Hey Max!
The difference between Quads and Tris is as the name suggests, Quads have four vertices/edges, tris have only three.
Quads are preferred over Tris or Ngons (a Face with Five or more vertices/edges) because of many tools, modifiers and textures can have adverse effects with Tris and Ngons.
For example, the Loop Cut tool (CTRL+R) doesn't cut through Tris or Ngons, Tris with a subsurf modifier can cause pinching.
Quads and Tris are not completely forbidden, however. They can still be used for speed and convenience. It all depends on what and how you are going to use the model.
Hope this helps!
thx. I asked cause it's less of a headache to just make tris. I don't have a clue how to create quads in certain type of topology that you have to change later on.
One more question: Is it better to use the knife tool to make quads instead of using the vertices that are already there to make quads?
All it does is that it adds vertices, but you can make quads easily.
Whether you use quads or tris (or n-gons) (on non-planar geometry) makes a difference when using a Subsurf Modifier:
The same is true when you make quads (with the Knife Tool) using more Vertices; the resulting shape could be different.
So it depends on what you want. Not so much which tools you use, but the resulting Topology is important.
If you find it easier, you can use the Knife Tool and maybe (if necessary) Merge some of the extra Vertices...
Yeah you can make a quad with any of the tools, no problem. You can also use F to fill a face or construct it from nothing adding a single vertex with Control + click. There are other tools, all of them valuable and ok to use. Remember, you can use triangles or Ngons for convenience, but you have to be really careful and mindful of where to put them, you can't just use them anywhere. I recommend you stick to quads, so you start getting used to how tricky it is to make a mesh quads only. Then after you know the rules and how to implement them, you can start to break them.
So in your example, we can see that it's a sphere, but you added am edge. It change the shape. I also notice that if you add a single vertice on a edge that is completely useless, it change the shape...?? But it should not. Why? Because it influence the subsurf?
Omar, I noticed that we can do whatever we want on a planar surface. That is one of the exception.
How to add a single vertice? CTRL + left mouse button?? I used to use subdivide. Is there a shortcut, a better way?
Yes, planar surfaces is the exception.
And yes, to add a single vertex, in edit mode, if you control right click a single vertex gets added at the position of your mouse. If you continue doing this, more vertices will be created chained together by edges. If you do the same thing but with a face selected, it will extrude that face to where you have your mouse placed.
I also notice that if you add a single vertice on a edge that is completely useless, it change the shape...?? But it should not. Why? Because the it influence the subsurf?
Yes, that is because of the Catmull-Clark algorithm, that uses the 'centers' of Faces, which are calculated by taking the average of the Vertices that make up that Face and adding a Vertex changes the position of that 'Face center':
