Avoiding twisted quads

Hi everyone. It’s my first time back here in 3 years. I was doing good learning to model, but UV mapping and other texturing methods came along and kicked my butt, so I sort of lost interest.

Anyway, I’m back and with a new newbie question:

Are twisted quads something we should avoid? I’ve been trying to model a low-poly robot (for a game I hope to one day create), and it seems like no matter what I do, I end up with a bunch of twisted quads. The only way it seems I can avoid this is by manipulating 2 vertices at once every time I need to change something… but that can’t always be done. This is driving me nuts.

Here’s an example I grabbed off google images:
http://www.petaimg.com/uploads/1226895773.jpg

That picture is a little extreme, but it illustrates what I’m talking about. Anyone have any tips on this?

Thanks!

Quads were meant to be twisted. If you go extreme low poly, as your example, you will want to build the warped part out of triangles, so you can determine which corners the crease runs between. But for the most part, don’t worry about it. Getting the topology right is more of an issue, but there are new tools in the last three years that make fixing topology easier, too.

So if the twisting isn’t too extreme, it’s OK? I always hear people harping on about how much better quads are than triangles… but in cases like this, is there anything wrong with mixing a few triangles in with a mostly quad-based model?

Here’s an example of a mech foot I just started messing with. And alas, as always I ended up with accidentally twisted quads. The arrows indicate the visibly malformed quads.

http://www.petaimg.com/uploads/1226930127.png

well are the twisting quads doing anything wrong by being there? unless you want that side to be perfectly flat, i don’t see what the problem is. a quad has the same final effect as two triangles, and in my opinion, it’s much cleaner and easier to work with.

Here’s the problem: when you twist a quad, the operating system/graphics card chooses which diagonal to use to bend the quad. Move the mesh to another graphics card/os, and the model may change shape if the other diagonal is used instead. You, as the modeler, have no control over which it is, unless you model the part with two triangles instead of a single quad, since then you get to choose which diagonal acts as the hinge.

People harp about using quads instead of triangles, because they don’t build models with perfectly flat planes and perfectly sharp edges. They use Blender’s smoothing algorithms to smooth out the sharp edges, and those algorithms work best with quads. Triangles can cause unsightly artifacts when the model is rendered, and can cause flickering if the model is animated. Not a good thing.

This is usually only an issue when dealing with very low poly game models, which are normally converted to all tris before being used anyway.

@BlenderNewb101
No, it doesn’t really cause issues… but I was worried whatever is being used to render a twisted quad might get a little confused in the process and render it incorrectly. Since I’m new to 3D and game development in general, I wanted to make sure I’m doing everything right from the get-go to avoid future issues.

@Orinoco
Thanks for the reply, that helps a lot.