could see those edge in the quad and have an option to "edge turn" them. But now i could not afford to pay a full license for max (i'm way too poor). I have try to investigate many other free 3D low poly modeling option but could find a decent one with edge turn. I have read entire manual and browse the net, but no one seems to care.

Is there an option in blender to that i may have miss or a more appropriate 3D package for my need? or maybe i should consider different modeling practice?

Neavah · Nov 2009

Here's a link to a forum where they talk about this, I'm assuming their question is what your doing, and the first response is an easier way of doing it...

http://blenderartists.org/forum/showthread.php?t=97633

Hope that helps!

jrs100000 · Nov 2009

If I understand your question correctly, what youll want to do is: enter edit mode, select the faces that you want to flip, and press Ctril+Shift+F to flip the triangle edges. You can also find this command in edit mode under the Mesh->Faces menu.

neoshaman · Nov 2009

Great thanks!

But it seems that the problem is even more complicated as seen on this particular thread : http://blenderartists.org/forum/showthread.php?t=73527

Orinoco wrote:

understand why you feel that way, but the "hidden" edge you see is undefined by Blender, so the render engine or the graphics card you use puts one in according to whatever algorithm it uses. Try experimenting with a simple low poly shape: I've found the "hidden" edge changes if I switch from Windows to Linux, or if I switch between the openGL 3D view and the internal render engine. If there were a hidden edge that could be manipulated by modeling techniques, this wouldn't be the case.

[...]

I've seen that happen, a lot. Not only that, but if you move that blend file to a machine with a different video card or a different operating system, chances are good that the images would be different.

I don't program for Blender, so anyone who does: feel free to chime in here and correct any misinterpretations I have, but here's what I think is going on:

Hardware graphic 3d cards operate on triangles: all tris, all the time. As someone said in an earlier thread, "under the hood, its all tris." Some 3d packages operate the same way, but, because triangles are hard to model with, they added code that says, in effect: "don't show the common edge between these triangles" and they then have quads. And pentagons, hexagons, and other multi-triangle n-gons. But since the edges are there in the mesh database, and, as "real" edges they affect shape, the user is given a way to rearrange the invisible common edge.

Blender, on the other hand, implemented quads directly. A quad isn't just two tris with an invisible edge. However, as Blender displays meshes using 3d graphics cards, and renders them using render engines, at some point the quad is converted into two triangles. There is obviously more than one way to do this conversion, or the renders would always match the 3d view, and they don't. So if you do something to the mesh that affects the underlying data in such a way as to change the tri conversion, you have, for your system, turned the edge. Unfortunately, an edge turned in 3D view may not also be a turned edge in the rendered image. Or it might. But only on your system, and others exactly like it.

Anyway, that's my story... and I'm sticking to it.

There is image proof of the problem made by Spacemonkey!

Conclusion: Blender + quad = Bad low poly topology control

I'm trying Gmax, but it seems i could not create usable format (what is this .P3D anyway >:( )
Anim8or does not flip quad edge either...
Is there a good modeling package for low poly?

Lamoot · Nov 2009

With really low poly stuff, you're still better off converting the quad to tris and manually set the edges exactly the way you want them. Comandeer the triangularization so to speak

As for free modelling software you could try:

wings3d
softimage mod tool (if it's still available after Autodek bought the original package)
continue to use Blender and manually set the problematic edges

Don't know any other free modelling programs worth recomending.

neoshaman · Dec 2009

Wings 3D check!

Doc seems aware of internal quad edge, but do not provide tool to deal with...

I'll stick to blender for a while.

Thanks

kat · Dec 2009

The tools to deal with this are... edit mode, Ctrl+T to tessellate, Ctrl+Shift+F to 'turn', Alf+J to convert back to quad. Generally speaking once you do that the quad keeps it's turned edge orientation.

neoshaman · Dec 2009

Yep but try a render or an export, and then the quad will be ramdomly tesselate

But i made think that you are actually giving a really good advice >> on edit create good topology, before rendering or exporting >> convert to tri to keep the topology

Thanks

kat · Dec 2009

I can't speak for rendering as I don't really use Blender for that/it's not that important to me. But for exporting, once you've flipped the edge like that it should stay put even if you re-tessellate the face to triangles after doing this to it; I've not had or noticed any major issues with this myself and that's on all sorts of mesh work for all sorts of purposes.

This is one of the reasons you should manually tessellate the mesh before exporting for game, rather than replying on the export scripts available, to ensure edges/faces are rotated correctly.

Blender Quad + edge + low poly = topology problem

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