Circular Alternative

[bnewton81]

I was just thinking on an alternative to the standard closed circle mesh of triangles joined at a single vert in the center. The problem is that they are harder to texture and can often cause artifacts. Well I was just thinking that wouldn't it be easier to create a "hoop", and close it by creating a plane and using alpha blend to make the area outside the hoop invisible? Know what I mean?

[Calena]

It sort of depends on what you're trying to create. What you're describing sounds like placing a circle on top of a plane. Andy's tutorial on blending describes something like this. There are actually all sorts of ways to do this. The easiest and simplest for me is to create the circular graphic in a 2D program (I'm using gimp), save it as a .png file with the alpha layer and then map that to my mesh. As far as the mesh itself, there are other ways of creating the circle besides the standard 'pie' shape. You can use Cntl F to get a criss-cross fill or for high resolution, use a bezier circle then convert it to a mesh.

The BEST way to solve this is to get really good at UV mapping . I'm still finding better, faster and easier ways to do this. The more I do it, the more I appreciate what a powerful tool it can be.

[tachzusamm]

I would not recommend to use blending just to camouflage triangle problems.

My suggestion for constructing circles (left) and rounded holes (right) in a well planned way:

circles.png (13.39 KiB) Viewed 3729 times

Advantage: Uses only quads.

The construction of course depends on the number of verticies the circle should have. Use numbers you can divide by 4.

[Calena]

Tach does it again. I'm sitting here scratching my head, dissecting your circle to figure out how you did that! I'm thinking the easiest way is to intersect a plane with a sphere and use "Difference" to cut the hole. The other one looks like adding a circle with 8 vertices, extrude it, fill the center with quads, then add a second circle on the outside with 24 vertices and join the two meshes. Am I even remotely close?

BTW, this has nothing to do with UV mapping. which is what the question is about. We still have to map to the outside vertices. The inside is irrelevant. Where Tach's circle can make a huge difference is in vertex painting or in more advanced UV mapping where each face is individually mapped.

Excuse me while I go off to learn how to make a circle all over again .

[Jojon]

If it comes to UV-mapping those quads individually, as mentioned, it may be worth keeping in mind that neither Blender nor Plasma actually does treat quads as actual quads.

Instead you'll need to picture each of the quads in tachzusamm's picture bisected by a diagonal edge -- they are all in truth two triangles - it's just that you do not see the one edge in the editor, even though you will see its auto-applied effect, if you make the quad non-flat.

That means that your texture will not stretch between the four corners of the quad, but between the two shared plus two private ones of two tris, so if the quad does not have 90 degree corners, you may need to make sure your patch of texture does have the general shape of the quad, in order to avoid distortion.


...hope that was somewhat legible... I confuse myself, most of the time...

[tachzusamm]

Just for fun, I recorded how I filled the circle:
http://www.youtube.com/watch?v=F8bF9HbRyWk

The faces are simply filled by pressing F when 4 verticies are selected.

Jojon is right, neither Blender nor Plasma renders quads; they get converted to triangles (tris). The only advantage when using quads that it's much easier to further process the mesh, e.g. to insert loop cuts to deform it a bit more (which is impossible if you work with tris); and unwrapping using "follow active quads" is possible only with quads of course. Plus, if you want to smooth your mesh a bit more, subsurf works well if you have quads; having tris is a bit of a mess.

[bnewton81]

This is exactly the info I was looking for.